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5ba3f43e | 1 | /* |
cb323159 | 2 | * Copyright (c) 2007-2018 Apple Inc. All rights reserved. |
5ba3f43e A |
3 | * |
4 | * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ | |
5 | * | |
6 | * This file contains Original Code and/or Modifications of Original Code | |
7 | * as defined in and that are subject to the Apple Public Source License | |
8 | * Version 2.0 (the 'License'). You may not use this file except in | |
9 | * compliance with the License. The rights granted to you under the License | |
10 | * may not be used to create, or enable the creation or redistribution of, | |
11 | * unlawful or unlicensed copies of an Apple operating system, or to | |
12 | * circumvent, violate, or enable the circumvention or violation of, any | |
13 | * terms of an Apple operating system software license agreement. | |
14 | * | |
15 | * Please obtain a copy of the License at | |
16 | * http://www.opensource.apple.com/apsl/ and read it before using this file. | |
17 | * | |
18 | * The Original Code and all software distributed under the License are | |
19 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER | |
20 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, | |
21 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, | |
22 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. | |
23 | * Please see the License for the specific language governing rights and | |
24 | * limitations under the License. | |
25 | * | |
26 | * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ | |
27 | */ | |
28 | /* | |
29 | * @OSF_COPYRIGHT@ | |
30 | */ | |
31 | /* | |
32 | * Mach Operating System Copyright (c) 1991,1990,1989,1988,1987 Carnegie | |
33 | * Mellon University All Rights Reserved. | |
0a7de745 | 34 | * |
5ba3f43e A |
35 | * Permission to use, copy, modify and distribute this software and its |
36 | * documentation is hereby granted, provided that both the copyright notice | |
37 | * and this permission notice appear in all copies of the software, | |
38 | * derivative works or modified versions, and any portions thereof, and that | |
39 | * both notices appear in supporting documentation. | |
0a7de745 | 40 | * |
5ba3f43e A |
41 | * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" CONDITION. |
42 | * CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR ANY DAMAGES | |
43 | * WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. | |
0a7de745 | 44 | * |
5ba3f43e | 45 | * Carnegie Mellon requests users of this software to return to |
0a7de745 | 46 | * |
5ba3f43e A |
47 | * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU |
48 | * School of Computer Science Carnegie Mellon University Pittsburgh PA | |
49 | * 15213-3890 | |
0a7de745 | 50 | * |
5ba3f43e A |
51 | * any improvements or extensions that they make and grant Carnegie Mellon the |
52 | * rights to redistribute these changes. | |
53 | */ | |
54 | /* | |
55 | * File: kern/lock.c | |
56 | * Author: Avadis Tevanian, Jr., Michael Wayne Young | |
57 | * Date: 1985 | |
58 | * | |
59 | * Locking primitives implementation | |
60 | */ | |
61 | ||
5ba3f43e A |
62 | #define LOCK_PRIVATE 1 |
63 | ||
64 | #include <mach_ldebug.h> | |
65 | ||
f427ee49 | 66 | #include <kern/zalloc.h> |
0a7de745 | 67 | #include <kern/lock_stat.h> |
5ba3f43e A |
68 | #include <kern/locks.h> |
69 | #include <kern/misc_protos.h> | |
70 | #include <kern/thread.h> | |
71 | #include <kern/processor.h> | |
72 | #include <kern/sched_prim.h> | |
5ba3f43e A |
73 | #include <kern/debug.h> |
74 | #include <kern/kcdata.h> | |
75 | #include <string.h> | |
ea3f0419 A |
76 | #include <arm/cpu_internal.h> |
77 | #include <os/hash.h> | |
78 | #include <arm/cpu_data.h> | |
5ba3f43e A |
79 | |
80 | #include <arm/cpu_data_internal.h> | |
81 | #include <arm/proc_reg.h> | |
82 | #include <arm/smp.h> | |
83 | #include <machine/atomic.h> | |
84 | #include <machine/machine_cpu.h> | |
85 | ||
86 | #include <sys/kdebug.h> | |
87 | ||
0a7de745 A |
88 | #if CONFIG_DTRACE |
89 | #define DTRACE_RW_SHARED 0x0 //reader | |
90 | #define DTRACE_RW_EXCL 0x1 //writer | |
91 | #define DTRACE_NO_FLAG 0x0 //not applicable | |
92 | #endif /* CONFIG_DTRACE */ | |
5ba3f43e | 93 | |
0a7de745 A |
94 | #define LCK_RW_LCK_EXCLUSIVE_CODE 0x100 |
95 | #define LCK_RW_LCK_EXCLUSIVE1_CODE 0x101 | |
96 | #define LCK_RW_LCK_SHARED_CODE 0x102 | |
97 | #define LCK_RW_LCK_SH_TO_EX_CODE 0x103 | |
98 | #define LCK_RW_LCK_SH_TO_EX1_CODE 0x104 | |
99 | #define LCK_RW_LCK_EX_TO_SH_CODE 0x105 | |
5ba3f43e A |
100 | |
101 | ||
0a7de745 | 102 | #define ANY_LOCK_DEBUG (USLOCK_DEBUG || LOCK_DEBUG || MUTEX_DEBUG) |
5ba3f43e A |
103 | |
104 | // Panic in tests that check lock usage correctness | |
105 | // These are undesirable when in a panic or a debugger is runnning. | |
106 | #define LOCK_CORRECTNESS_PANIC() (kernel_debugger_entry_count == 0) | |
107 | ||
0a7de745 A |
108 | #define ADAPTIVE_SPIN_ENABLE 0x1 |
109 | ||
0a7de745 | 110 | int lck_mtx_adaptive_spin_mode = ADAPTIVE_SPIN_ENABLE; |
0a7de745 A |
111 | |
112 | #define SPINWAIT_OWNER_CHECK_COUNT 4 | |
113 | ||
114 | typedef enum { | |
115 | SPINWAIT_ACQUIRED, /* Got the lock. */ | |
116 | SPINWAIT_INTERLOCK, /* Got the interlock, no owner, but caller must finish acquiring the lock. */ | |
ea3f0419 A |
117 | SPINWAIT_DID_SPIN_HIGH_THR, /* Got the interlock, spun, but failed to get the lock. */ |
118 | SPINWAIT_DID_SPIN_OWNER_NOT_CORE, /* Got the interlock, spun, but failed to get the lock. */ | |
119 | SPINWAIT_DID_SPIN_NO_WINDOW_CONTENTION, /* Got the interlock, spun, but failed to get the lock. */ | |
120 | SPINWAIT_DID_SPIN_SLIDING_THR,/* Got the interlock, spun, but failed to get the lock. */ | |
0a7de745 A |
121 | SPINWAIT_DID_NOT_SPIN, /* Got the interlock, did not spin. */ |
122 | } spinwait_result_t; | |
123 | ||
f427ee49 | 124 | #if CONFIG_DTRACE |
5ba3f43e A |
125 | extern uint64_t dtrace_spin_threshold; |
126 | #endif | |
127 | ||
128 | /* Forwards */ | |
129 | ||
5ba3f43e A |
130 | extern unsigned int not_in_kdp; |
131 | ||
132 | /* | |
133 | * We often want to know the addresses of the callers | |
134 | * of the various lock routines. However, this information | |
135 | * is only used for debugging and statistics. | |
136 | */ | |
137 | typedef void *pc_t; | |
0a7de745 A |
138 | #define INVALID_PC ((void *) VM_MAX_KERNEL_ADDRESS) |
139 | #define INVALID_THREAD ((void *) VM_MAX_KERNEL_ADDRESS) | |
5ba3f43e | 140 | |
0a7de745 | 141 | #ifdef lint |
5ba3f43e A |
142 | /* |
143 | * Eliminate lint complaints about unused local pc variables. | |
144 | */ | |
0a7de745 A |
145 | #define OBTAIN_PC(pc, l) ++pc |
146 | #else /* lint */ | |
147 | #define OBTAIN_PC(pc, l) | |
148 | #endif /* lint */ | |
5ba3f43e A |
149 | |
150 | ||
151 | /* | |
152 | * Portable lock package implementation of usimple_locks. | |
153 | */ | |
154 | ||
5ba3f43e A |
155 | /* |
156 | * Owner thread pointer when lock held in spin mode | |
157 | */ | |
158 | #define LCK_MTX_SPIN_TAG 0xfffffff0 | |
159 | ||
160 | ||
0a7de745 A |
161 | #define interlock_lock(lock) hw_lock_bit ((hw_lock_bit_t*)(&(lock)->lck_mtx_data), LCK_ILOCK_BIT, LCK_GRP_NULL) |
162 | #define interlock_try(lock) hw_lock_bit_try((hw_lock_bit_t*)(&(lock)->lck_mtx_data), LCK_ILOCK_BIT, LCK_GRP_NULL) | |
163 | #define interlock_unlock(lock) hw_unlock_bit ((hw_lock_bit_t*)(&(lock)->lck_mtx_data), LCK_ILOCK_BIT) | |
164 | #define lck_rw_ilk_lock(lock) hw_lock_bit ((hw_lock_bit_t*)(&(lock)->lck_rw_tag), LCK_RW_INTERLOCK_BIT, LCK_GRP_NULL) | |
165 | #define lck_rw_ilk_unlock(lock) hw_unlock_bit((hw_lock_bit_t*)(&(lock)->lck_rw_tag), LCK_RW_INTERLOCK_BIT) | |
5ba3f43e | 166 | |
cb323159 | 167 | #define load_memory_barrier() os_atomic_thread_fence(acquire) |
5ba3f43e A |
168 | |
169 | // Enforce program order of loads and stores. | |
cb323159 A |
170 | #define ordered_load(target) \ |
171 | os_atomic_load(target, compiler_acq_rel) | |
172 | #define ordered_store(target, value) \ | |
173 | os_atomic_store(target, value, compiler_acq_rel) | |
174 | ||
175 | #define ordered_load_mtx(lock) ordered_load(&(lock)->lck_mtx_data) | |
176 | #define ordered_store_mtx(lock, value) ordered_store(&(lock)->lck_mtx_data, (value)) | |
177 | #define ordered_load_rw(lock) ordered_load(&(lock)->lck_rw_data) | |
178 | #define ordered_store_rw(lock, value) ordered_store(&(lock)->lck_rw_data, (value)) | |
179 | #define ordered_load_rw_owner(lock) ordered_load(&(lock)->lck_rw_owner) | |
180 | #define ordered_store_rw_owner(lock, value) ordered_store(&(lock)->lck_rw_owner, (value)) | |
181 | #define ordered_load_hw(lock) ordered_load(&(lock)->lock_data) | |
182 | #define ordered_store_hw(lock, value) ordered_store(&(lock)->lock_data, (value)) | |
183 | #define ordered_load_bit(lock) ordered_load((lock)) | |
184 | #define ordered_store_bit(lock, value) ordered_store((lock), (value)) | |
5ba3f43e A |
185 | |
186 | ||
187 | // Prevent the compiler from reordering memory operations around this | |
0a7de745 | 188 | #define compiler_memory_fence() __asm__ volatile ("" ::: "memory") |
5ba3f43e | 189 | |
0a7de745 A |
190 | #define LOCK_PANIC_TIMEOUT 0xc00000 |
191 | #define NOINLINE __attribute__((noinline)) | |
5ba3f43e A |
192 | |
193 | ||
194 | #if __arm__ | |
195 | #define interrupts_disabled(mask) (mask & PSR_INTMASK) | |
196 | #else | |
197 | #define interrupts_disabled(mask) (mask & DAIF_IRQF) | |
198 | #endif | |
199 | ||
200 | ||
201 | #if __arm__ | |
0a7de745 A |
202 | #define enable_fiq() __asm__ volatile ("cpsie f" ::: "memory"); |
203 | #define enable_interrupts() __asm__ volatile ("cpsie if" ::: "memory"); | |
5ba3f43e A |
204 | #endif |
205 | ||
f427ee49 A |
206 | ZONE_VIEW_DEFINE(ZV_LCK_SPIN, "lck_spin", |
207 | KHEAP_ID_DEFAULT, sizeof(lck_spin_t)); | |
208 | ||
209 | ZONE_VIEW_DEFINE(ZV_LCK_MTX, "lck_mtx", | |
210 | KHEAP_ID_DEFAULT, sizeof(lck_mtx_t)); | |
211 | ||
212 | ZONE_VIEW_DEFINE(ZV_LCK_MTX_EXT, "lck_mtx_ext", | |
213 | KHEAP_ID_DEFAULT, sizeof(lck_mtx_ext_t)); | |
214 | ||
215 | ZONE_VIEW_DEFINE(ZV_LCK_RW, "lck_rw", | |
216 | KHEAP_ID_DEFAULT, sizeof(lck_rw_t)); | |
217 | ||
5ba3f43e A |
218 | /* |
219 | * Forward declarations | |
220 | */ | |
221 | ||
222 | static void lck_rw_lock_shared_gen(lck_rw_t *lck); | |
223 | static void lck_rw_lock_exclusive_gen(lck_rw_t *lck); | |
224 | static boolean_t lck_rw_lock_shared_to_exclusive_success(lck_rw_t *lck); | |
225 | static boolean_t lck_rw_lock_shared_to_exclusive_failure(lck_rw_t *lck, uint32_t prior_lock_state); | |
226 | static void lck_rw_lock_exclusive_to_shared_gen(lck_rw_t *lck, uint32_t prior_lock_state); | |
227 | static lck_rw_type_t lck_rw_done_gen(lck_rw_t *lck, uint32_t prior_lock_state); | |
5ba3f43e A |
228 | static boolean_t lck_rw_grab(lck_rw_t *lock, int mode, boolean_t wait); |
229 | ||
230 | /* | |
231 | * atomic exchange API is a low level abstraction of the operations | |
232 | * to atomically read, modify, and write a pointer. This abstraction works | |
233 | * for both Intel and ARMv8.1 compare and exchange atomic instructions as | |
234 | * well as the ARM exclusive instructions. | |
235 | * | |
236 | * atomic_exchange_begin() - begin exchange and retrieve current value | |
237 | * atomic_exchange_complete() - conclude an exchange | |
238 | * atomic_exchange_abort() - cancel an exchange started with atomic_exchange_begin() | |
239 | */ | |
cb323159 A |
240 | __unused static uint32_t |
241 | load_exclusive32(uint32_t *target, enum memory_order ord) | |
242 | { | |
243 | uint32_t value; | |
244 | ||
245 | #if __arm__ | |
f427ee49 | 246 | if (_os_atomic_mo_has_release(ord)) { |
cb323159 A |
247 | // Pre-load release barrier |
248 | atomic_thread_fence(memory_order_release); | |
249 | } | |
250 | value = __builtin_arm_ldrex(target); | |
251 | #else | |
f427ee49 | 252 | if (_os_atomic_mo_has_acquire(ord)) { |
cb323159 A |
253 | value = __builtin_arm_ldaex(target); // ldaxr |
254 | } else { | |
255 | value = __builtin_arm_ldrex(target); // ldxr | |
256 | } | |
257 | #endif // __arm__ | |
258 | return value; | |
259 | } | |
260 | ||
261 | __unused static boolean_t | |
262 | store_exclusive32(uint32_t *target, uint32_t value, enum memory_order ord) | |
263 | { | |
264 | boolean_t err; | |
265 | ||
266 | #if __arm__ | |
267 | err = __builtin_arm_strex(value, target); | |
f427ee49 | 268 | if (_os_atomic_mo_has_acquire(ord)) { |
cb323159 A |
269 | // Post-store acquire barrier |
270 | atomic_thread_fence(memory_order_acquire); | |
271 | } | |
272 | #else | |
f427ee49 | 273 | if (_os_atomic_mo_has_release(ord)) { |
cb323159 A |
274 | err = __builtin_arm_stlex(value, target); // stlxr |
275 | } else { | |
276 | err = __builtin_arm_strex(value, target); // stxr | |
277 | } | |
278 | #endif // __arm__ | |
279 | return !err; | |
280 | } | |
281 | ||
5ba3f43e A |
282 | static uint32_t |
283 | atomic_exchange_begin32(uint32_t *target, uint32_t *previous, enum memory_order ord) | |
284 | { | |
0a7de745 | 285 | uint32_t val; |
5ba3f43e | 286 | |
cb323159 A |
287 | #if __ARM_ATOMICS_8_1 |
288 | ord = memory_order_relaxed; | |
289 | #endif | |
5ba3f43e A |
290 | val = load_exclusive32(target, ord); |
291 | *previous = val; | |
292 | return val; | |
293 | } | |
294 | ||
295 | static boolean_t | |
296 | atomic_exchange_complete32(uint32_t *target, uint32_t previous, uint32_t newval, enum memory_order ord) | |
297 | { | |
cb323159 A |
298 | #if __ARM_ATOMICS_8_1 |
299 | return __c11_atomic_compare_exchange_strong((_Atomic uint32_t *)target, &previous, newval, ord, memory_order_relaxed); | |
300 | #else | |
0a7de745 | 301 | (void)previous; // Previous not needed, monitor is held |
5ba3f43e | 302 | return store_exclusive32(target, newval, ord); |
cb323159 | 303 | #endif |
5ba3f43e A |
304 | } |
305 | ||
306 | static void | |
307 | atomic_exchange_abort(void) | |
308 | { | |
cb323159 | 309 | os_atomic_clear_exclusive(); |
5ba3f43e A |
310 | } |
311 | ||
312 | static boolean_t | |
313 | atomic_test_and_set32(uint32_t *target, uint32_t test_mask, uint32_t set_mask, enum memory_order ord, boolean_t wait) | |
314 | { | |
0a7de745 | 315 | uint32_t value, prev; |
5ba3f43e | 316 | |
0a7de745 | 317 | for (;;) { |
5ba3f43e A |
318 | value = atomic_exchange_begin32(target, &prev, ord); |
319 | if (value & test_mask) { | |
0a7de745 A |
320 | if (wait) { |
321 | wait_for_event(); // Wait with monitor held | |
322 | } else { | |
323 | atomic_exchange_abort(); // Clear exclusive monitor | |
324 | } | |
5ba3f43e A |
325 | return FALSE; |
326 | } | |
327 | value |= set_mask; | |
0a7de745 | 328 | if (atomic_exchange_complete32(target, prev, value, ord)) { |
5ba3f43e | 329 | return TRUE; |
0a7de745 | 330 | } |
5ba3f43e A |
331 | } |
332 | } | |
333 | ||
cb323159 A |
334 | inline boolean_t |
335 | hw_atomic_test_and_set32(uint32_t *target, uint32_t test_mask, uint32_t set_mask, enum memory_order ord, boolean_t wait) | |
336 | { | |
337 | return atomic_test_and_set32(target, test_mask, set_mask, ord, wait); | |
338 | } | |
339 | ||
f427ee49 A |
340 | /* |
341 | * To help _disable_preemption() inline everywhere with LTO, | |
342 | * we keep these nice non inlineable functions as the panic() | |
343 | * codegen setup is quite large and for weird reasons causes a frame. | |
344 | */ | |
345 | __abortlike | |
346 | static void | |
347 | _disable_preemption_overflow(void) | |
348 | { | |
349 | panic("Preemption count overflow"); | |
350 | } | |
351 | ||
0a7de745 A |
352 | void |
353 | _disable_preemption(void) | |
5ba3f43e | 354 | { |
cb323159 A |
355 | thread_t thread = current_thread(); |
356 | unsigned int count = thread->machine.preemption_count; | |
5ba3f43e | 357 | |
f427ee49 A |
358 | if (__improbable(++count == 0)) { |
359 | _disable_preemption_overflow(); | |
cb323159 A |
360 | } |
361 | ||
362 | os_atomic_store(&thread->machine.preemption_count, count, compiler_acq_rel); | |
5ba3f43e A |
363 | } |
364 | ||
cb323159 A |
365 | /* |
366 | * This function checks whether an AST_URGENT has been pended. | |
367 | * | |
368 | * It is called once the preemption has been reenabled, which means the thread | |
369 | * may have been preempted right before this was called, and when this function | |
370 | * actually performs the check, we've changed CPU. | |
371 | * | |
372 | * This race is however benign: the point of AST_URGENT is to trigger a context | |
373 | * switch, so if one happened, there's nothing left to check for, and AST_URGENT | |
374 | * was cleared in the process. | |
375 | * | |
376 | * It follows that this check cannot have false negatives, which allows us | |
377 | * to avoid fiddling with interrupt state for the vast majority of cases | |
378 | * when the check will actually be negative. | |
379 | */ | |
380 | static NOINLINE void | |
381 | kernel_preempt_check(thread_t thread) | |
5ba3f43e | 382 | { |
cb323159 A |
383 | cpu_data_t *cpu_data_ptr; |
384 | long state; | |
385 | ||
5ba3f43e A |
386 | #if __arm__ |
387 | #define INTERRUPT_MASK PSR_IRQF | |
0a7de745 | 388 | #else // __arm__ |
5ba3f43e | 389 | #define INTERRUPT_MASK DAIF_IRQF |
0a7de745 | 390 | #endif // __arm__ |
5ba3f43e | 391 | |
cb323159 A |
392 | /* |
393 | * This check is racy and could load from another CPU's pending_ast mask, | |
394 | * but as described above, this can't have false negatives. | |
395 | */ | |
396 | cpu_data_ptr = os_atomic_load(&thread->machine.CpuDatap, compiler_acq_rel); | |
397 | if (__probable((cpu_data_ptr->cpu_pending_ast & AST_URGENT) == 0)) { | |
398 | return; | |
0a7de745 | 399 | } |
cb323159 A |
400 | |
401 | /* If interrupts are masked, we can't take an AST here */ | |
402 | state = get_interrupts(); | |
403 | if ((state & INTERRUPT_MASK) == 0) { | |
404 | disable_interrupts_noread(); // Disable interrupts | |
405 | ||
406 | /* | |
407 | * Reload cpu_data_ptr: a context switch would cause it to change. | |
408 | * Now that interrupts are disabled, this will debounce false positives. | |
409 | */ | |
410 | cpu_data_ptr = os_atomic_load(&thread->machine.CpuDatap, compiler_acq_rel); | |
411 | if (thread->machine.CpuDatap->cpu_pending_ast & AST_URGENT) { | |
5ba3f43e A |
412 | #if __arm__ |
413 | #if __ARM_USER_PROTECT__ | |
cb323159 | 414 | uintptr_t up = arm_user_protect_begin(thread); |
0a7de745 | 415 | #endif // __ARM_USER_PROTECT__ |
cb323159 | 416 | enable_fiq(); |
0a7de745 | 417 | #endif // __arm__ |
cb323159 | 418 | ast_taken_kernel(); // Handle urgent AST |
5ba3f43e A |
419 | #if __arm__ |
420 | #if __ARM_USER_PROTECT__ | |
cb323159 | 421 | arm_user_protect_end(thread, up, TRUE); |
0a7de745 | 422 | #endif // __ARM_USER_PROTECT__ |
cb323159 A |
423 | enable_interrupts(); |
424 | return; // Return early on arm only due to FIQ enabling | |
0a7de745 | 425 | #endif // __arm__ |
0a7de745 | 426 | } |
cb323159 | 427 | restore_interrupts(state); // Enable interrupts |
5ba3f43e | 428 | } |
5ba3f43e | 429 | } |
5ba3f43e | 430 | |
f427ee49 A |
431 | /* |
432 | * To help _enable_preemption() inline everywhere with LTO, | |
433 | * we keep these nice non inlineable functions as the panic() | |
434 | * codegen setup is quite large and for weird reasons causes a frame. | |
435 | */ | |
436 | __abortlike | |
437 | static void | |
438 | _enable_preemption_underflow(void) | |
439 | { | |
440 | panic("Preemption count underflow"); | |
441 | } | |
442 | ||
5ba3f43e | 443 | void |
cb323159 | 444 | _enable_preemption(void) |
5ba3f43e | 445 | { |
cb323159 A |
446 | thread_t thread = current_thread(); |
447 | unsigned int count = thread->machine.preemption_count; | |
5ba3f43e | 448 | |
cb323159 | 449 | if (__improbable(count == 0)) { |
f427ee49 | 450 | _enable_preemption_underflow(); |
0a7de745 | 451 | } |
cb323159 | 452 | count -= 1; |
5ba3f43e | 453 | |
cb323159 A |
454 | os_atomic_store(&thread->machine.preemption_count, count, compiler_acq_rel); |
455 | if (count == 0) { | |
456 | kernel_preempt_check(thread); | |
0a7de745 | 457 | } |
f427ee49 A |
458 | |
459 | os_compiler_barrier(); | |
d9a64523 A |
460 | } |
461 | ||
cb323159 A |
462 | int |
463 | get_preemption_level(void) | |
d9a64523 | 464 | { |
cb323159 | 465 | return current_thread()->machine.preemption_count; |
d9a64523 | 466 | } |
5ba3f43e A |
467 | |
468 | /* | |
469 | * Routine: lck_spin_alloc_init | |
470 | */ | |
471 | lck_spin_t * | |
472 | lck_spin_alloc_init( | |
0a7de745 A |
473 | lck_grp_t * grp, |
474 | lck_attr_t * attr) | |
5ba3f43e | 475 | { |
f427ee49 | 476 | lck_spin_t *lck; |
5ba3f43e | 477 | |
f427ee49 A |
478 | lck = zalloc(ZV_LCK_SPIN); |
479 | lck_spin_init(lck, grp, attr); | |
0a7de745 | 480 | return lck; |
5ba3f43e A |
481 | } |
482 | ||
483 | /* | |
484 | * Routine: lck_spin_free | |
485 | */ | |
486 | void | |
487 | lck_spin_free( | |
0a7de745 A |
488 | lck_spin_t * lck, |
489 | lck_grp_t * grp) | |
5ba3f43e A |
490 | { |
491 | lck_spin_destroy(lck, grp); | |
f427ee49 | 492 | zfree(ZV_LCK_SPIN, lck); |
5ba3f43e A |
493 | } |
494 | ||
495 | /* | |
496 | * Routine: lck_spin_init | |
497 | */ | |
498 | void | |
499 | lck_spin_init( | |
0a7de745 A |
500 | lck_spin_t * lck, |
501 | lck_grp_t * grp, | |
502 | __unused lck_attr_t * attr) | |
5ba3f43e | 503 | { |
5ba3f43e | 504 | lck->type = LCK_SPIN_TYPE; |
cb323159 A |
505 | hw_lock_init(&lck->hwlock); |
506 | if (grp) { | |
507 | lck_grp_reference(grp); | |
508 | lck_grp_lckcnt_incr(grp, LCK_TYPE_SPIN); | |
509 | } | |
5ba3f43e A |
510 | } |
511 | ||
512 | /* | |
513 | * arm_usimple_lock is a lck_spin_t without a group or attributes | |
514 | */ | |
515 | void inline | |
516 | arm_usimple_lock_init(simple_lock_t lck, __unused unsigned short initial_value) | |
517 | { | |
518 | lck->type = LCK_SPIN_TYPE; | |
519 | hw_lock_init(&lck->hwlock); | |
5ba3f43e A |
520 | } |
521 | ||
522 | ||
523 | /* | |
524 | * Routine: lck_spin_lock | |
525 | */ | |
526 | void | |
527 | lck_spin_lock(lck_spin_t *lock) | |
528 | { | |
0a7de745 A |
529 | #if DEVELOPMENT || DEBUG |
530 | if (lock->type != LCK_SPIN_TYPE) { | |
531 | panic("Invalid spinlock %p", lock); | |
532 | } | |
533 | #endif // DEVELOPMENT || DEBUG | |
534 | hw_lock_lock(&lock->hwlock, LCK_GRP_NULL); | |
535 | } | |
536 | ||
537 | void | |
538 | lck_spin_lock_grp(lck_spin_t *lock, lck_grp_t *grp) | |
539 | { | |
540 | #pragma unused(grp) | |
541 | #if DEVELOPMENT || DEBUG | |
542 | if (lock->type != LCK_SPIN_TYPE) { | |
5ba3f43e | 543 | panic("Invalid spinlock %p", lock); |
0a7de745 A |
544 | } |
545 | #endif // DEVELOPMENT || DEBUG | |
546 | hw_lock_lock(&lock->hwlock, grp); | |
5ba3f43e A |
547 | } |
548 | ||
d9a64523 A |
549 | /* |
550 | * Routine: lck_spin_lock_nopreempt | |
551 | */ | |
552 | void | |
553 | lck_spin_lock_nopreempt(lck_spin_t *lock) | |
554 | { | |
0a7de745 A |
555 | #if DEVELOPMENT || DEBUG |
556 | if (lock->type != LCK_SPIN_TYPE) { | |
557 | panic("Invalid spinlock %p", lock); | |
558 | } | |
559 | #endif // DEVELOPMENT || DEBUG | |
560 | hw_lock_lock_nopreempt(&lock->hwlock, LCK_GRP_NULL); | |
561 | } | |
562 | ||
563 | void | |
564 | lck_spin_lock_nopreempt_grp(lck_spin_t *lock, lck_grp_t *grp) | |
565 | { | |
566 | #pragma unused(grp) | |
567 | #if DEVELOPMENT || DEBUG | |
568 | if (lock->type != LCK_SPIN_TYPE) { | |
d9a64523 | 569 | panic("Invalid spinlock %p", lock); |
0a7de745 A |
570 | } |
571 | #endif // DEVELOPMENT || DEBUG | |
572 | hw_lock_lock_nopreempt(&lock->hwlock, grp); | |
d9a64523 A |
573 | } |
574 | ||
5ba3f43e A |
575 | /* |
576 | * Routine: lck_spin_try_lock | |
577 | */ | |
578 | int | |
579 | lck_spin_try_lock(lck_spin_t *lock) | |
580 | { | |
0a7de745 A |
581 | return hw_lock_try(&lock->hwlock, LCK_GRP_NULL); |
582 | } | |
583 | ||
584 | int | |
585 | lck_spin_try_lock_grp(lck_spin_t *lock, lck_grp_t *grp) | |
586 | { | |
587 | #pragma unused(grp) | |
588 | return hw_lock_try(&lock->hwlock, grp); | |
5ba3f43e A |
589 | } |
590 | ||
d9a64523 A |
591 | /* |
592 | * Routine: lck_spin_try_lock_nopreempt | |
593 | */ | |
594 | int | |
595 | lck_spin_try_lock_nopreempt(lck_spin_t *lock) | |
596 | { | |
0a7de745 A |
597 | return hw_lock_try_nopreempt(&lock->hwlock, LCK_GRP_NULL); |
598 | } | |
599 | ||
600 | int | |
601 | lck_spin_try_lock_nopreempt_grp(lck_spin_t *lock, lck_grp_t *grp) | |
602 | { | |
603 | #pragma unused(grp) | |
604 | return hw_lock_try_nopreempt(&lock->hwlock, grp); | |
d9a64523 A |
605 | } |
606 | ||
5ba3f43e A |
607 | /* |
608 | * Routine: lck_spin_unlock | |
609 | */ | |
610 | void | |
611 | lck_spin_unlock(lck_spin_t *lock) | |
612 | { | |
0a7de745 A |
613 | #if DEVELOPMENT || DEBUG |
614 | if ((LCK_MTX_STATE_TO_THREAD(lock->lck_spin_data) != current_thread()) && LOCK_CORRECTNESS_PANIC()) { | |
5ba3f43e | 615 | panic("Spinlock not owned by thread %p = %lx", lock, lock->lck_spin_data); |
0a7de745 A |
616 | } |
617 | if (lock->type != LCK_SPIN_TYPE) { | |
5ba3f43e | 618 | panic("Invalid spinlock type %p", lock); |
0a7de745 A |
619 | } |
620 | #endif // DEVELOPMENT || DEBUG | |
5ba3f43e A |
621 | hw_lock_unlock(&lock->hwlock); |
622 | } | |
623 | ||
d9a64523 A |
624 | /* |
625 | * Routine: lck_spin_unlock_nopreempt | |
626 | */ | |
627 | void | |
628 | lck_spin_unlock_nopreempt(lck_spin_t *lock) | |
629 | { | |
0a7de745 A |
630 | #if DEVELOPMENT || DEBUG |
631 | if ((LCK_MTX_STATE_TO_THREAD(lock->lck_spin_data) != current_thread()) && LOCK_CORRECTNESS_PANIC()) { | |
d9a64523 | 632 | panic("Spinlock not owned by thread %p = %lx", lock, lock->lck_spin_data); |
0a7de745 A |
633 | } |
634 | if (lock->type != LCK_SPIN_TYPE) { | |
d9a64523 | 635 | panic("Invalid spinlock type %p", lock); |
0a7de745 A |
636 | } |
637 | #endif // DEVELOPMENT || DEBUG | |
d9a64523 A |
638 | hw_lock_unlock_nopreempt(&lock->hwlock); |
639 | } | |
640 | ||
5ba3f43e A |
641 | /* |
642 | * Routine: lck_spin_destroy | |
643 | */ | |
644 | void | |
645 | lck_spin_destroy( | |
0a7de745 A |
646 | lck_spin_t * lck, |
647 | lck_grp_t * grp) | |
5ba3f43e | 648 | { |
0a7de745 | 649 | if (lck->lck_spin_data == LCK_SPIN_TAG_DESTROYED) { |
5ba3f43e | 650 | return; |
0a7de745 | 651 | } |
5ba3f43e | 652 | lck->lck_spin_data = LCK_SPIN_TAG_DESTROYED; |
cb323159 A |
653 | if (grp) { |
654 | lck_grp_lckcnt_decr(grp, LCK_TYPE_SPIN); | |
655 | lck_grp_deallocate(grp); | |
656 | } | |
5ba3f43e A |
657 | } |
658 | ||
659 | /* | |
660 | * Routine: kdp_lck_spin_is_acquired | |
661 | * NOT SAFE: To be used only by kernel debugger to avoid deadlock. | |
662 | */ | |
663 | boolean_t | |
0a7de745 A |
664 | kdp_lck_spin_is_acquired(lck_spin_t *lck) |
665 | { | |
5ba3f43e A |
666 | if (not_in_kdp) { |
667 | panic("panic: spinlock acquired check done outside of kernel debugger"); | |
668 | } | |
669 | return ((lck->lck_spin_data & ~LCK_SPIN_TAG_DESTROYED) != 0) ? TRUE:FALSE; | |
670 | } | |
671 | ||
672 | /* | |
673 | * Initialize a usimple_lock. | |
674 | * | |
675 | * No change in preemption state. | |
676 | */ | |
677 | void | |
678 | usimple_lock_init( | |
0a7de745 A |
679 | usimple_lock_t l, |
680 | unsigned short tag) | |
5ba3f43e | 681 | { |
5ba3f43e | 682 | simple_lock_init((simple_lock_t) l, tag); |
5ba3f43e A |
683 | } |
684 | ||
685 | ||
686 | /* | |
687 | * Acquire a usimple_lock. | |
688 | * | |
689 | * Returns with preemption disabled. Note | |
690 | * that the hw_lock routines are responsible for | |
691 | * maintaining preemption state. | |
692 | */ | |
693 | void | |
0a7de745 A |
694 | (usimple_lock)( |
695 | usimple_lock_t l | |
696 | LCK_GRP_ARG(lck_grp_t *grp)) | |
5ba3f43e | 697 | { |
0a7de745 | 698 | simple_lock((simple_lock_t) l, LCK_GRP_PROBEARG(grp)); |
5ba3f43e A |
699 | } |
700 | ||
701 | ||
702 | extern void sync(void); | |
703 | ||
704 | /* | |
705 | * Release a usimple_lock. | |
706 | * | |
707 | * Returns with preemption enabled. Note | |
708 | * that the hw_lock routines are responsible for | |
709 | * maintaining preemption state. | |
710 | */ | |
711 | void | |
0a7de745 A |
712 | (usimple_unlock)( |
713 | usimple_lock_t l) | |
5ba3f43e | 714 | { |
0a7de745 | 715 | simple_unlock((simple_lock_t)l); |
5ba3f43e A |
716 | } |
717 | ||
718 | ||
719 | /* | |
720 | * Conditionally acquire a usimple_lock. | |
721 | * | |
722 | * On success, returns with preemption disabled. | |
723 | * On failure, returns with preemption in the same state | |
724 | * as when first invoked. Note that the hw_lock routines | |
725 | * are responsible for maintaining preemption state. | |
726 | * | |
727 | * XXX No stats are gathered on a miss; I preserved this | |
728 | * behavior from the original assembly-language code, but | |
729 | * doesn't it make sense to log misses? XXX | |
730 | */ | |
0a7de745 A |
731 | unsigned |
732 | int | |
733 | (usimple_lock_try)( | |
734 | usimple_lock_t l | |
735 | LCK_GRP_ARG(lck_grp_t *grp)) | |
5ba3f43e | 736 | { |
0a7de745 | 737 | return simple_lock_try((simple_lock_t) l, grp); |
5ba3f43e A |
738 | } |
739 | ||
5ba3f43e A |
740 | /* |
741 | * The C portion of the shared/exclusive locks package. | |
742 | */ | |
743 | ||
744 | /* | |
745 | * compute the deadline to spin against when | |
746 | * waiting for a change of state on a lck_rw_t | |
747 | */ | |
5ba3f43e A |
748 | static inline uint64_t |
749 | lck_rw_deadline_for_spin(lck_rw_t *lck) | |
750 | { | |
0a7de745 | 751 | lck_rw_word_t word; |
5ba3f43e A |
752 | |
753 | word.data = ordered_load_rw(lck); | |
754 | if (word.can_sleep) { | |
755 | if (word.r_waiting || word.w_waiting || (word.shared_count > machine_info.max_cpus)) { | |
756 | /* | |
757 | * there are already threads waiting on this lock... this | |
758 | * implies that they have spun beyond their deadlines waiting for | |
759 | * the desired state to show up so we will not bother spinning at this time... | |
760 | * or | |
761 | * the current number of threads sharing this lock exceeds our capacity to run them | |
762 | * concurrently and since all states we're going to spin for require the rw_shared_count | |
763 | * to be at 0, we'll not bother spinning since the latency for this to happen is | |
764 | * unpredictable... | |
765 | */ | |
0a7de745 | 766 | return mach_absolute_time(); |
5ba3f43e | 767 | } |
0a7de745 A |
768 | return mach_absolute_time() + MutexSpin; |
769 | } else { | |
770 | return mach_absolute_time() + (100000LL * 1000000000LL); | |
771 | } | |
5ba3f43e | 772 | } |
5ba3f43e A |
773 | |
774 | static boolean_t | |
775 | lck_rw_drain_status(lck_rw_t *lock, uint32_t status_mask, boolean_t wait __unused) | |
776 | { | |
0a7de745 A |
777 | uint64_t deadline = 0; |
778 | uint32_t data; | |
5ba3f43e | 779 | |
0a7de745 | 780 | if (wait) { |
5ba3f43e | 781 | deadline = lck_rw_deadline_for_spin(lock); |
0a7de745 | 782 | } |
5ba3f43e | 783 | |
0a7de745 | 784 | for (;;) { |
5ba3f43e | 785 | data = load_exclusive32(&lock->lck_rw_data, memory_order_acquire_smp); |
0a7de745 | 786 | if ((data & status_mask) == 0) { |
5ba3f43e | 787 | break; |
0a7de745 A |
788 | } |
789 | if (wait) { | |
5ba3f43e | 790 | wait_for_event(); |
0a7de745 | 791 | } else { |
cb323159 | 792 | os_atomic_clear_exclusive(); |
0a7de745 A |
793 | } |
794 | if (!wait || (mach_absolute_time() >= deadline)) { | |
5ba3f43e | 795 | return FALSE; |
0a7de745 | 796 | } |
5ba3f43e | 797 | } |
cb323159 | 798 | os_atomic_clear_exclusive(); |
5ba3f43e | 799 | return TRUE; |
5ba3f43e A |
800 | } |
801 | ||
802 | /* | |
803 | * Spin while interlock is held. | |
804 | */ | |
805 | static inline void | |
806 | lck_rw_interlock_spin(lck_rw_t *lock) | |
807 | { | |
0a7de745 | 808 | uint32_t data; |
5ba3f43e | 809 | |
0a7de745 | 810 | for (;;) { |
5ba3f43e | 811 | data = load_exclusive32(&lock->lck_rw_data, memory_order_relaxed); |
0a7de745 | 812 | if (data & LCK_RW_INTERLOCK) { |
5ba3f43e | 813 | wait_for_event(); |
0a7de745 | 814 | } else { |
cb323159 | 815 | os_atomic_clear_exclusive(); |
5ba3f43e A |
816 | return; |
817 | } | |
818 | } | |
5ba3f43e A |
819 | } |
820 | ||
821 | /* | |
822 | * We disable interrupts while holding the RW interlock to prevent an | |
823 | * interrupt from exacerbating hold time. | |
824 | * Hence, local helper functions lck_interlock_lock()/lck_interlock_unlock(). | |
825 | */ | |
826 | static inline boolean_t | |
827 | lck_interlock_lock(lck_rw_t *lck) | |
828 | { | |
0a7de745 | 829 | boolean_t istate; |
5ba3f43e | 830 | |
0a7de745 | 831 | istate = ml_set_interrupts_enabled(FALSE); |
5ba3f43e A |
832 | lck_rw_ilk_lock(lck); |
833 | return istate; | |
834 | } | |
835 | ||
836 | static inline void | |
837 | lck_interlock_unlock(lck_rw_t *lck, boolean_t istate) | |
838 | { | |
839 | lck_rw_ilk_unlock(lck); | |
840 | ml_set_interrupts_enabled(istate); | |
841 | } | |
842 | ||
843 | ||
0a7de745 A |
844 | #define LCK_RW_GRAB_WANT 0 |
845 | #define LCK_RW_GRAB_SHARED 1 | |
5ba3f43e A |
846 | |
847 | static boolean_t | |
848 | lck_rw_grab(lck_rw_t *lock, int mode, boolean_t wait) | |
849 | { | |
0a7de745 A |
850 | uint64_t deadline = 0; |
851 | uint32_t data, prev; | |
852 | boolean_t do_exch; | |
5ba3f43e | 853 | |
0a7de745 | 854 | if (wait) { |
5ba3f43e | 855 | deadline = lck_rw_deadline_for_spin(lock); |
0a7de745 | 856 | } |
5ba3f43e | 857 | |
0a7de745 | 858 | for (;;) { |
5ba3f43e A |
859 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_acquire_smp); |
860 | if (data & LCK_RW_INTERLOCK) { | |
861 | atomic_exchange_abort(); | |
862 | lck_rw_interlock_spin(lock); | |
863 | continue; | |
864 | } | |
865 | do_exch = FALSE; | |
866 | if (mode == LCK_RW_GRAB_WANT) { | |
867 | if ((data & LCK_RW_WANT_EXCL) == 0) { | |
868 | data |= LCK_RW_WANT_EXCL; | |
869 | do_exch = TRUE; | |
870 | } | |
0a7de745 | 871 | } else { // LCK_RW_GRAB_SHARED |
5ba3f43e | 872 | if (((data & (LCK_RW_WANT_EXCL | LCK_RW_WANT_UPGRADE)) == 0) || |
0a7de745 | 873 | (((data & LCK_RW_SHARED_MASK)) && ((data & LCK_RW_PRIV_EXCL) == 0))) { |
5ba3f43e A |
874 | data += LCK_RW_SHARED_READER; |
875 | do_exch = TRUE; | |
876 | } | |
877 | } | |
878 | if (do_exch) { | |
0a7de745 | 879 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_acquire_smp)) { |
5ba3f43e | 880 | return TRUE; |
0a7de745 | 881 | } |
5ba3f43e | 882 | } else { |
0a7de745 | 883 | if (wait) { // Non-waiting |
5ba3f43e | 884 | wait_for_event(); |
0a7de745 | 885 | } else { |
5ba3f43e | 886 | atomic_exchange_abort(); |
0a7de745 A |
887 | } |
888 | if (!wait || (mach_absolute_time() >= deadline)) { | |
5ba3f43e | 889 | return FALSE; |
0a7de745 | 890 | } |
5ba3f43e A |
891 | } |
892 | } | |
893 | } | |
894 | ||
895 | ||
896 | /* | |
897 | * Routine: lck_rw_alloc_init | |
898 | */ | |
899 | lck_rw_t * | |
900 | lck_rw_alloc_init( | |
0a7de745 A |
901 | lck_grp_t *grp, |
902 | lck_attr_t *attr) | |
5ba3f43e | 903 | { |
f427ee49 | 904 | lck_rw_t *lck; |
5ba3f43e | 905 | |
f427ee49 A |
906 | lck = zalloc_flags(ZV_LCK_RW, Z_WAITOK | Z_ZERO); |
907 | lck_rw_init(lck, grp, attr); | |
5ba3f43e A |
908 | return lck; |
909 | } | |
910 | ||
911 | /* | |
912 | * Routine: lck_rw_free | |
913 | */ | |
914 | void | |
915 | lck_rw_free( | |
0a7de745 A |
916 | lck_rw_t *lck, |
917 | lck_grp_t *grp) | |
5ba3f43e A |
918 | { |
919 | lck_rw_destroy(lck, grp); | |
f427ee49 | 920 | zfree(ZV_LCK_RW, lck); |
5ba3f43e A |
921 | } |
922 | ||
923 | /* | |
924 | * Routine: lck_rw_init | |
925 | */ | |
926 | void | |
927 | lck_rw_init( | |
0a7de745 A |
928 | lck_rw_t *lck, |
929 | lck_grp_t *grp, | |
930 | lck_attr_t *attr) | |
5ba3f43e | 931 | { |
0a7de745 | 932 | if (attr == LCK_ATTR_NULL) { |
5ba3f43e | 933 | attr = &LockDefaultLckAttr; |
0a7de745 | 934 | } |
5ba3f43e A |
935 | memset(lck, 0, sizeof(lck_rw_t)); |
936 | lck->lck_rw_can_sleep = TRUE; | |
0a7de745 | 937 | if ((attr->lck_attr_val & LCK_ATTR_RW_SHARED_PRIORITY) == 0) { |
5ba3f43e | 938 | lck->lck_rw_priv_excl = TRUE; |
0a7de745 | 939 | } |
5ba3f43e A |
940 | |
941 | lck_grp_reference(grp); | |
942 | lck_grp_lckcnt_incr(grp, LCK_TYPE_RW); | |
943 | } | |
944 | ||
945 | ||
946 | /* | |
947 | * Routine: lck_rw_destroy | |
948 | */ | |
949 | void | |
950 | lck_rw_destroy( | |
0a7de745 A |
951 | lck_rw_t *lck, |
952 | lck_grp_t *grp) | |
5ba3f43e | 953 | { |
0a7de745 | 954 | if (lck->lck_rw_tag == LCK_RW_TAG_DESTROYED) { |
5ba3f43e | 955 | return; |
0a7de745 | 956 | } |
5ba3f43e A |
957 | #if MACH_LDEBUG |
958 | lck_rw_assert(lck, LCK_RW_ASSERT_NOTHELD); | |
959 | #endif | |
960 | lck->lck_rw_tag = LCK_RW_TAG_DESTROYED; | |
961 | lck_grp_lckcnt_decr(grp, LCK_TYPE_RW); | |
962 | lck_grp_deallocate(grp); | |
963 | return; | |
964 | } | |
965 | ||
966 | /* | |
967 | * Routine: lck_rw_lock | |
968 | */ | |
969 | void | |
970 | lck_rw_lock( | |
0a7de745 A |
971 | lck_rw_t *lck, |
972 | lck_rw_type_t lck_rw_type) | |
5ba3f43e | 973 | { |
0a7de745 | 974 | if (lck_rw_type == LCK_RW_TYPE_SHARED) { |
5ba3f43e | 975 | lck_rw_lock_shared(lck); |
0a7de745 | 976 | } else if (lck_rw_type == LCK_RW_TYPE_EXCLUSIVE) { |
5ba3f43e | 977 | lck_rw_lock_exclusive(lck); |
0a7de745 | 978 | } else { |
5ba3f43e | 979 | panic("lck_rw_lock(): Invalid RW lock type: %x", lck_rw_type); |
0a7de745 | 980 | } |
5ba3f43e A |
981 | } |
982 | ||
f427ee49 A |
983 | #define LCK_RW_LOCK_EXCLUSIVE_TAS(lck) (atomic_test_and_set32(&(lck)->lck_rw_data, \ |
984 | (LCK_RW_SHARED_MASK | LCK_RW_WANT_EXCL | LCK_RW_WANT_UPGRADE | LCK_RW_INTERLOCK), \ | |
985 | LCK_RW_WANT_EXCL, memory_order_acquire_smp, FALSE)) | |
986 | ||
987 | /* | |
988 | * Routine: lck_rw_lock_exclusive_check_contended | |
989 | */ | |
990 | bool | |
991 | lck_rw_lock_exclusive_check_contended(lck_rw_t *lock) | |
992 | { | |
993 | thread_t thread = current_thread(); | |
994 | bool contended = false; | |
995 | ||
996 | if (lock->lck_rw_can_sleep) { | |
997 | thread->rwlock_count++; | |
998 | } else if (get_preemption_level() == 0) { | |
999 | panic("Taking non-sleepable RW lock with preemption enabled"); | |
1000 | } | |
1001 | if (LCK_RW_LOCK_EXCLUSIVE_TAS(lock)) { | |
1002 | #if CONFIG_DTRACE | |
1003 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_ACQUIRE, lock, DTRACE_RW_EXCL); | |
1004 | #endif /* CONFIG_DTRACE */ | |
1005 | } else { | |
1006 | contended = true; | |
1007 | lck_rw_lock_exclusive_gen(lock); | |
1008 | } | |
1009 | #if MACH_ASSERT | |
1010 | thread_t owner = ordered_load_rw_owner(lock); | |
1011 | assertf(owner == THREAD_NULL, "state=0x%x, owner=%p", ordered_load_rw(lock), owner); | |
1012 | #endif | |
1013 | ordered_store_rw_owner(lock, thread); | |
1014 | return contended; | |
1015 | } | |
1016 | ||
5ba3f43e A |
1017 | /* |
1018 | * Routine: lck_rw_lock_exclusive | |
1019 | */ | |
1020 | void | |
1021 | lck_rw_lock_exclusive(lck_rw_t *lock) | |
1022 | { | |
0a7de745 | 1023 | thread_t thread = current_thread(); |
5ba3f43e | 1024 | |
f427ee49 A |
1025 | if (lock->lck_rw_can_sleep) { |
1026 | thread->rwlock_count++; | |
1027 | } else if (get_preemption_level() == 0) { | |
1028 | panic("Taking non-sleepable RW lock with preemption enabled"); | |
1029 | } | |
1030 | if (LCK_RW_LOCK_EXCLUSIVE_TAS(lock)) { | |
0a7de745 | 1031 | #if CONFIG_DTRACE |
5ba3f43e | 1032 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_ACQUIRE, lock, DTRACE_RW_EXCL); |
0a7de745 A |
1033 | #endif /* CONFIG_DTRACE */ |
1034 | } else { | |
5ba3f43e | 1035 | lck_rw_lock_exclusive_gen(lock); |
0a7de745 | 1036 | } |
5ba3f43e A |
1037 | #if MACH_ASSERT |
1038 | thread_t owner = ordered_load_rw_owner(lock); | |
1039 | assertf(owner == THREAD_NULL, "state=0x%x, owner=%p", ordered_load_rw(lock), owner); | |
1040 | #endif | |
1041 | ordered_store_rw_owner(lock, thread); | |
1042 | } | |
1043 | ||
1044 | /* | |
1045 | * Routine: lck_rw_lock_shared | |
1046 | */ | |
1047 | void | |
1048 | lck_rw_lock_shared(lck_rw_t *lock) | |
1049 | { | |
0a7de745 | 1050 | uint32_t data, prev; |
5ba3f43e | 1051 | |
f427ee49 A |
1052 | if (lock->lck_rw_can_sleep) { |
1053 | current_thread()->rwlock_count++; | |
1054 | } else if (get_preemption_level() == 0) { | |
1055 | panic("Taking non-sleepable RW lock with preemption enabled"); | |
1056 | } | |
0a7de745 | 1057 | for (;;) { |
5ba3f43e A |
1058 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_acquire_smp); |
1059 | if (data & (LCK_RW_WANT_EXCL | LCK_RW_WANT_UPGRADE | LCK_RW_INTERLOCK)) { | |
1060 | atomic_exchange_abort(); | |
1061 | lck_rw_lock_shared_gen(lock); | |
1062 | break; | |
1063 | } | |
1064 | data += LCK_RW_SHARED_READER; | |
0a7de745 | 1065 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_acquire_smp)) { |
5ba3f43e | 1066 | break; |
0a7de745 | 1067 | } |
5ba3f43e A |
1068 | cpu_pause(); |
1069 | } | |
1070 | #if MACH_ASSERT | |
1071 | thread_t owner = ordered_load_rw_owner(lock); | |
1072 | assertf(owner == THREAD_NULL, "state=0x%x, owner=%p", ordered_load_rw(lock), owner); | |
1073 | #endif | |
0a7de745 | 1074 | #if CONFIG_DTRACE |
5ba3f43e | 1075 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_ACQUIRE, lock, DTRACE_RW_SHARED); |
0a7de745 | 1076 | #endif /* CONFIG_DTRACE */ |
5ba3f43e A |
1077 | return; |
1078 | } | |
1079 | ||
1080 | /* | |
1081 | * Routine: lck_rw_lock_shared_to_exclusive | |
cb323159 A |
1082 | * |
1083 | * False returned upon failure, in this case the shared lock is dropped. | |
5ba3f43e A |
1084 | */ |
1085 | boolean_t | |
1086 | lck_rw_lock_shared_to_exclusive(lck_rw_t *lock) | |
1087 | { | |
0a7de745 | 1088 | uint32_t data, prev; |
5ba3f43e | 1089 | |
0a7de745 | 1090 | for (;;) { |
5ba3f43e A |
1091 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_acquire_smp); |
1092 | if (data & LCK_RW_INTERLOCK) { | |
1093 | atomic_exchange_abort(); | |
1094 | lck_rw_interlock_spin(lock); | |
1095 | continue; | |
1096 | } | |
1097 | if (data & LCK_RW_WANT_UPGRADE) { | |
1098 | data -= LCK_RW_SHARED_READER; | |
0a7de745 A |
1099 | if ((data & LCK_RW_SHARED_MASK) == 0) { /* we were the last reader */ |
1100 | data &= ~(LCK_RW_W_WAITING); /* so clear the wait indicator */ | |
1101 | } | |
1102 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_acquire_smp)) { | |
5ba3f43e | 1103 | return lck_rw_lock_shared_to_exclusive_failure(lock, prev); |
0a7de745 | 1104 | } |
5ba3f43e | 1105 | } else { |
0a7de745 A |
1106 | data |= LCK_RW_WANT_UPGRADE; /* ask for WANT_UPGRADE */ |
1107 | data -= LCK_RW_SHARED_READER; /* and shed our read count */ | |
1108 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_acquire_smp)) { | |
5ba3f43e | 1109 | break; |
0a7de745 | 1110 | } |
5ba3f43e A |
1111 | } |
1112 | cpu_pause(); | |
1113 | } | |
0a7de745 A |
1114 | /* we now own the WANT_UPGRADE */ |
1115 | if (data & LCK_RW_SHARED_MASK) { /* check to see if all of the readers are drained */ | |
1116 | lck_rw_lock_shared_to_exclusive_success(lock); /* if not, we need to go wait */ | |
1117 | } | |
5ba3f43e A |
1118 | #if MACH_ASSERT |
1119 | thread_t owner = ordered_load_rw_owner(lock); | |
1120 | assertf(owner == THREAD_NULL, "state=0x%x, owner=%p", ordered_load_rw(lock), owner); | |
1121 | #endif | |
1122 | ordered_store_rw_owner(lock, current_thread()); | |
0a7de745 | 1123 | #if CONFIG_DTRACE |
5ba3f43e | 1124 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_TO_EXCL_UPGRADE, lock, 0); |
0a7de745 | 1125 | #endif /* CONFIG_DTRACE */ |
5ba3f43e A |
1126 | return TRUE; |
1127 | } | |
1128 | ||
1129 | ||
1130 | /* | |
1131 | * Routine: lck_rw_lock_shared_to_exclusive_failure | |
1132 | * Function: | |
1133 | * Fast path code has already dropped our read | |
1134 | * count and determined that someone else owns 'lck_rw_want_upgrade' | |
1135 | * if 'lck_rw_shared_count' == 0, its also already dropped 'lck_w_waiting' | |
1136 | * all we need to do here is determine if a wakeup is needed | |
1137 | */ | |
1138 | static boolean_t | |
1139 | lck_rw_lock_shared_to_exclusive_failure( | |
0a7de745 A |
1140 | lck_rw_t *lck, |
1141 | uint32_t prior_lock_state) | |
5ba3f43e | 1142 | { |
0a7de745 A |
1143 | thread_t thread = current_thread(); |
1144 | uint32_t rwlock_count; | |
5ba3f43e A |
1145 | |
1146 | /* Check if dropping the lock means that we need to unpromote */ | |
f427ee49 A |
1147 | if (lck->lck_rw_can_sleep) { |
1148 | rwlock_count = thread->rwlock_count--; | |
1149 | } else { | |
1150 | rwlock_count = UINT32_MAX; | |
1151 | } | |
5ba3f43e A |
1152 | #if MACH_LDEBUG |
1153 | if (rwlock_count == 0) { | |
1154 | panic("rw lock count underflow for thread %p", thread); | |
1155 | } | |
1156 | #endif | |
1157 | if ((prior_lock_state & LCK_RW_W_WAITING) && | |
0a7de745 | 1158 | ((prior_lock_state & LCK_RW_SHARED_MASK) == LCK_RW_SHARED_READER)) { |
5ba3f43e A |
1159 | /* |
1160 | * Someone else has requested upgrade. | |
1161 | * Since we've released the read lock, wake | |
1162 | * him up if he's blocked waiting | |
1163 | */ | |
1164 | thread_wakeup(LCK_RW_WRITER_EVENT(lck)); | |
1165 | } | |
1166 | ||
1167 | if ((rwlock_count == 1 /* field now 0 */) && (thread->sched_flags & TH_SFLAG_RW_PROMOTED)) { | |
1168 | /* sched_flags checked without lock, but will be rechecked while clearing */ | |
d9a64523 | 1169 | lck_rw_clear_promotion(thread, unslide_for_kdebug(lck)); |
5ba3f43e A |
1170 | } |
1171 | ||
1172 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_CODE) | DBG_FUNC_NONE, | |
0a7de745 | 1173 | VM_KERNEL_UNSLIDE_OR_PERM(lck), lck->lck_rw_shared_count, lck->lck_rw_want_upgrade, 0, 0); |
5ba3f43e | 1174 | |
0a7de745 | 1175 | return FALSE; |
5ba3f43e A |
1176 | } |
1177 | ||
1178 | /* | |
1179 | * Routine: lck_rw_lock_shared_to_exclusive_success | |
1180 | * Function: | |
1181 | * assembly fast path code has already dropped our read | |
1182 | * count and successfully acquired 'lck_rw_want_upgrade' | |
1183 | * we just need to wait for the rest of the readers to drain | |
1184 | * and then we can return as the exclusive holder of this lock | |
1185 | */ | |
1186 | static boolean_t | |
1187 | lck_rw_lock_shared_to_exclusive_success( | |
0a7de745 A |
1188 | lck_rw_t *lock) |
1189 | { | |
1190 | __kdebug_only uintptr_t trace_lck = VM_KERNEL_UNSLIDE_OR_PERM(lock); | |
1191 | int slept = 0; | |
1192 | lck_rw_word_t word; | |
1193 | wait_result_t res; | |
1194 | boolean_t istate; | |
1195 | boolean_t not_shared; | |
1196 | ||
1197 | #if CONFIG_DTRACE | |
1198 | uint64_t wait_interval = 0; | |
1199 | int readers_at_sleep = 0; | |
1200 | boolean_t dtrace_ls_initialized = FALSE; | |
1201 | boolean_t dtrace_rwl_shared_to_excl_spin, dtrace_rwl_shared_to_excl_block, dtrace_ls_enabled = FALSE; | |
5ba3f43e A |
1202 | #endif |
1203 | ||
1204 | while (!lck_rw_drain_status(lock, LCK_RW_SHARED_MASK, FALSE)) { | |
5ba3f43e | 1205 | word.data = ordered_load_rw(lock); |
0a7de745 | 1206 | #if CONFIG_DTRACE |
5ba3f43e A |
1207 | if (dtrace_ls_initialized == FALSE) { |
1208 | dtrace_ls_initialized = TRUE; | |
1209 | dtrace_rwl_shared_to_excl_spin = (lockstat_probemap[LS_LCK_RW_LOCK_SHARED_TO_EXCL_SPIN] != 0); | |
1210 | dtrace_rwl_shared_to_excl_block = (lockstat_probemap[LS_LCK_RW_LOCK_SHARED_TO_EXCL_BLOCK] != 0); | |
1211 | dtrace_ls_enabled = dtrace_rwl_shared_to_excl_spin || dtrace_rwl_shared_to_excl_block; | |
1212 | if (dtrace_ls_enabled) { | |
1213 | /* | |
1214 | * Either sleeping or spinning is happening, | |
1215 | * start a timing of our delay interval now. | |
1216 | */ | |
1217 | readers_at_sleep = word.shared_count; | |
1218 | wait_interval = mach_absolute_time(); | |
1219 | } | |
1220 | } | |
1221 | #endif | |
1222 | ||
1223 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_SPIN_CODE) | DBG_FUNC_START, | |
0a7de745 | 1224 | trace_lck, word.shared_count, 0, 0, 0); |
5ba3f43e A |
1225 | |
1226 | not_shared = lck_rw_drain_status(lock, LCK_RW_SHARED_MASK, TRUE); | |
1227 | ||
1228 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_SPIN_CODE) | DBG_FUNC_END, | |
0a7de745 | 1229 | trace_lck, lock->lck_rw_shared_count, 0, 0, 0); |
5ba3f43e | 1230 | |
0a7de745 | 1231 | if (not_shared) { |
5ba3f43e | 1232 | break; |
0a7de745 | 1233 | } |
5ba3f43e A |
1234 | |
1235 | /* | |
1236 | * if we get here, the spin deadline in lck_rw_wait_on_status() | |
1237 | * has expired w/o the rw_shared_count having drained to 0 | |
1238 | * check to see if we're allowed to do a thread_block | |
1239 | */ | |
1240 | if (word.can_sleep) { | |
5ba3f43e | 1241 | istate = lck_interlock_lock(lock); |
0a7de745 | 1242 | |
5ba3f43e A |
1243 | word.data = ordered_load_rw(lock); |
1244 | if (word.shared_count != 0) { | |
1245 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_WAIT_CODE) | DBG_FUNC_START, | |
0a7de745 | 1246 | trace_lck, word.shared_count, 0, 0, 0); |
5ba3f43e A |
1247 | |
1248 | word.w_waiting = 1; | |
1249 | ordered_store_rw(lock, word.data); | |
1250 | ||
1251 | thread_set_pending_block_hint(current_thread(), kThreadWaitKernelRWLockUpgrade); | |
d9a64523 | 1252 | res = assert_wait(LCK_RW_WRITER_EVENT(lock), |
0a7de745 | 1253 | THREAD_UNINT | THREAD_WAIT_NOREPORT_USER); |
5ba3f43e A |
1254 | lck_interlock_unlock(lock, istate); |
1255 | ||
1256 | if (res == THREAD_WAITING) { | |
1257 | res = thread_block(THREAD_CONTINUE_NULL); | |
1258 | slept++; | |
1259 | } | |
1260 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_WAIT_CODE) | DBG_FUNC_END, | |
0a7de745 | 1261 | trace_lck, res, slept, 0, 0); |
5ba3f43e A |
1262 | } else { |
1263 | lck_interlock_unlock(lock, istate); | |
1264 | break; | |
1265 | } | |
1266 | } | |
1267 | } | |
0a7de745 | 1268 | #if CONFIG_DTRACE |
5ba3f43e A |
1269 | /* |
1270 | * We infer whether we took the sleep/spin path above by checking readers_at_sleep. | |
1271 | */ | |
1272 | if (dtrace_ls_enabled == TRUE) { | |
1273 | if (slept == 0) { | |
0a7de745 | 1274 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_TO_EXCL_SPIN, lock, mach_absolute_time() - wait_interval, 0); |
5ba3f43e | 1275 | } else { |
0a7de745 | 1276 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_TO_EXCL_BLOCK, lock, |
5ba3f43e A |
1277 | mach_absolute_time() - wait_interval, 1, |
1278 | (readers_at_sleep == 0 ? 1 : 0), readers_at_sleep); | |
1279 | } | |
1280 | } | |
1281 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_TO_EXCL_UPGRADE, lock, 1); | |
1282 | #endif | |
0a7de745 | 1283 | return TRUE; |
5ba3f43e A |
1284 | } |
1285 | ||
1286 | ||
1287 | /* | |
1288 | * Routine: lck_rw_lock_exclusive_to_shared | |
1289 | */ | |
1290 | ||
0a7de745 A |
1291 | void |
1292 | lck_rw_lock_exclusive_to_shared(lck_rw_t *lock) | |
5ba3f43e | 1293 | { |
0a7de745 | 1294 | uint32_t data, prev; |
5ba3f43e A |
1295 | |
1296 | assertf(lock->lck_rw_owner == current_thread(), "state=0x%x, owner=%p", lock->lck_rw_data, lock->lck_rw_owner); | |
1297 | ordered_store_rw_owner(lock, THREAD_NULL); | |
0a7de745 | 1298 | for (;;) { |
5ba3f43e A |
1299 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_release_smp); |
1300 | if (data & LCK_RW_INTERLOCK) { | |
5ba3f43e | 1301 | atomic_exchange_abort(); |
0a7de745 | 1302 | lck_rw_interlock_spin(lock); /* wait for interlock to clear */ |
5ba3f43e | 1303 | continue; |
5ba3f43e A |
1304 | } |
1305 | data += LCK_RW_SHARED_READER; | |
0a7de745 | 1306 | if (data & LCK_RW_WANT_UPGRADE) { |
5ba3f43e | 1307 | data &= ~(LCK_RW_WANT_UPGRADE); |
0a7de745 | 1308 | } else { |
5ba3f43e | 1309 | data &= ~(LCK_RW_WANT_EXCL); |
0a7de745 A |
1310 | } |
1311 | if (!((prev & LCK_RW_W_WAITING) && (prev & LCK_RW_PRIV_EXCL))) { | |
5ba3f43e | 1312 | data &= ~(LCK_RW_W_WAITING); |
0a7de745 A |
1313 | } |
1314 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_release_smp)) { | |
5ba3f43e | 1315 | break; |
0a7de745 | 1316 | } |
5ba3f43e A |
1317 | cpu_pause(); |
1318 | } | |
1319 | return lck_rw_lock_exclusive_to_shared_gen(lock, prev); | |
1320 | } | |
1321 | ||
1322 | /* | |
1323 | * Routine: lck_rw_lock_exclusive_to_shared_gen | |
0a7de745 | 1324 | * Function: |
5ba3f43e A |
1325 | * Fast path has already dropped |
1326 | * our exclusive state and bumped lck_rw_shared_count | |
1327 | * all we need to do here is determine if anyone | |
1328 | * needs to be awakened. | |
1329 | */ | |
1330 | static void | |
1331 | lck_rw_lock_exclusive_to_shared_gen( | |
0a7de745 A |
1332 | lck_rw_t *lck, |
1333 | uint32_t prior_lock_state) | |
5ba3f43e | 1334 | { |
0a7de745 A |
1335 | __kdebug_only uintptr_t trace_lck = VM_KERNEL_UNSLIDE_OR_PERM(lck); |
1336 | lck_rw_word_t fake_lck; | |
5ba3f43e A |
1337 | |
1338 | /* | |
1339 | * prior_lock state is a snapshot of the 1st word of the | |
1340 | * lock in question... we'll fake up a pointer to it | |
1341 | * and carefully not access anything beyond whats defined | |
1342 | * in the first word of a lck_rw_t | |
1343 | */ | |
1344 | fake_lck.data = prior_lock_state; | |
1345 | ||
1346 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_TO_SH_CODE) | DBG_FUNC_START, | |
0a7de745 | 1347 | trace_lck, fake_lck->want_excl, fake_lck->want_upgrade, 0, 0); |
5ba3f43e A |
1348 | |
1349 | /* | |
1350 | * don't wake up anyone waiting to take the lock exclusively | |
1351 | * since we hold a read count... when the read count drops to 0, | |
1352 | * the writers will be woken. | |
1353 | * | |
1354 | * wake up any waiting readers if we don't have any writers waiting, | |
1355 | * or the lock is NOT marked as rw_priv_excl (writers have privilege) | |
1356 | */ | |
0a7de745 | 1357 | if (!(fake_lck.priv_excl && fake_lck.w_waiting) && fake_lck.r_waiting) { |
5ba3f43e | 1358 | thread_wakeup(LCK_RW_READER_EVENT(lck)); |
0a7de745 | 1359 | } |
5ba3f43e A |
1360 | |
1361 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_TO_SH_CODE) | DBG_FUNC_END, | |
0a7de745 | 1362 | trace_lck, lck->lck_rw_want_excl, lck->lck_rw_want_upgrade, lck->lck_rw_shared_count, 0); |
5ba3f43e A |
1363 | |
1364 | #if CONFIG_DTRACE | |
1365 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_TO_SHARED_DOWNGRADE, lck, 0); | |
1366 | #endif | |
1367 | } | |
1368 | ||
1369 | ||
1370 | /* | |
1371 | * Routine: lck_rw_try_lock | |
1372 | */ | |
1373 | boolean_t | |
1374 | lck_rw_try_lock( | |
0a7de745 A |
1375 | lck_rw_t *lck, |
1376 | lck_rw_type_t lck_rw_type) | |
5ba3f43e | 1377 | { |
0a7de745 | 1378 | if (lck_rw_type == LCK_RW_TYPE_SHARED) { |
5ba3f43e | 1379 | return lck_rw_try_lock_shared(lck); |
0a7de745 | 1380 | } else if (lck_rw_type == LCK_RW_TYPE_EXCLUSIVE) { |
5ba3f43e | 1381 | return lck_rw_try_lock_exclusive(lck); |
0a7de745 | 1382 | } else { |
5ba3f43e | 1383 | panic("lck_rw_try_lock(): Invalid rw lock type: %x", lck_rw_type); |
0a7de745 | 1384 | } |
5ba3f43e A |
1385 | return FALSE; |
1386 | } | |
1387 | ||
1388 | /* | |
1389 | * Routine: lck_rw_try_lock_shared | |
1390 | */ | |
1391 | ||
0a7de745 A |
1392 | boolean_t |
1393 | lck_rw_try_lock_shared(lck_rw_t *lock) | |
5ba3f43e | 1394 | { |
0a7de745 | 1395 | uint32_t data, prev; |
5ba3f43e | 1396 | |
0a7de745 | 1397 | for (;;) { |
5ba3f43e A |
1398 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_acquire_smp); |
1399 | if (data & LCK_RW_INTERLOCK) { | |
5ba3f43e A |
1400 | atomic_exchange_abort(); |
1401 | lck_rw_interlock_spin(lock); | |
1402 | continue; | |
5ba3f43e A |
1403 | } |
1404 | if (data & (LCK_RW_WANT_EXCL | LCK_RW_WANT_UPGRADE)) { | |
1405 | atomic_exchange_abort(); | |
0a7de745 | 1406 | return FALSE; /* lock is busy */ |
5ba3f43e | 1407 | } |
0a7de745 A |
1408 | data += LCK_RW_SHARED_READER; /* Increment reader refcount */ |
1409 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_acquire_smp)) { | |
5ba3f43e | 1410 | break; |
0a7de745 | 1411 | } |
5ba3f43e A |
1412 | cpu_pause(); |
1413 | } | |
1414 | #if MACH_ASSERT | |
1415 | thread_t owner = ordered_load_rw_owner(lock); | |
1416 | assertf(owner == THREAD_NULL, "state=0x%x, owner=%p", ordered_load_rw(lock), owner); | |
1417 | #endif | |
f427ee49 A |
1418 | |
1419 | if (lock->lck_rw_can_sleep) { | |
1420 | current_thread()->rwlock_count++; | |
1421 | } else if (get_preemption_level() == 0) { | |
1422 | panic("Taking non-sleepable RW lock with preemption enabled"); | |
1423 | } | |
1424 | ||
0a7de745 | 1425 | #if CONFIG_DTRACE |
5ba3f43e | 1426 | LOCKSTAT_RECORD(LS_LCK_RW_TRY_LOCK_SHARED_ACQUIRE, lock, DTRACE_RW_SHARED); |
0a7de745 | 1427 | #endif /* CONFIG_DTRACE */ |
5ba3f43e A |
1428 | return TRUE; |
1429 | } | |
1430 | ||
1431 | ||
1432 | /* | |
1433 | * Routine: lck_rw_try_lock_exclusive | |
1434 | */ | |
1435 | ||
0a7de745 A |
1436 | boolean_t |
1437 | lck_rw_try_lock_exclusive(lck_rw_t *lock) | |
5ba3f43e | 1438 | { |
0a7de745 A |
1439 | uint32_t data, prev; |
1440 | thread_t thread; | |
5ba3f43e | 1441 | |
0a7de745 | 1442 | for (;;) { |
5ba3f43e A |
1443 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_acquire_smp); |
1444 | if (data & LCK_RW_INTERLOCK) { | |
5ba3f43e A |
1445 | atomic_exchange_abort(); |
1446 | lck_rw_interlock_spin(lock); | |
1447 | continue; | |
5ba3f43e A |
1448 | } |
1449 | if (data & (LCK_RW_SHARED_MASK | LCK_RW_WANT_EXCL | LCK_RW_WANT_UPGRADE)) { | |
1450 | atomic_exchange_abort(); | |
1451 | return FALSE; | |
1452 | } | |
1453 | data |= LCK_RW_WANT_EXCL; | |
0a7de745 | 1454 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_acquire_smp)) { |
5ba3f43e | 1455 | break; |
0a7de745 | 1456 | } |
5ba3f43e A |
1457 | cpu_pause(); |
1458 | } | |
1459 | thread = current_thread(); | |
f427ee49 A |
1460 | if (lock->lck_rw_can_sleep) { |
1461 | thread->rwlock_count++; | |
1462 | } else if (get_preemption_level() == 0) { | |
1463 | panic("Taking non-sleepable RW lock with preemption enabled"); | |
1464 | } | |
5ba3f43e A |
1465 | #if MACH_ASSERT |
1466 | thread_t owner = ordered_load_rw_owner(lock); | |
1467 | assertf(owner == THREAD_NULL, "state=0x%x, owner=%p", ordered_load_rw(lock), owner); | |
1468 | #endif | |
1469 | ordered_store_rw_owner(lock, thread); | |
0a7de745 | 1470 | #if CONFIG_DTRACE |
5ba3f43e | 1471 | LOCKSTAT_RECORD(LS_LCK_RW_TRY_LOCK_EXCL_ACQUIRE, lock, DTRACE_RW_EXCL); |
0a7de745 | 1472 | #endif /* CONFIG_DTRACE */ |
5ba3f43e A |
1473 | return TRUE; |
1474 | } | |
1475 | ||
1476 | ||
1477 | /* | |
1478 | * Routine: lck_rw_unlock | |
1479 | */ | |
1480 | void | |
1481 | lck_rw_unlock( | |
0a7de745 A |
1482 | lck_rw_t *lck, |
1483 | lck_rw_type_t lck_rw_type) | |
5ba3f43e | 1484 | { |
0a7de745 | 1485 | if (lck_rw_type == LCK_RW_TYPE_SHARED) { |
5ba3f43e | 1486 | lck_rw_unlock_shared(lck); |
0a7de745 | 1487 | } else if (lck_rw_type == LCK_RW_TYPE_EXCLUSIVE) { |
5ba3f43e | 1488 | lck_rw_unlock_exclusive(lck); |
0a7de745 | 1489 | } else { |
5ba3f43e | 1490 | panic("lck_rw_unlock(): Invalid RW lock type: %d", lck_rw_type); |
0a7de745 | 1491 | } |
5ba3f43e A |
1492 | } |
1493 | ||
1494 | ||
1495 | /* | |
1496 | * Routine: lck_rw_unlock_shared | |
1497 | */ | |
1498 | void | |
1499 | lck_rw_unlock_shared( | |
0a7de745 | 1500 | lck_rw_t *lck) |
5ba3f43e | 1501 | { |
0a7de745 | 1502 | lck_rw_type_t ret; |
5ba3f43e A |
1503 | |
1504 | assertf(lck->lck_rw_owner == THREAD_NULL, "state=0x%x, owner=%p", lck->lck_rw_data, lck->lck_rw_owner); | |
1505 | assertf(lck->lck_rw_shared_count > 0, "shared_count=0x%x", lck->lck_rw_shared_count); | |
1506 | ret = lck_rw_done(lck); | |
1507 | ||
0a7de745 | 1508 | if (ret != LCK_RW_TYPE_SHARED) { |
5ba3f43e | 1509 | panic("lck_rw_unlock_shared(): lock %p held in mode: %d", lck, ret); |
0a7de745 | 1510 | } |
5ba3f43e A |
1511 | } |
1512 | ||
1513 | ||
1514 | /* | |
1515 | * Routine: lck_rw_unlock_exclusive | |
1516 | */ | |
1517 | void | |
1518 | lck_rw_unlock_exclusive( | |
0a7de745 | 1519 | lck_rw_t *lck) |
5ba3f43e | 1520 | { |
0a7de745 | 1521 | lck_rw_type_t ret; |
5ba3f43e A |
1522 | |
1523 | assertf(lck->lck_rw_owner == current_thread(), "state=0x%x, owner=%p", lck->lck_rw_data, lck->lck_rw_owner); | |
1524 | ret = lck_rw_done(lck); | |
1525 | ||
0a7de745 | 1526 | if (ret != LCK_RW_TYPE_EXCLUSIVE) { |
5ba3f43e | 1527 | panic("lck_rw_unlock_exclusive(): lock %p held in mode: %d", lck, ret); |
0a7de745 | 1528 | } |
5ba3f43e A |
1529 | } |
1530 | ||
1531 | ||
1532 | /* | |
1533 | * Routine: lck_rw_lock_exclusive_gen | |
1534 | */ | |
1535 | static void | |
1536 | lck_rw_lock_exclusive_gen( | |
0a7de745 | 1537 | lck_rw_t *lock) |
5ba3f43e | 1538 | { |
0a7de745 A |
1539 | __kdebug_only uintptr_t trace_lck = VM_KERNEL_UNSLIDE_OR_PERM(lock); |
1540 | lck_rw_word_t word; | |
1541 | int slept = 0; | |
1542 | boolean_t gotlock = 0; | |
1543 | boolean_t not_shared_or_upgrade = 0; | |
1544 | wait_result_t res = 0; | |
1545 | boolean_t istate; | |
5ba3f43e | 1546 | |
0a7de745 | 1547 | #if CONFIG_DTRACE |
5ba3f43e | 1548 | boolean_t dtrace_ls_initialized = FALSE; |
0a7de745 | 1549 | boolean_t dtrace_rwl_excl_spin, dtrace_rwl_excl_block, dtrace_ls_enabled = FALSE; |
5ba3f43e A |
1550 | uint64_t wait_interval = 0; |
1551 | int readers_at_sleep = 0; | |
1552 | #endif | |
1553 | ||
1554 | /* | |
1555 | * Try to acquire the lck_rw_want_excl bit. | |
1556 | */ | |
1557 | while (!lck_rw_grab(lock, LCK_RW_GRAB_WANT, FALSE)) { | |
0a7de745 | 1558 | #if CONFIG_DTRACE |
5ba3f43e A |
1559 | if (dtrace_ls_initialized == FALSE) { |
1560 | dtrace_ls_initialized = TRUE; | |
1561 | dtrace_rwl_excl_spin = (lockstat_probemap[LS_LCK_RW_LOCK_EXCL_SPIN] != 0); | |
1562 | dtrace_rwl_excl_block = (lockstat_probemap[LS_LCK_RW_LOCK_EXCL_BLOCK] != 0); | |
1563 | dtrace_ls_enabled = dtrace_rwl_excl_spin || dtrace_rwl_excl_block; | |
1564 | if (dtrace_ls_enabled) { | |
1565 | /* | |
1566 | * Either sleeping or spinning is happening, | |
1567 | * start a timing of our delay interval now. | |
1568 | */ | |
1569 | readers_at_sleep = lock->lck_rw_shared_count; | |
1570 | wait_interval = mach_absolute_time(); | |
1571 | } | |
1572 | } | |
1573 | #endif | |
1574 | ||
1575 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_WRITER_SPIN_CODE) | DBG_FUNC_START, trace_lck, 0, 0, 0, 0); | |
1576 | ||
1577 | gotlock = lck_rw_grab(lock, LCK_RW_GRAB_WANT, TRUE); | |
1578 | ||
1579 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_WRITER_SPIN_CODE) | DBG_FUNC_END, trace_lck, 0, 0, gotlock, 0); | |
1580 | ||
0a7de745 | 1581 | if (gotlock) { |
5ba3f43e | 1582 | break; |
0a7de745 | 1583 | } |
5ba3f43e A |
1584 | /* |
1585 | * if we get here, the deadline has expired w/o us | |
1586 | * being able to grab the lock exclusively | |
1587 | * check to see if we're allowed to do a thread_block | |
1588 | */ | |
1589 | word.data = ordered_load_rw(lock); | |
1590 | if (word.can_sleep) { | |
5ba3f43e A |
1591 | istate = lck_interlock_lock(lock); |
1592 | word.data = ordered_load_rw(lock); | |
1593 | ||
1594 | if (word.want_excl) { | |
5ba3f43e A |
1595 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_WRITER_WAIT_CODE) | DBG_FUNC_START, trace_lck, 0, 0, 0, 0); |
1596 | ||
1597 | word.w_waiting = 1; | |
1598 | ordered_store_rw(lock, word.data); | |
1599 | ||
1600 | thread_set_pending_block_hint(current_thread(), kThreadWaitKernelRWLockWrite); | |
d9a64523 | 1601 | res = assert_wait(LCK_RW_WRITER_EVENT(lock), |
0a7de745 | 1602 | THREAD_UNINT | THREAD_WAIT_NOREPORT_USER); |
5ba3f43e A |
1603 | lck_interlock_unlock(lock, istate); |
1604 | ||
1605 | if (res == THREAD_WAITING) { | |
1606 | res = thread_block(THREAD_CONTINUE_NULL); | |
1607 | slept++; | |
1608 | } | |
1609 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_WRITER_WAIT_CODE) | DBG_FUNC_END, trace_lck, res, slept, 0, 0); | |
1610 | } else { | |
1611 | word.want_excl = 1; | |
1612 | ordered_store_rw(lock, word.data); | |
1613 | lck_interlock_unlock(lock, istate); | |
1614 | break; | |
1615 | } | |
1616 | } | |
1617 | } | |
1618 | /* | |
1619 | * Wait for readers (and upgrades) to finish... | |
1620 | */ | |
1621 | while (!lck_rw_drain_status(lock, LCK_RW_SHARED_MASK | LCK_RW_WANT_UPGRADE, FALSE)) { | |
0a7de745 | 1622 | #if CONFIG_DTRACE |
5ba3f43e A |
1623 | /* |
1624 | * Either sleeping or spinning is happening, start | |
1625 | * a timing of our delay interval now. If we set it | |
1626 | * to -1 we don't have accurate data so we cannot later | |
1627 | * decide to record a dtrace spin or sleep event. | |
1628 | */ | |
1629 | if (dtrace_ls_initialized == FALSE) { | |
1630 | dtrace_ls_initialized = TRUE; | |
1631 | dtrace_rwl_excl_spin = (lockstat_probemap[LS_LCK_RW_LOCK_EXCL_SPIN] != 0); | |
1632 | dtrace_rwl_excl_block = (lockstat_probemap[LS_LCK_RW_LOCK_EXCL_BLOCK] != 0); | |
1633 | dtrace_ls_enabled = dtrace_rwl_excl_spin || dtrace_rwl_excl_block; | |
1634 | if (dtrace_ls_enabled) { | |
1635 | /* | |
1636 | * Either sleeping or spinning is happening, | |
1637 | * start a timing of our delay interval now. | |
1638 | */ | |
1639 | readers_at_sleep = lock->lck_rw_shared_count; | |
1640 | wait_interval = mach_absolute_time(); | |
1641 | } | |
1642 | } | |
1643 | #endif | |
1644 | ||
1645 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_READER_SPIN_CODE) | DBG_FUNC_START, trace_lck, 0, 0, 0, 0); | |
1646 | ||
1647 | not_shared_or_upgrade = lck_rw_drain_status(lock, LCK_RW_SHARED_MASK | LCK_RW_WANT_UPGRADE, TRUE); | |
1648 | ||
1649 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_READER_SPIN_CODE) | DBG_FUNC_END, trace_lck, 0, 0, not_shared_or_upgrade, 0); | |
1650 | ||
0a7de745 | 1651 | if (not_shared_or_upgrade) { |
5ba3f43e | 1652 | break; |
0a7de745 | 1653 | } |
5ba3f43e A |
1654 | /* |
1655 | * if we get here, the deadline has expired w/o us | |
1656 | * being able to grab the lock exclusively | |
1657 | * check to see if we're allowed to do a thread_block | |
1658 | */ | |
1659 | word.data = ordered_load_rw(lock); | |
1660 | if (word.can_sleep) { | |
5ba3f43e A |
1661 | istate = lck_interlock_lock(lock); |
1662 | word.data = ordered_load_rw(lock); | |
1663 | ||
1664 | if (word.shared_count != 0 || word.want_upgrade) { | |
1665 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_READER_WAIT_CODE) | DBG_FUNC_START, trace_lck, 0, 0, 0, 0); | |
1666 | ||
1667 | word.w_waiting = 1; | |
1668 | ordered_store_rw(lock, word.data); | |
1669 | ||
1670 | thread_set_pending_block_hint(current_thread(), kThreadWaitKernelRWLockWrite); | |
d9a64523 | 1671 | res = assert_wait(LCK_RW_WRITER_EVENT(lock), |
0a7de745 | 1672 | THREAD_UNINT | THREAD_WAIT_NOREPORT_USER); |
5ba3f43e A |
1673 | lck_interlock_unlock(lock, istate); |
1674 | ||
1675 | if (res == THREAD_WAITING) { | |
1676 | res = thread_block(THREAD_CONTINUE_NULL); | |
1677 | slept++; | |
1678 | } | |
1679 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EX_READER_WAIT_CODE) | DBG_FUNC_END, trace_lck, res, slept, 0, 0); | |
1680 | } else { | |
1681 | lck_interlock_unlock(lock, istate); | |
1682 | /* | |
1683 | * must own the lock now, since we checked for | |
1684 | * readers or upgrade owner behind the interlock | |
1685 | * no need for a call to 'lck_rw_drain_status' | |
1686 | */ | |
1687 | break; | |
1688 | } | |
1689 | } | |
1690 | } | |
1691 | ||
0a7de745 | 1692 | #if CONFIG_DTRACE |
5ba3f43e A |
1693 | /* |
1694 | * Decide what latencies we suffered that are Dtrace events. | |
1695 | * If we have set wait_interval, then we either spun or slept. | |
1696 | * At least we get out from under the interlock before we record | |
1697 | * which is the best we can do here to minimize the impact | |
1698 | * of the tracing. | |
1699 | * If we have set wait_interval to -1, then dtrace was not enabled when we | |
1700 | * started sleeping/spinning so we don't record this event. | |
1701 | */ | |
1702 | if (dtrace_ls_enabled == TRUE) { | |
1703 | if (slept == 0) { | |
0a7de745 | 1704 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_SPIN, lock, |
5ba3f43e A |
1705 | mach_absolute_time() - wait_interval, 1); |
1706 | } else { | |
1707 | /* | |
1708 | * For the blocking case, we also record if when we blocked | |
1709 | * it was held for read or write, and how many readers. | |
1710 | * Notice that above we recorded this before we dropped | |
1711 | * the interlock so the count is accurate. | |
1712 | */ | |
0a7de745 | 1713 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_BLOCK, lock, |
5ba3f43e A |
1714 | mach_absolute_time() - wait_interval, 1, |
1715 | (readers_at_sleep == 0 ? 1 : 0), readers_at_sleep); | |
1716 | } | |
1717 | } | |
1718 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_ACQUIRE, lock, 1); | |
0a7de745 | 1719 | #endif /* CONFIG_DTRACE */ |
5ba3f43e A |
1720 | } |
1721 | ||
1722 | /* | |
1723 | * Routine: lck_rw_done | |
1724 | */ | |
1725 | ||
0a7de745 A |
1726 | lck_rw_type_t |
1727 | lck_rw_done(lck_rw_t *lock) | |
5ba3f43e | 1728 | { |
0a7de745 A |
1729 | uint32_t data, prev; |
1730 | boolean_t once = FALSE; | |
5ba3f43e | 1731 | |
0a7de745 | 1732 | for (;;) { |
5ba3f43e | 1733 | data = atomic_exchange_begin32(&lock->lck_rw_data, &prev, memory_order_release_smp); |
0a7de745 | 1734 | if (data & LCK_RW_INTERLOCK) { /* wait for interlock to clear */ |
5ba3f43e A |
1735 | atomic_exchange_abort(); |
1736 | lck_rw_interlock_spin(lock); | |
1737 | continue; | |
5ba3f43e | 1738 | } |
0a7de745 | 1739 | if (data & LCK_RW_SHARED_MASK) { /* lock is held shared */ |
5ba3f43e A |
1740 | assertf(lock->lck_rw_owner == THREAD_NULL, "state=0x%x, owner=%p", lock->lck_rw_data, lock->lck_rw_owner); |
1741 | data -= LCK_RW_SHARED_READER; | |
0a7de745 | 1742 | if ((data & LCK_RW_SHARED_MASK) == 0) { /* if reader count has now gone to 0, check for waiters */ |
5ba3f43e | 1743 | goto check_waiters; |
0a7de745 A |
1744 | } |
1745 | } else { /* if reader count == 0, must be exclusive lock */ | |
5ba3f43e A |
1746 | if (data & LCK_RW_WANT_UPGRADE) { |
1747 | data &= ~(LCK_RW_WANT_UPGRADE); | |
1748 | } else { | |
0a7de745 | 1749 | if (data & LCK_RW_WANT_EXCL) { |
5ba3f43e | 1750 | data &= ~(LCK_RW_WANT_EXCL); |
0a7de745 | 1751 | } else { /* lock is not 'owned', panic */ |
5ba3f43e | 1752 | panic("Releasing non-exclusive RW lock without a reader refcount!"); |
0a7de745 | 1753 | } |
5ba3f43e A |
1754 | } |
1755 | if (!once) { | |
1756 | // Only check for holder and clear it once | |
1757 | assertf(lock->lck_rw_owner == current_thread(), "state=0x%x, owner=%p", lock->lck_rw_data, lock->lck_rw_owner); | |
1758 | ordered_store_rw_owner(lock, THREAD_NULL); | |
1759 | once = TRUE; | |
1760 | } | |
1761 | check_waiters: | |
1762 | /* | |
1763 | * test the original values to match what | |
1764 | * lck_rw_done_gen is going to do to determine | |
1765 | * which wakeups need to happen... | |
1766 | * | |
1767 | * if !(fake_lck->lck_rw_priv_excl && fake_lck->lck_w_waiting) | |
1768 | */ | |
1769 | if (prev & LCK_RW_W_WAITING) { | |
1770 | data &= ~(LCK_RW_W_WAITING); | |
0a7de745 | 1771 | if ((prev & LCK_RW_PRIV_EXCL) == 0) { |
5ba3f43e | 1772 | data &= ~(LCK_RW_R_WAITING); |
0a7de745 A |
1773 | } |
1774 | } else { | |
5ba3f43e | 1775 | data &= ~(LCK_RW_R_WAITING); |
0a7de745 | 1776 | } |
5ba3f43e | 1777 | } |
0a7de745 | 1778 | if (atomic_exchange_complete32(&lock->lck_rw_data, prev, data, memory_order_release_smp)) { |
5ba3f43e | 1779 | break; |
0a7de745 | 1780 | } |
5ba3f43e A |
1781 | cpu_pause(); |
1782 | } | |
1783 | return lck_rw_done_gen(lock, prev); | |
1784 | } | |
1785 | ||
1786 | /* | |
1787 | * Routine: lck_rw_done_gen | |
1788 | * | |
1789 | * called from the assembly language wrapper... | |
1790 | * prior_lock_state is the value in the 1st | |
0a7de745 | 1791 | * word of the lock at the time of a successful |
5ba3f43e | 1792 | * atomic compare and exchange with the new value... |
0a7de745 | 1793 | * it represents the state of the lock before we |
5ba3f43e | 1794 | * decremented the rw_shared_count or cleared either |
0a7de745 | 1795 | * rw_want_upgrade or rw_want_write and |
5ba3f43e | 1796 | * the lck_x_waiting bits... since the wrapper |
0a7de745 | 1797 | * routine has already changed the state atomically, |
5ba3f43e A |
1798 | * we just need to decide if we should |
1799 | * wake up anyone and what value to return... we do | |
1800 | * this by examining the state of the lock before | |
1801 | * we changed it | |
1802 | */ | |
1803 | static lck_rw_type_t | |
1804 | lck_rw_done_gen( | |
0a7de745 A |
1805 | lck_rw_t *lck, |
1806 | uint32_t prior_lock_state) | |
5ba3f43e | 1807 | { |
0a7de745 A |
1808 | lck_rw_word_t fake_lck; |
1809 | lck_rw_type_t lock_type; | |
1810 | thread_t thread; | |
1811 | uint32_t rwlock_count; | |
5ba3f43e A |
1812 | |
1813 | /* | |
1814 | * prior_lock state is a snapshot of the 1st word of the | |
1815 | * lock in question... we'll fake up a pointer to it | |
1816 | * and carefully not access anything beyond whats defined | |
1817 | * in the first word of a lck_rw_t | |
1818 | */ | |
1819 | fake_lck.data = prior_lock_state; | |
1820 | ||
1821 | if (fake_lck.shared_count <= 1) { | |
0a7de745 | 1822 | if (fake_lck.w_waiting) { |
5ba3f43e | 1823 | thread_wakeup(LCK_RW_WRITER_EVENT(lck)); |
0a7de745 | 1824 | } |
5ba3f43e | 1825 | |
0a7de745 | 1826 | if (!(fake_lck.priv_excl && fake_lck.w_waiting) && fake_lck.r_waiting) { |
5ba3f43e | 1827 | thread_wakeup(LCK_RW_READER_EVENT(lck)); |
0a7de745 | 1828 | } |
5ba3f43e | 1829 | } |
0a7de745 | 1830 | if (fake_lck.shared_count) { |
5ba3f43e | 1831 | lock_type = LCK_RW_TYPE_SHARED; |
0a7de745 | 1832 | } else { |
5ba3f43e | 1833 | lock_type = LCK_RW_TYPE_EXCLUSIVE; |
0a7de745 | 1834 | } |
5ba3f43e A |
1835 | |
1836 | /* Check if dropping the lock means that we need to unpromote */ | |
1837 | thread = current_thread(); | |
f427ee49 A |
1838 | if (fake_lck.can_sleep) { |
1839 | rwlock_count = thread->rwlock_count--; | |
1840 | } else { | |
1841 | rwlock_count = UINT32_MAX; | |
1842 | } | |
5ba3f43e | 1843 | #if MACH_LDEBUG |
0a7de745 | 1844 | if (rwlock_count == 0) { |
5ba3f43e | 1845 | panic("rw lock count underflow for thread %p", thread); |
0a7de745 | 1846 | } |
5ba3f43e A |
1847 | #endif |
1848 | if ((rwlock_count == 1 /* field now 0 */) && (thread->sched_flags & TH_SFLAG_RW_PROMOTED)) { | |
1849 | /* sched_flags checked without lock, but will be rechecked while clearing */ | |
d9a64523 | 1850 | lck_rw_clear_promotion(thread, unslide_for_kdebug(lck)); |
5ba3f43e A |
1851 | } |
1852 | #if CONFIG_DTRACE | |
1853 | LOCKSTAT_RECORD(LS_LCK_RW_DONE_RELEASE, lck, lock_type == LCK_RW_TYPE_SHARED ? 0 : 1); | |
1854 | #endif | |
1855 | return lock_type; | |
1856 | } | |
1857 | ||
1858 | /* | |
1859 | * Routine: lck_rw_lock_shared_gen | |
1860 | * Function: | |
1861 | * Fast path code has determined that this lock | |
1862 | * is held exclusively... this is where we spin/block | |
1863 | * until we can acquire the lock in the shared mode | |
1864 | */ | |
1865 | static void | |
1866 | lck_rw_lock_shared_gen( | |
0a7de745 | 1867 | lck_rw_t *lck) |
5ba3f43e | 1868 | { |
0a7de745 A |
1869 | __kdebug_only uintptr_t trace_lck = VM_KERNEL_UNSLIDE_OR_PERM(lck); |
1870 | lck_rw_word_t word; | |
1871 | boolean_t gotlock = 0; | |
1872 | int slept = 0; | |
1873 | wait_result_t res = 0; | |
1874 | boolean_t istate; | |
5ba3f43e | 1875 | |
0a7de745 | 1876 | #if CONFIG_DTRACE |
5ba3f43e A |
1877 | uint64_t wait_interval = 0; |
1878 | int readers_at_sleep = 0; | |
1879 | boolean_t dtrace_ls_initialized = FALSE; | |
1880 | boolean_t dtrace_rwl_shared_spin, dtrace_rwl_shared_block, dtrace_ls_enabled = FALSE; | |
1881 | #endif /* CONFIG_DTRACE */ | |
1882 | ||
0a7de745 A |
1883 | while (!lck_rw_grab(lck, LCK_RW_GRAB_SHARED, FALSE)) { |
1884 | #if CONFIG_DTRACE | |
5ba3f43e A |
1885 | if (dtrace_ls_initialized == FALSE) { |
1886 | dtrace_ls_initialized = TRUE; | |
1887 | dtrace_rwl_shared_spin = (lockstat_probemap[LS_LCK_RW_LOCK_SHARED_SPIN] != 0); | |
1888 | dtrace_rwl_shared_block = (lockstat_probemap[LS_LCK_RW_LOCK_SHARED_BLOCK] != 0); | |
1889 | dtrace_ls_enabled = dtrace_rwl_shared_spin || dtrace_rwl_shared_block; | |
1890 | if (dtrace_ls_enabled) { | |
1891 | /* | |
1892 | * Either sleeping or spinning is happening, | |
1893 | * start a timing of our delay interval now. | |
1894 | */ | |
1895 | readers_at_sleep = lck->lck_rw_shared_count; | |
1896 | wait_interval = mach_absolute_time(); | |
1897 | } | |
1898 | } | |
1899 | #endif | |
1900 | ||
1901 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SHARED_SPIN_CODE) | DBG_FUNC_START, | |
0a7de745 | 1902 | trace_lck, lck->lck_rw_want_excl, lck->lck_rw_want_upgrade, 0, 0); |
5ba3f43e A |
1903 | |
1904 | gotlock = lck_rw_grab(lck, LCK_RW_GRAB_SHARED, TRUE); | |
1905 | ||
1906 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SHARED_SPIN_CODE) | DBG_FUNC_END, | |
0a7de745 | 1907 | trace_lck, lck->lck_rw_want_excl, lck->lck_rw_want_upgrade, gotlock, 0); |
5ba3f43e | 1908 | |
0a7de745 | 1909 | if (gotlock) { |
5ba3f43e | 1910 | break; |
0a7de745 | 1911 | } |
5ba3f43e A |
1912 | /* |
1913 | * if we get here, the deadline has expired w/o us | |
1914 | * being able to grab the lock for read | |
1915 | * check to see if we're allowed to do a thread_block | |
1916 | */ | |
1917 | if (lck->lck_rw_can_sleep) { | |
5ba3f43e A |
1918 | istate = lck_interlock_lock(lck); |
1919 | ||
1920 | word.data = ordered_load_rw(lck); | |
1921 | if ((word.want_excl || word.want_upgrade) && | |
1922 | ((word.shared_count == 0) || word.priv_excl)) { | |
5ba3f43e | 1923 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SHARED_WAIT_CODE) | DBG_FUNC_START, |
0a7de745 | 1924 | trace_lck, word.want_excl, word.want_upgrade, 0, 0); |
5ba3f43e A |
1925 | |
1926 | word.r_waiting = 1; | |
1927 | ordered_store_rw(lck, word.data); | |
1928 | ||
1929 | thread_set_pending_block_hint(current_thread(), kThreadWaitKernelRWLockRead); | |
d9a64523 | 1930 | res = assert_wait(LCK_RW_READER_EVENT(lck), |
0a7de745 | 1931 | THREAD_UNINT | THREAD_WAIT_NOREPORT_USER); |
5ba3f43e A |
1932 | lck_interlock_unlock(lck, istate); |
1933 | ||
1934 | if (res == THREAD_WAITING) { | |
1935 | res = thread_block(THREAD_CONTINUE_NULL); | |
1936 | slept++; | |
1937 | } | |
1938 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SHARED_WAIT_CODE) | DBG_FUNC_END, | |
0a7de745 | 1939 | trace_lck, res, slept, 0, 0); |
5ba3f43e A |
1940 | } else { |
1941 | word.shared_count++; | |
1942 | ordered_store_rw(lck, word.data); | |
1943 | lck_interlock_unlock(lck, istate); | |
1944 | break; | |
1945 | } | |
1946 | } | |
1947 | } | |
1948 | ||
0a7de745 | 1949 | #if CONFIG_DTRACE |
5ba3f43e A |
1950 | if (dtrace_ls_enabled == TRUE) { |
1951 | if (slept == 0) { | |
0a7de745 | 1952 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_SPIN, lck, mach_absolute_time() - wait_interval, 0); |
5ba3f43e | 1953 | } else { |
0a7de745 | 1954 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_BLOCK, lck, |
5ba3f43e A |
1955 | mach_absolute_time() - wait_interval, 0, |
1956 | (readers_at_sleep == 0 ? 1 : 0), readers_at_sleep); | |
1957 | } | |
1958 | } | |
1959 | LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_ACQUIRE, lck, 0); | |
0a7de745 | 1960 | #endif /* CONFIG_DTRACE */ |
5ba3f43e A |
1961 | } |
1962 | ||
f427ee49 A |
1963 | /* |
1964 | * Required to verify thread ownership for exclusive locks by virtue of PPL | |
1965 | * usage | |
1966 | */ | |
5ba3f43e A |
1967 | void |
1968 | lck_rw_assert( | |
0a7de745 A |
1969 | lck_rw_t *lck, |
1970 | unsigned int type) | |
5ba3f43e A |
1971 | { |
1972 | switch (type) { | |
1973 | case LCK_RW_ASSERT_SHARED: | |
1974 | if ((lck->lck_rw_shared_count != 0) && | |
1975 | (lck->lck_rw_owner == THREAD_NULL)) { | |
1976 | return; | |
1977 | } | |
1978 | break; | |
1979 | case LCK_RW_ASSERT_EXCLUSIVE: | |
1980 | if ((lck->lck_rw_want_excl || lck->lck_rw_want_upgrade) && | |
0a7de745 | 1981 | (lck->lck_rw_shared_count == 0) && |
5ba3f43e A |
1982 | (lck->lck_rw_owner == current_thread())) { |
1983 | return; | |
1984 | } | |
1985 | break; | |
1986 | case LCK_RW_ASSERT_HELD: | |
0a7de745 A |
1987 | if (lck->lck_rw_shared_count != 0) { |
1988 | return; // Held shared | |
1989 | } | |
5ba3f43e A |
1990 | if ((lck->lck_rw_want_excl || lck->lck_rw_want_upgrade) && |
1991 | (lck->lck_rw_owner == current_thread())) { | |
0a7de745 | 1992 | return; // Held exclusive |
5ba3f43e A |
1993 | } |
1994 | break; | |
1995 | case LCK_RW_ASSERT_NOTHELD: | |
1996 | if ((lck->lck_rw_shared_count == 0) && | |
0a7de745 | 1997 | !(lck->lck_rw_want_excl || lck->lck_rw_want_upgrade) && |
5ba3f43e A |
1998 | (lck->lck_rw_owner == THREAD_NULL)) { |
1999 | return; | |
2000 | } | |
2001 | break; | |
2002 | default: | |
2003 | break; | |
2004 | } | |
2005 | panic("rw lock (%p)%s held (mode=%u)", lck, (type == LCK_RW_ASSERT_NOTHELD ? "" : " not"), type); | |
2006 | } | |
2007 | ||
2008 | ||
2009 | /* | |
2010 | * Routine: kdp_lck_rw_lock_is_acquired_exclusive | |
2011 | * NOT SAFE: To be used only by kernel debugger to avoid deadlock. | |
2012 | */ | |
2013 | boolean_t | |
0a7de745 A |
2014 | kdp_lck_rw_lock_is_acquired_exclusive(lck_rw_t *lck) |
2015 | { | |
5ba3f43e A |
2016 | if (not_in_kdp) { |
2017 | panic("panic: rw lock exclusive check done outside of kernel debugger"); | |
2018 | } | |
2019 | return ((lck->lck_rw_want_upgrade || lck->lck_rw_want_excl) && (lck->lck_rw_shared_count == 0)) ? TRUE : FALSE; | |
2020 | } | |
2021 | ||
2022 | /* | |
2023 | * The C portion of the mutex package. These routines are only invoked | |
2024 | * if the optimized assembler routines can't do the work. | |
2025 | */ | |
2026 | ||
2027 | /* | |
2028 | * Forward declaration | |
2029 | */ | |
2030 | ||
0a7de745 | 2031 | void |
5ba3f43e | 2032 | lck_mtx_ext_init( |
0a7de745 A |
2033 | lck_mtx_ext_t * lck, |
2034 | lck_grp_t * grp, | |
2035 | lck_attr_t * attr); | |
5ba3f43e A |
2036 | |
2037 | /* | |
2038 | * Routine: lck_mtx_alloc_init | |
2039 | */ | |
2040 | lck_mtx_t * | |
2041 | lck_mtx_alloc_init( | |
0a7de745 A |
2042 | lck_grp_t * grp, |
2043 | lck_attr_t * attr) | |
5ba3f43e A |
2044 | { |
2045 | lck_mtx_t *lck; | |
2046 | ||
f427ee49 A |
2047 | lck = zalloc(ZV_LCK_MTX); |
2048 | lck_mtx_init(lck, grp, attr); | |
0a7de745 | 2049 | return lck; |
5ba3f43e A |
2050 | } |
2051 | ||
2052 | /* | |
2053 | * Routine: lck_mtx_free | |
2054 | */ | |
2055 | void | |
2056 | lck_mtx_free( | |
0a7de745 A |
2057 | lck_mtx_t * lck, |
2058 | lck_grp_t * grp) | |
5ba3f43e A |
2059 | { |
2060 | lck_mtx_destroy(lck, grp); | |
f427ee49 | 2061 | zfree(ZV_LCK_MTX, lck); |
5ba3f43e A |
2062 | } |
2063 | ||
2064 | /* | |
2065 | * Routine: lck_mtx_init | |
2066 | */ | |
2067 | void | |
2068 | lck_mtx_init( | |
0a7de745 A |
2069 | lck_mtx_t * lck, |
2070 | lck_grp_t * grp, | |
2071 | lck_attr_t * attr) | |
5ba3f43e | 2072 | { |
0a7de745 | 2073 | #ifdef BER_XXX |
5ba3f43e A |
2074 | lck_mtx_ext_t *lck_ext; |
2075 | #endif | |
2076 | lck_attr_t *lck_attr; | |
2077 | ||
0a7de745 | 2078 | if (attr != LCK_ATTR_NULL) { |
5ba3f43e | 2079 | lck_attr = attr; |
0a7de745 | 2080 | } else { |
5ba3f43e | 2081 | lck_attr = &LockDefaultLckAttr; |
0a7de745 | 2082 | } |
5ba3f43e | 2083 | |
0a7de745 | 2084 | #ifdef BER_XXX |
5ba3f43e | 2085 | if ((lck_attr->lck_attr_val) & LCK_ATTR_DEBUG) { |
f427ee49 A |
2086 | lck_ext = zalloc(ZV_LCK_MTX_EXT); |
2087 | lck_mtx_ext_init(lck_ext, grp, lck_attr); | |
2088 | lck->lck_mtx_tag = LCK_MTX_TAG_INDIRECT; | |
2089 | lck->lck_mtx_ptr = lck_ext; | |
2090 | lck->lck_mtx_type = LCK_MTX_TYPE; | |
5ba3f43e A |
2091 | } else |
2092 | #endif | |
2093 | { | |
0a7de745 | 2094 | lck->lck_mtx_ptr = NULL; // Clear any padding in the union fields below |
5ba3f43e | 2095 | lck->lck_mtx_waiters = 0; |
5ba3f43e A |
2096 | lck->lck_mtx_type = LCK_MTX_TYPE; |
2097 | ordered_store_mtx(lck, 0); | |
2098 | } | |
2099 | lck_grp_reference(grp); | |
2100 | lck_grp_lckcnt_incr(grp, LCK_TYPE_MTX); | |
2101 | } | |
2102 | ||
2103 | /* | |
2104 | * Routine: lck_mtx_init_ext | |
2105 | */ | |
2106 | void | |
2107 | lck_mtx_init_ext( | |
0a7de745 A |
2108 | lck_mtx_t * lck, |
2109 | lck_mtx_ext_t * lck_ext, | |
2110 | lck_grp_t * grp, | |
2111 | lck_attr_t * attr) | |
5ba3f43e A |
2112 | { |
2113 | lck_attr_t *lck_attr; | |
2114 | ||
0a7de745 | 2115 | if (attr != LCK_ATTR_NULL) { |
5ba3f43e | 2116 | lck_attr = attr; |
0a7de745 | 2117 | } else { |
5ba3f43e | 2118 | lck_attr = &LockDefaultLckAttr; |
0a7de745 | 2119 | } |
5ba3f43e A |
2120 | |
2121 | if ((lck_attr->lck_attr_val) & LCK_ATTR_DEBUG) { | |
2122 | lck_mtx_ext_init(lck_ext, grp, lck_attr); | |
2123 | lck->lck_mtx_tag = LCK_MTX_TAG_INDIRECT; | |
2124 | lck->lck_mtx_ptr = lck_ext; | |
2125 | lck->lck_mtx_type = LCK_MTX_TYPE; | |
2126 | } else { | |
2127 | lck->lck_mtx_waiters = 0; | |
5ba3f43e A |
2128 | lck->lck_mtx_type = LCK_MTX_TYPE; |
2129 | ordered_store_mtx(lck, 0); | |
2130 | } | |
2131 | lck_grp_reference(grp); | |
2132 | lck_grp_lckcnt_incr(grp, LCK_TYPE_MTX); | |
2133 | } | |
2134 | ||
2135 | /* | |
2136 | * Routine: lck_mtx_ext_init | |
2137 | */ | |
2138 | void | |
2139 | lck_mtx_ext_init( | |
0a7de745 A |
2140 | lck_mtx_ext_t * lck, |
2141 | lck_grp_t * grp, | |
2142 | lck_attr_t * attr) | |
5ba3f43e A |
2143 | { |
2144 | bzero((void *) lck, sizeof(lck_mtx_ext_t)); | |
2145 | ||
2146 | lck->lck_mtx.lck_mtx_type = LCK_MTX_TYPE; | |
2147 | ||
2148 | if ((attr->lck_attr_val) & LCK_ATTR_DEBUG) { | |
2149 | lck->lck_mtx_deb.type = MUTEX_TAG; | |
2150 | lck->lck_mtx_attr |= LCK_MTX_ATTR_DEBUG; | |
2151 | } | |
2152 | lck->lck_mtx_grp = grp; | |
2153 | ||
0a7de745 | 2154 | if (grp->lck_grp_attr & LCK_GRP_ATTR_STAT) { |
5ba3f43e | 2155 | lck->lck_mtx_attr |= LCK_MTX_ATTR_STAT; |
0a7de745 | 2156 | } |
5ba3f43e A |
2157 | } |
2158 | ||
2159 | /* The slow versions */ | |
2160 | static void lck_mtx_lock_contended(lck_mtx_t *lock, thread_t thread, boolean_t interlocked); | |
2161 | static boolean_t lck_mtx_try_lock_contended(lck_mtx_t *lock, thread_t thread); | |
2162 | static void lck_mtx_unlock_contended(lck_mtx_t *lock, thread_t thread, boolean_t interlocked); | |
2163 | ||
0a7de745 A |
2164 | /* The adaptive spin function */ |
2165 | static spinwait_result_t lck_mtx_lock_contended_spinwait_arm(lck_mtx_t *lock, thread_t thread, boolean_t interlocked); | |
2166 | ||
5ba3f43e A |
2167 | /* |
2168 | * Routine: lck_mtx_verify | |
2169 | * | |
2170 | * Verify if a mutex is valid | |
2171 | */ | |
2172 | static inline void | |
2173 | lck_mtx_verify(lck_mtx_t *lock) | |
2174 | { | |
0a7de745 | 2175 | if (lock->lck_mtx_type != LCK_MTX_TYPE) { |
5ba3f43e | 2176 | panic("Invalid mutex %p", lock); |
0a7de745 A |
2177 | } |
2178 | #if DEVELOPMENT || DEBUG | |
2179 | if (lock->lck_mtx_tag == LCK_MTX_TAG_DESTROYED) { | |
5ba3f43e | 2180 | panic("Mutex destroyed %p", lock); |
0a7de745 A |
2181 | } |
2182 | #endif /* DEVELOPMENT || DEBUG */ | |
5ba3f43e A |
2183 | } |
2184 | ||
2185 | /* | |
2186 | * Routine: lck_mtx_check_preemption | |
2187 | * | |
2188 | * Verify preemption is enabled when attempting to acquire a mutex. | |
2189 | */ | |
2190 | ||
2191 | static inline void | |
2192 | lck_mtx_check_preemption(lck_mtx_t *lock) | |
2193 | { | |
0a7de745 | 2194 | #if DEVELOPMENT || DEBUG |
f427ee49 A |
2195 | if (current_cpu_datap()->cpu_hibernate) { |
2196 | return; | |
2197 | } | |
2198 | ||
5ba3f43e A |
2199 | int pl = get_preemption_level(); |
2200 | ||
0a7de745 | 2201 | if (pl != 0) { |
5ba3f43e | 2202 | panic("Attempt to take mutex with preemption disabled. Lock=%p, level=%d", lock, pl); |
0a7de745 | 2203 | } |
5ba3f43e A |
2204 | #else |
2205 | (void)lock; | |
2206 | #endif | |
2207 | } | |
2208 | ||
2209 | /* | |
2210 | * Routine: lck_mtx_lock | |
2211 | */ | |
2212 | void | |
2213 | lck_mtx_lock(lck_mtx_t *lock) | |
2214 | { | |
0a7de745 | 2215 | thread_t thread; |
5ba3f43e A |
2216 | |
2217 | lck_mtx_verify(lock); | |
2218 | lck_mtx_check_preemption(lock); | |
2219 | thread = current_thread(); | |
cb323159 A |
2220 | if (os_atomic_cmpxchg(&lock->lck_mtx_data, |
2221 | 0, LCK_MTX_THREAD_TO_STATE(thread), acquire)) { | |
0a7de745 | 2222 | #if CONFIG_DTRACE |
5ba3f43e A |
2223 | LOCKSTAT_RECORD(LS_LCK_MTX_LOCK_ACQUIRE, lock, 0); |
2224 | #endif /* CONFIG_DTRACE */ | |
2225 | return; | |
2226 | } | |
2227 | lck_mtx_lock_contended(lock, thread, FALSE); | |
2228 | } | |
2229 | ||
2230 | /* | |
0a7de745 | 2231 | * This is the slow version of mutex locking. |
5ba3f43e A |
2232 | */ |
2233 | static void NOINLINE | |
2234 | lck_mtx_lock_contended(lck_mtx_t *lock, thread_t thread, boolean_t interlocked) | |
2235 | { | |
0a7de745 A |
2236 | thread_t holding_thread; |
2237 | uintptr_t state; | |
2238 | int waiters = 0; | |
2239 | spinwait_result_t sw_res; | |
cb323159 | 2240 | struct turnstile *ts = NULL; |
d9a64523 A |
2241 | |
2242 | /* Loop waiting until I see that the mutex is unowned */ | |
0a7de745 A |
2243 | for (;;) { |
2244 | sw_res = lck_mtx_lock_contended_spinwait_arm(lock, thread, interlocked); | |
2245 | interlocked = FALSE; | |
2246 | ||
2247 | switch (sw_res) { | |
2248 | case SPINWAIT_ACQUIRED: | |
cb323159 A |
2249 | if (ts != NULL) { |
2250 | interlock_lock(lock); | |
2251 | turnstile_complete((uintptr_t)lock, NULL, NULL, TURNSTILE_KERNEL_MUTEX); | |
2252 | interlock_unlock(lock); | |
2253 | } | |
0a7de745 A |
2254 | goto done; |
2255 | case SPINWAIT_INTERLOCK: | |
2256 | goto set_owner; | |
2257 | default: | |
2258 | break; | |
2259 | } | |
2260 | ||
5ba3f43e A |
2261 | state = ordered_load_mtx(lock); |
2262 | holding_thread = LCK_MTX_STATE_TO_THREAD(state); | |
0a7de745 | 2263 | if (holding_thread == NULL) { |
5ba3f43e | 2264 | break; |
0a7de745 | 2265 | } |
5ba3f43e | 2266 | ordered_store_mtx(lock, (state | LCK_ILOCK | ARM_LCK_WAITERS)); // Set waiters bit and wait |
cb323159 | 2267 | lck_mtx_lock_wait(lock, holding_thread, &ts); |
d9a64523 | 2268 | /* returns interlock unlocked */ |
5ba3f43e | 2269 | } |
d9a64523 | 2270 | |
0a7de745 | 2271 | set_owner: |
d9a64523 | 2272 | /* Hooray, I'm the new owner! */ |
0a7de745 A |
2273 | state = ordered_load_mtx(lock); |
2274 | ||
2275 | if (state & ARM_LCK_WAITERS) { | |
2276 | /* Skip lck_mtx_lock_acquire if there are no waiters. */ | |
cb323159 A |
2277 | waiters = lck_mtx_lock_acquire(lock, ts); |
2278 | /* | |
2279 | * lck_mtx_lock_acquire will call | |
2280 | * turnstile_complete | |
2281 | */ | |
2282 | } else { | |
2283 | if (ts != NULL) { | |
2284 | turnstile_complete((uintptr_t)lock, NULL, NULL, TURNSTILE_KERNEL_MUTEX); | |
2285 | } | |
0a7de745 A |
2286 | } |
2287 | ||
5ba3f43e | 2288 | state = LCK_MTX_THREAD_TO_STATE(thread); |
0a7de745 | 2289 | if (waiters != 0) { |
5ba3f43e | 2290 | state |= ARM_LCK_WAITERS; |
0a7de745 | 2291 | } |
0a7de745 A |
2292 | state |= LCK_ILOCK; // Preserve interlock |
2293 | ordered_store_mtx(lock, state); // Set ownership | |
2294 | interlock_unlock(lock); // Release interlock, enable preemption | |
0a7de745 A |
2295 | |
2296 | done: | |
5ba3f43e A |
2297 | load_memory_barrier(); |
2298 | ||
cb323159 A |
2299 | assert(thread->turnstile != NULL); |
2300 | ||
2301 | if (ts != NULL) { | |
2302 | turnstile_cleanup(); | |
2303 | } | |
2304 | ||
0a7de745 | 2305 | #if CONFIG_DTRACE |
5ba3f43e A |
2306 | LOCKSTAT_RECORD(LS_LCK_MTX_LOCK_ACQUIRE, lock, 0); |
2307 | #endif /* CONFIG_DTRACE */ | |
2308 | } | |
2309 | ||
0a7de745 A |
2310 | /* |
2311 | * Routine: lck_mtx_lock_spinwait_arm | |
2312 | * | |
2313 | * Invoked trying to acquire a mutex when there is contention but | |
2314 | * the holder is running on another processor. We spin for up to a maximum | |
2315 | * time waiting for the lock to be released. | |
2316 | */ | |
2317 | static spinwait_result_t | |
2318 | lck_mtx_lock_contended_spinwait_arm(lck_mtx_t *lock, thread_t thread, boolean_t interlocked) | |
2319 | { | |
2320 | int has_interlock = (int)interlocked; | |
0a7de745 | 2321 | __kdebug_only uintptr_t trace_lck = VM_KERNEL_UNSLIDE_OR_PERM(lock); |
ea3f0419 A |
2322 | thread_t owner, prev_owner; |
2323 | uint64_t window_deadline, sliding_deadline, high_deadline; | |
2324 | uint64_t start_time, cur_time, avg_hold_time, bias, delta; | |
2325 | int loopcount = 0; | |
2326 | uint i, prev_owner_cpu; | |
2327 | int total_hold_time_samples, window_hold_time_samples, unfairness; | |
2328 | bool owner_on_core, adjust; | |
2329 | uintptr_t state, new_state, waiters; | |
2330 | spinwait_result_t retval = SPINWAIT_DID_SPIN_HIGH_THR; | |
0a7de745 A |
2331 | |
2332 | if (__improbable(!(lck_mtx_adaptive_spin_mode & ADAPTIVE_SPIN_ENABLE))) { | |
2333 | if (!has_interlock) { | |
2334 | interlock_lock(lock); | |
2335 | } | |
2336 | ||
2337 | return SPINWAIT_DID_NOT_SPIN; | |
2338 | } | |
2339 | ||
0a7de745 A |
2340 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_MTX_LCK_SPIN_CODE) | DBG_FUNC_START, |
2341 | trace_lck, VM_KERNEL_UNSLIDE_OR_PERM(LCK_MTX_STATE_TO_THREAD(state)), lock->lck_mtx_waiters, 0, 0); | |
2342 | ||
ea3f0419 A |
2343 | start_time = mach_absolute_time(); |
2344 | /* | |
2345 | * window_deadline represents the "learning" phase. | |
2346 | * The thread collects statistics about the lock during | |
2347 | * window_deadline and then it makes a decision on whether to spin more | |
2348 | * or block according to the concurrency behavior | |
2349 | * observed. | |
2350 | * | |
2351 | * Every thread can spin at least low_MutexSpin. | |
2352 | */ | |
2353 | window_deadline = start_time + low_MutexSpin; | |
2354 | /* | |
2355 | * Sliding_deadline is the adjusted spin deadline | |
2356 | * computed after the "learning" phase. | |
2357 | */ | |
2358 | sliding_deadline = window_deadline; | |
2359 | /* | |
2360 | * High_deadline is a hard deadline. No thread | |
2361 | * can spin more than this deadline. | |
2362 | */ | |
2363 | if (high_MutexSpin >= 0) { | |
2364 | high_deadline = start_time + high_MutexSpin; | |
2365 | } else { | |
2366 | high_deadline = start_time + low_MutexSpin * real_ncpus; | |
0a7de745 A |
2367 | } |
2368 | ||
ea3f0419 A |
2369 | /* |
2370 | * Do not know yet which is the owner cpu. | |
2371 | * Initialize prev_owner_cpu with next cpu. | |
2372 | */ | |
2373 | prev_owner_cpu = (cpu_number() + 1) % real_ncpus; | |
2374 | total_hold_time_samples = 0; | |
2375 | window_hold_time_samples = 0; | |
2376 | avg_hold_time = 0; | |
2377 | adjust = TRUE; | |
2378 | bias = (os_hash_kernel_pointer(lock) + cpu_number()) % real_ncpus; | |
2379 | ||
0a7de745 A |
2380 | /* Snoop the lock state */ |
2381 | state = ordered_load_mtx(lock); | |
ea3f0419 A |
2382 | owner = LCK_MTX_STATE_TO_THREAD(state); |
2383 | prev_owner = owner; | |
2384 | ||
2385 | if (has_interlock) { | |
2386 | if (owner == NULL) { | |
2387 | retval = SPINWAIT_INTERLOCK; | |
2388 | goto done_spinning; | |
2389 | } else { | |
2390 | /* | |
2391 | * We are holding the interlock, so | |
2392 | * we can safely dereference owner. | |
2393 | */ | |
f427ee49 | 2394 | if (!machine_thread_on_core(owner) || (owner->state & TH_IDLE)) { |
ea3f0419 A |
2395 | retval = SPINWAIT_DID_NOT_SPIN; |
2396 | goto done_spinning; | |
2397 | } | |
2398 | } | |
2399 | interlock_unlock(lock); | |
2400 | has_interlock = 0; | |
2401 | } | |
0a7de745 A |
2402 | |
2403 | /* | |
2404 | * Spin while: | |
2405 | * - mutex is locked, and | |
2406 | * - it's locked as a spin lock, and | |
2407 | * - owner is running on another processor, and | |
0a7de745 A |
2408 | * - we haven't spun for long enough. |
2409 | */ | |
2410 | do { | |
ea3f0419 A |
2411 | /* |
2412 | * Try to acquire the lock. | |
2413 | */ | |
2414 | owner = LCK_MTX_STATE_TO_THREAD(state); | |
2415 | if (owner == NULL) { | |
2416 | waiters = state & ARM_LCK_WAITERS; | |
2417 | if (waiters) { | |
2418 | /* | |
2419 | * preserve the waiter bit | |
2420 | * and try acquire the interlock. | |
2421 | * Note: we will successfully acquire | |
2422 | * the interlock only if we can also | |
2423 | * acquire the lock. | |
2424 | */ | |
2425 | new_state = ARM_LCK_WAITERS | LCK_ILOCK; | |
2426 | has_interlock = 1; | |
2427 | retval = SPINWAIT_INTERLOCK; | |
2428 | disable_preemption(); | |
2429 | } else { | |
2430 | new_state = LCK_MTX_THREAD_TO_STATE(thread); | |
2431 | retval = SPINWAIT_ACQUIRED; | |
0a7de745 A |
2432 | } |
2433 | ||
ea3f0419 A |
2434 | /* |
2435 | * The cmpxchg will succed only if the lock | |
2436 | * is not owned (doesn't have an owner set) | |
2437 | * and it is not interlocked. | |
2438 | * It will not fail if there are waiters. | |
2439 | */ | |
2440 | if (os_atomic_cmpxchgv(&lock->lck_mtx_data, | |
2441 | waiters, new_state, &state, acquire)) { | |
2442 | goto done_spinning; | |
2443 | } else { | |
2444 | if (waiters) { | |
2445 | has_interlock = 0; | |
2446 | enable_preemption(); | |
2447 | } | |
2448 | } | |
2449 | } | |
0a7de745 | 2450 | |
ea3f0419 | 2451 | cur_time = mach_absolute_time(); |
0a7de745 | 2452 | |
ea3f0419 A |
2453 | /* |
2454 | * Never spin past high_deadline. | |
2455 | */ | |
2456 | if (cur_time >= high_deadline) { | |
2457 | retval = SPINWAIT_DID_SPIN_HIGH_THR; | |
2458 | break; | |
2459 | } | |
0a7de745 | 2460 | |
ea3f0419 A |
2461 | /* |
2462 | * Check if owner is on core. If not block. | |
2463 | */ | |
2464 | owner = LCK_MTX_STATE_TO_THREAD(state); | |
2465 | if (owner) { | |
2466 | i = prev_owner_cpu; | |
2467 | owner_on_core = FALSE; | |
0a7de745 | 2468 | |
ea3f0419 A |
2469 | disable_preemption(); |
2470 | state = ordered_load_mtx(lock); | |
2471 | owner = LCK_MTX_STATE_TO_THREAD(state); | |
0a7de745 | 2472 | |
ea3f0419 A |
2473 | /* |
2474 | * For scalability we want to check if the owner is on core | |
2475 | * without locking the mutex interlock. | |
2476 | * If we do not lock the mutex interlock, the owner that we see might be | |
2477 | * invalid, so we cannot dereference it. Therefore we cannot check | |
2478 | * any field of the thread to tell us if it is on core. | |
2479 | * Check if the thread that is running on the other cpus matches the owner. | |
2480 | */ | |
2481 | if (owner) { | |
2482 | do { | |
2483 | cpu_data_t *cpu_data_ptr = CpuDataEntries[i].cpu_data_vaddr; | |
2484 | if ((cpu_data_ptr != NULL) && (cpu_data_ptr->cpu_active_thread == owner)) { | |
2485 | owner_on_core = TRUE; | |
2486 | break; | |
0a7de745 | 2487 | } |
ea3f0419 A |
2488 | if (++i >= real_ncpus) { |
2489 | i = 0; | |
2490 | } | |
2491 | } while (i != prev_owner_cpu); | |
2492 | enable_preemption(); | |
2493 | ||
2494 | if (owner_on_core) { | |
2495 | prev_owner_cpu = i; | |
2496 | } else { | |
2497 | prev_owner = owner; | |
2498 | state = ordered_load_mtx(lock); | |
2499 | owner = LCK_MTX_STATE_TO_THREAD(state); | |
2500 | if (owner == prev_owner) { | |
2501 | /* | |
2502 | * Owner is not on core. | |
2503 | * Stop spinning. | |
2504 | */ | |
2505 | if (loopcount == 0) { | |
2506 | retval = SPINWAIT_DID_NOT_SPIN; | |
2507 | } else { | |
2508 | retval = SPINWAIT_DID_SPIN_OWNER_NOT_CORE; | |
2509 | } | |
2510 | break; | |
2511 | } | |
2512 | /* | |
2513 | * Fall through if the owner changed while we were scanning. | |
2514 | * The new owner could potentially be on core, so loop | |
2515 | * again. | |
2516 | */ | |
0a7de745 | 2517 | } |
ea3f0419 A |
2518 | } else { |
2519 | enable_preemption(); | |
0a7de745 A |
2520 | } |
2521 | } | |
2522 | ||
ea3f0419 A |
2523 | /* |
2524 | * Save how many times we see the owner changing. | |
2525 | * We can roughly estimate the the mutex hold | |
2526 | * time and the fairness with that. | |
2527 | */ | |
2528 | if (owner != prev_owner) { | |
2529 | prev_owner = owner; | |
2530 | total_hold_time_samples++; | |
2531 | window_hold_time_samples++; | |
0a7de745 A |
2532 | } |
2533 | ||
ea3f0419 A |
2534 | /* |
2535 | * Learning window expired. | |
2536 | * Try to adjust the sliding_deadline. | |
2537 | */ | |
2538 | if (cur_time >= window_deadline) { | |
2539 | /* | |
2540 | * If there was not contention during the window | |
2541 | * stop spinning. | |
2542 | */ | |
2543 | if (window_hold_time_samples < 1) { | |
2544 | retval = SPINWAIT_DID_SPIN_NO_WINDOW_CONTENTION; | |
2545 | break; | |
2546 | } | |
2547 | ||
2548 | if (adjust) { | |
2549 | /* | |
2550 | * For a fair lock, we'd wait for at most (NCPU-1) periods, | |
2551 | * but the lock is unfair, so let's try to estimate by how much. | |
2552 | */ | |
2553 | unfairness = total_hold_time_samples / real_ncpus; | |
2554 | ||
2555 | if (unfairness == 0) { | |
2556 | /* | |
2557 | * We observed the owner changing `total_hold_time_samples` times which | |
2558 | * let us estimate the average hold time of this mutex for the duration | |
2559 | * of the spin time. | |
2560 | * avg_hold_time = (cur_time - start_time) / total_hold_time_samples; | |
2561 | * | |
2562 | * In this case spin at max avg_hold_time * (real_ncpus - 1) | |
2563 | */ | |
2564 | delta = cur_time - start_time; | |
2565 | sliding_deadline = start_time + (delta * (real_ncpus - 1)) / total_hold_time_samples; | |
2566 | } else { | |
2567 | /* | |
2568 | * In this case at least one of the other cpus was able to get the lock twice | |
2569 | * while I was spinning. | |
2570 | * We could spin longer but it won't necessarily help if the system is unfair. | |
2571 | * Try to randomize the wait to reduce contention. | |
2572 | * | |
2573 | * We compute how much time we could potentially spin | |
2574 | * and distribute it over the cpus. | |
2575 | * | |
2576 | * bias is an integer between 0 and real_ncpus. | |
2577 | * distributed_increment = ((high_deadline - cur_time) / real_ncpus) * bias | |
2578 | */ | |
2579 | delta = high_deadline - cur_time; | |
2580 | sliding_deadline = cur_time + ((delta * bias) / real_ncpus); | |
2581 | adjust = FALSE; | |
2582 | } | |
2583 | } | |
0a7de745 | 2584 | |
ea3f0419 A |
2585 | window_deadline += low_MutexSpin; |
2586 | window_hold_time_samples = 0; | |
0a7de745 A |
2587 | } |
2588 | ||
ea3f0419 A |
2589 | /* |
2590 | * Stop spinning if we past | |
2591 | * the adjusted deadline. | |
2592 | */ | |
2593 | if (cur_time >= sliding_deadline) { | |
2594 | retval = SPINWAIT_DID_SPIN_SLIDING_THR; | |
2595 | break; | |
2596 | } | |
0a7de745 | 2597 | |
ea3f0419 A |
2598 | /* |
2599 | * We want to arm the monitor for wfe, | |
2600 | * so load exclusively the lock. | |
2601 | * | |
2602 | * NOTE: | |
2603 | * we rely on the fact that wfe will | |
2604 | * eventually return even if the cache line | |
2605 | * is not modified. This way we will keep | |
2606 | * looping and checking if the deadlines expired. | |
2607 | */ | |
2608 | state = os_atomic_load_exclusive(&lock->lck_mtx_data, relaxed); | |
2609 | owner = LCK_MTX_STATE_TO_THREAD(state); | |
2610 | if (owner != NULL) { | |
2611 | wait_for_event(); | |
2612 | state = ordered_load_mtx(lock); | |
2613 | } else { | |
2614 | atomic_exchange_abort(); | |
0a7de745 A |
2615 | } |
2616 | ||
2617 | loopcount++; | |
2618 | } while (TRUE); | |
2619 | ||
ea3f0419 | 2620 | done_spinning: |
0a7de745 A |
2621 | #if CONFIG_DTRACE |
2622 | /* | |
0a7de745 A |
2623 | * Note that we record a different probe id depending on whether |
2624 | * this is a direct or indirect mutex. This allows us to | |
2625 | * penalize only lock groups that have debug/stats enabled | |
2626 | * with dtrace processing if desired. | |
2627 | */ | |
2628 | if (__probable(lock->lck_mtx_tag != LCK_MTX_TAG_INDIRECT)) { | |
2629 | LOCKSTAT_RECORD(LS_LCK_MTX_LOCK_SPIN, lock, | |
ea3f0419 | 2630 | mach_absolute_time() - start_time); |
0a7de745 A |
2631 | } else { |
2632 | LOCKSTAT_RECORD(LS_LCK_MTX_EXT_LOCK_SPIN, lock, | |
ea3f0419 | 2633 | mach_absolute_time() - start_time); |
0a7de745 A |
2634 | } |
2635 | /* The lockstat acquire event is recorded by the caller. */ | |
2636 | #endif | |
2637 | ||
2638 | state = ordered_load_mtx(lock); | |
2639 | ||
2640 | KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_MTX_LCK_SPIN_CODE) | DBG_FUNC_END, | |
2641 | trace_lck, VM_KERNEL_UNSLIDE_OR_PERM(LCK_MTX_STATE_TO_THREAD(state)), lock->lck_mtx_waiters, retval, 0); | |
0a7de745 A |
2642 | if ((!has_interlock) && (retval != SPINWAIT_ACQUIRED)) { |
2643 | /* We must own either the lock or the interlock on return. */ | |
2644 | interlock_lock(lock); | |
2645 | } | |
2646 | ||
2647 | return retval; | |
2648 | } | |
2649 | ||
ea3f0419 | 2650 | |
5ba3f43e A |
2651 | /* |
2652 | * Common code for mutex locking as spinlock | |
2653 | */ | |
2654 | static inline void | |
2655 | lck_mtx_lock_spin_internal(lck_mtx_t *lock, boolean_t allow_held_as_mutex) | |
2656 | { | |
0a7de745 | 2657 | uintptr_t state; |
5ba3f43e A |
2658 | |
2659 | interlock_lock(lock); | |
2660 | state = ordered_load_mtx(lock); | |
2661 | if (LCK_MTX_STATE_TO_THREAD(state)) { | |
0a7de745 | 2662 | if (allow_held_as_mutex) { |
5ba3f43e | 2663 | lck_mtx_lock_contended(lock, current_thread(), TRUE); |
0a7de745 | 2664 | } else { |
5ba3f43e A |
2665 | // "Always" variants can never block. If the lock is held and blocking is not allowed |
2666 | // then someone is mixing always and non-always calls on the same lock, which is | |
2667 | // forbidden. | |
2668 | panic("Attempting to block on a lock taken as spin-always %p", lock); | |
0a7de745 | 2669 | } |
5ba3f43e A |
2670 | return; |
2671 | } | |
0a7de745 A |
2672 | state &= ARM_LCK_WAITERS; // Preserve waiters bit |
2673 | state |= (LCK_MTX_SPIN_TAG | LCK_ILOCK); // Add spin tag and maintain interlock | |
5ba3f43e A |
2674 | ordered_store_mtx(lock, state); |
2675 | load_memory_barrier(); | |
2676 | ||
0a7de745 | 2677 | #if CONFIG_DTRACE |
5ba3f43e A |
2678 | LOCKSTAT_RECORD(LS_LCK_MTX_LOCK_SPIN_ACQUIRE, lock, 0); |
2679 | #endif /* CONFIG_DTRACE */ | |
2680 | } | |
2681 | ||
2682 | /* | |
2683 | * Routine: lck_mtx_lock_spin | |
2684 | */ | |
2685 | void | |
2686 | lck_mtx_lock_spin(lck_mtx_t *lock) | |
2687 | { | |
2688 | lck_mtx_check_preemption(lock); | |
2689 | lck_mtx_lock_spin_internal(lock, TRUE); | |
2690 | } | |
2691 | ||
2692 | /* | |
2693 | * Routine: lck_mtx_lock_spin_always | |
2694 | */ | |
2695 | void | |
2696 | lck_mtx_lock_spin_always(lck_mtx_t *lock) | |
2697 | { | |
2698 | lck_mtx_lock_spin_internal(lock, FALSE); | |
2699 | } | |
2700 | ||
2701 | /* | |
2702 | * Routine: lck_mtx_try_lock | |
2703 | */ | |
2704 | boolean_t | |
2705 | lck_mtx_try_lock(lck_mtx_t *lock) | |
2706 | { | |
0a7de745 | 2707 | thread_t thread = current_thread(); |
5ba3f43e A |
2708 | |
2709 | lck_mtx_verify(lock); | |
cb323159 A |
2710 | if (os_atomic_cmpxchg(&lock->lck_mtx_data, |
2711 | 0, LCK_MTX_THREAD_TO_STATE(thread), acquire)) { | |
0a7de745 | 2712 | #if CONFIG_DTRACE |
5ba3f43e A |
2713 | LOCKSTAT_RECORD(LS_LCK_MTX_TRY_LOCK_ACQUIRE, lock, 0); |
2714 | #endif /* CONFIG_DTRACE */ | |
2715 | return TRUE; | |
2716 | } | |
2717 | return lck_mtx_try_lock_contended(lock, thread); | |
2718 | } | |
2719 | ||
2720 | static boolean_t NOINLINE | |
2721 | lck_mtx_try_lock_contended(lck_mtx_t *lock, thread_t thread) | |
2722 | { | |
0a7de745 A |
2723 | thread_t holding_thread; |
2724 | uintptr_t state; | |
2725 | int waiters; | |
5ba3f43e | 2726 | |
5ba3f43e A |
2727 | interlock_lock(lock); |
2728 | state = ordered_load_mtx(lock); | |
2729 | holding_thread = LCK_MTX_STATE_TO_THREAD(state); | |
2730 | if (holding_thread) { | |
2731 | interlock_unlock(lock); | |
2732 | return FALSE; | |
2733 | } | |
cb323159 | 2734 | waiters = lck_mtx_lock_acquire(lock, NULL); |
5ba3f43e | 2735 | state = LCK_MTX_THREAD_TO_STATE(thread); |
0a7de745 | 2736 | if (waiters != 0) { |
5ba3f43e | 2737 | state |= ARM_LCK_WAITERS; |
0a7de745 | 2738 | } |
0a7de745 A |
2739 | state |= LCK_ILOCK; // Preserve interlock |
2740 | ordered_store_mtx(lock, state); // Set ownership | |
2741 | interlock_unlock(lock); // Release interlock, enable preemption | |
5ba3f43e | 2742 | load_memory_barrier(); |
cb323159 A |
2743 | |
2744 | turnstile_cleanup(); | |
2745 | ||
5ba3f43e A |
2746 | return TRUE; |
2747 | } | |
2748 | ||
2749 | static inline boolean_t | |
2750 | lck_mtx_try_lock_spin_internal(lck_mtx_t *lock, boolean_t allow_held_as_mutex) | |
2751 | { | |
0a7de745 | 2752 | uintptr_t state; |
5ba3f43e | 2753 | |
0a7de745 | 2754 | if (!interlock_try(lock)) { |
5ba3f43e | 2755 | return FALSE; |
0a7de745 | 2756 | } |
5ba3f43e | 2757 | state = ordered_load_mtx(lock); |
0a7de745 | 2758 | if (LCK_MTX_STATE_TO_THREAD(state)) { |
5ba3f43e | 2759 | // Lock is held as mutex |
0a7de745 | 2760 | if (allow_held_as_mutex) { |
5ba3f43e | 2761 | interlock_unlock(lock); |
0a7de745 | 2762 | } else { |
5ba3f43e A |
2763 | // "Always" variants can never block. If the lock is held as a normal mutex |
2764 | // then someone is mixing always and non-always calls on the same lock, which is | |
2765 | // forbidden. | |
2766 | panic("Spin-mutex held as full mutex %p", lock); | |
0a7de745 | 2767 | } |
5ba3f43e A |
2768 | return FALSE; |
2769 | } | |
0a7de745 A |
2770 | state &= ARM_LCK_WAITERS; // Preserve waiters bit |
2771 | state |= (LCK_MTX_SPIN_TAG | LCK_ILOCK); // Add spin tag and maintain interlock | |
5ba3f43e A |
2772 | ordered_store_mtx(lock, state); |
2773 | load_memory_barrier(); | |
2774 | ||
0a7de745 | 2775 | #if CONFIG_DTRACE |
5ba3f43e A |
2776 | LOCKSTAT_RECORD(LS_LCK_MTX_TRY_SPIN_LOCK_ACQUIRE, lock, 0); |
2777 | #endif /* CONFIG_DTRACE */ | |
2778 | return TRUE; | |
2779 | } | |
2780 | ||
2781 | /* | |
2782 | * Routine: lck_mtx_try_lock_spin | |
2783 | */ | |
2784 | boolean_t | |
2785 | lck_mtx_try_lock_spin(lck_mtx_t *lock) | |
2786 | { | |
2787 | return lck_mtx_try_lock_spin_internal(lock, TRUE); | |
2788 | } | |
2789 | ||
2790 | /* | |
2791 | * Routine: lck_mtx_try_lock_spin_always | |
2792 | */ | |
2793 | boolean_t | |
2794 | lck_mtx_try_lock_spin_always(lck_mtx_t *lock) | |
2795 | { | |
2796 | return lck_mtx_try_lock_spin_internal(lock, FALSE); | |
2797 | } | |
2798 | ||
2799 | ||
2800 | ||
2801 | /* | |
2802 | * Routine: lck_mtx_unlock | |
2803 | */ | |
2804 | void | |
2805 | lck_mtx_unlock(lck_mtx_t *lock) | |
2806 | { | |
0a7de745 A |
2807 | thread_t thread = current_thread(); |
2808 | uintptr_t state; | |
2809 | boolean_t ilk_held = FALSE; | |
5ba3f43e A |
2810 | |
2811 | lck_mtx_verify(lock); | |
2812 | ||
2813 | state = ordered_load_mtx(lock); | |
2814 | if (state & LCK_ILOCK) { | |
0a7de745 A |
2815 | if (LCK_MTX_STATE_TO_THREAD(state) == (thread_t)LCK_MTX_SPIN_TAG) { |
2816 | ilk_held = TRUE; // Interlock is held by (presumably) this thread | |
2817 | } | |
5ba3f43e A |
2818 | goto slow_case; |
2819 | } | |
2820 | // Locked as a mutex | |
cb323159 A |
2821 | if (os_atomic_cmpxchg(&lock->lck_mtx_data, |
2822 | LCK_MTX_THREAD_TO_STATE(thread), 0, release)) { | |
0a7de745 | 2823 | #if CONFIG_DTRACE |
5ba3f43e A |
2824 | LOCKSTAT_RECORD(LS_LCK_MTX_UNLOCK_RELEASE, lock, 0); |
2825 | #endif /* CONFIG_DTRACE */ | |
2826 | return; | |
2827 | } | |
2828 | slow_case: | |
2829 | lck_mtx_unlock_contended(lock, thread, ilk_held); | |
2830 | } | |
2831 | ||
2832 | static void NOINLINE | |
2833 | lck_mtx_unlock_contended(lck_mtx_t *lock, thread_t thread, boolean_t ilk_held) | |
2834 | { | |
0a7de745 | 2835 | uintptr_t state; |
cb323159 | 2836 | boolean_t cleanup = FALSE; |
5ba3f43e A |
2837 | |
2838 | if (ilk_held) { | |
2839 | state = ordered_load_mtx(lock); | |
2840 | } else { | |
5ba3f43e A |
2841 | interlock_lock(lock); |
2842 | state = ordered_load_mtx(lock); | |
0a7de745 | 2843 | if (thread != LCK_MTX_STATE_TO_THREAD(state)) { |
5ba3f43e | 2844 | panic("lck_mtx_unlock(): Attempt to release lock not owned by thread (%p)", lock); |
0a7de745 | 2845 | } |
d9a64523 | 2846 | if (state & ARM_LCK_WAITERS) { |
cb323159 A |
2847 | if (lck_mtx_unlock_wakeup(lock, thread)) { |
2848 | state = ARM_LCK_WAITERS; | |
2849 | } else { | |
2850 | state = 0; | |
2851 | } | |
2852 | cleanup = TRUE; | |
2853 | goto unlock; | |
d9a64523 | 2854 | } |
5ba3f43e | 2855 | } |
d9a64523 | 2856 | state &= ARM_LCK_WAITERS; /* Clear state, retain waiters bit */ |
cb323159 | 2857 | unlock: |
5ba3f43e A |
2858 | state |= LCK_ILOCK; |
2859 | ordered_store_mtx(lock, state); | |
2860 | interlock_unlock(lock); | |
cb323159 A |
2861 | if (cleanup) { |
2862 | /* | |
2863 | * Do not do any turnstile operations outside of this block. | |
2864 | * lock/unlock is called at early stage of boot with single thread, | |
2865 | * when turnstile is not yet initialized. | |
2866 | * Even without contention we can come throught the slow path | |
2867 | * if the mutex is acquired as a spin lock. | |
2868 | */ | |
2869 | turnstile_cleanup(); | |
2870 | } | |
5ba3f43e | 2871 | |
0a7de745 | 2872 | #if CONFIG_DTRACE |
5ba3f43e A |
2873 | LOCKSTAT_RECORD(LS_LCK_MTX_UNLOCK_RELEASE, lock, 0); |
2874 | #endif /* CONFIG_DTRACE */ | |
2875 | } | |
2876 | ||
2877 | /* | |
2878 | * Routine: lck_mtx_assert | |
2879 | */ | |
2880 | void | |
2881 | lck_mtx_assert(lck_mtx_t *lock, unsigned int type) | |
2882 | { | |
0a7de745 A |
2883 | thread_t thread, holder; |
2884 | uintptr_t state; | |
5ba3f43e A |
2885 | |
2886 | state = ordered_load_mtx(lock); | |
2887 | holder = LCK_MTX_STATE_TO_THREAD(state); | |
2888 | if (holder == (thread_t)LCK_MTX_SPIN_TAG) { | |
0a7de745 A |
2889 | // Lock is held in spin mode, owner is unknown. |
2890 | return; // Punt | |
5ba3f43e A |
2891 | } |
2892 | thread = current_thread(); | |
2893 | if (type == LCK_MTX_ASSERT_OWNED) { | |
0a7de745 | 2894 | if (thread != holder) { |
5ba3f43e | 2895 | panic("lck_mtx_assert(): mutex (%p) owned", lock); |
0a7de745 | 2896 | } |
5ba3f43e | 2897 | } else if (type == LCK_MTX_ASSERT_NOTOWNED) { |
0a7de745 | 2898 | if (thread == holder) { |
5ba3f43e | 2899 | panic("lck_mtx_assert(): mutex (%p) not owned", lock); |
0a7de745 A |
2900 | } |
2901 | } else { | |
5ba3f43e | 2902 | panic("lck_mtx_assert(): invalid arg (%u)", type); |
0a7de745 | 2903 | } |
5ba3f43e A |
2904 | } |
2905 | ||
2906 | /* | |
2907 | * Routine: lck_mtx_ilk_unlock | |
2908 | */ | |
2909 | boolean_t | |
2910 | lck_mtx_ilk_unlock(lck_mtx_t *lock) | |
2911 | { | |
2912 | interlock_unlock(lock); | |
2913 | return TRUE; | |
2914 | } | |
2915 | ||
2916 | /* | |
2917 | * Routine: lck_mtx_convert_spin | |
2918 | * | |
2919 | * Convert a mutex held for spin into a held full mutex | |
2920 | */ | |
2921 | void | |
2922 | lck_mtx_convert_spin(lck_mtx_t *lock) | |
2923 | { | |
0a7de745 A |
2924 | thread_t thread = current_thread(); |
2925 | uintptr_t state; | |
2926 | int waiters; | |
5ba3f43e A |
2927 | |
2928 | state = ordered_load_mtx(lock); | |
0a7de745 A |
2929 | if (LCK_MTX_STATE_TO_THREAD(state) == thread) { |
2930 | return; // Already owned as mutex, return | |
2931 | } | |
2932 | if ((state & LCK_ILOCK) == 0 || (LCK_MTX_STATE_TO_THREAD(state) != (thread_t)LCK_MTX_SPIN_TAG)) { | |
5ba3f43e | 2933 | panic("lck_mtx_convert_spin: Not held as spinlock (%p)", lock); |
0a7de745 A |
2934 | } |
2935 | state &= ~(LCK_MTX_THREAD_MASK); // Clear the spin tag | |
5ba3f43e | 2936 | ordered_store_mtx(lock, state); |
cb323159 | 2937 | waiters = lck_mtx_lock_acquire(lock, NULL); // Acquire to manage priority boosts |
5ba3f43e | 2938 | state = LCK_MTX_THREAD_TO_STATE(thread); |
0a7de745 | 2939 | if (waiters != 0) { |
5ba3f43e | 2940 | state |= ARM_LCK_WAITERS; |
0a7de745 | 2941 | } |
5ba3f43e | 2942 | state |= LCK_ILOCK; |
0a7de745 A |
2943 | ordered_store_mtx(lock, state); // Set ownership |
2944 | interlock_unlock(lock); // Release interlock, enable preemption | |
cb323159 | 2945 | turnstile_cleanup(); |
5ba3f43e A |
2946 | } |
2947 | ||
2948 | ||
2949 | /* | |
2950 | * Routine: lck_mtx_destroy | |
2951 | */ | |
2952 | void | |
2953 | lck_mtx_destroy( | |
0a7de745 A |
2954 | lck_mtx_t * lck, |
2955 | lck_grp_t * grp) | |
5ba3f43e | 2956 | { |
0a7de745 | 2957 | if (lck->lck_mtx_type != LCK_MTX_TYPE) { |
5ba3f43e | 2958 | panic("Destroying invalid mutex %p", lck); |
0a7de745 A |
2959 | } |
2960 | if (lck->lck_mtx_tag == LCK_MTX_TAG_DESTROYED) { | |
5ba3f43e | 2961 | panic("Destroying previously destroyed lock %p", lck); |
0a7de745 | 2962 | } |
5ba3f43e A |
2963 | lck_mtx_assert(lck, LCK_MTX_ASSERT_NOTOWNED); |
2964 | lck->lck_mtx_tag = LCK_MTX_TAG_DESTROYED; | |
2965 | lck_grp_lckcnt_decr(grp, LCK_TYPE_MTX); | |
2966 | lck_grp_deallocate(grp); | |
2967 | return; | |
2968 | } | |
2969 | ||
2970 | /* | |
2971 | * Routine: lck_spin_assert | |
2972 | */ | |
2973 | void | |
2974 | lck_spin_assert(lck_spin_t *lock, unsigned int type) | |
2975 | { | |
0a7de745 A |
2976 | thread_t thread, holder; |
2977 | uintptr_t state; | |
5ba3f43e | 2978 | |
0a7de745 | 2979 | if (lock->type != LCK_SPIN_TYPE) { |
5ba3f43e | 2980 | panic("Invalid spinlock %p", lock); |
0a7de745 | 2981 | } |
5ba3f43e A |
2982 | |
2983 | state = lock->lck_spin_data; | |
2984 | holder = (thread_t)(state & ~LCK_ILOCK); | |
2985 | thread = current_thread(); | |
2986 | if (type == LCK_ASSERT_OWNED) { | |
0a7de745 | 2987 | if (holder == 0) { |
5ba3f43e | 2988 | panic("Lock not owned %p = %lx", lock, state); |
0a7de745 A |
2989 | } |
2990 | if (holder != thread) { | |
5ba3f43e | 2991 | panic("Lock not owned by current thread %p = %lx", lock, state); |
0a7de745 A |
2992 | } |
2993 | if ((state & LCK_ILOCK) == 0) { | |
5ba3f43e | 2994 | panic("Lock bit not set %p = %lx", lock, state); |
0a7de745 | 2995 | } |
5ba3f43e A |
2996 | } else if (type == LCK_ASSERT_NOTOWNED) { |
2997 | if (holder != 0) { | |
0a7de745 | 2998 | if (holder == thread) { |
5ba3f43e | 2999 | panic("Lock owned by current thread %p = %lx", lock, state); |
0a7de745 | 3000 | } |
5ba3f43e | 3001 | } |
0a7de745 | 3002 | } else { |
5ba3f43e | 3003 | panic("lck_spin_assert(): invalid arg (%u)", type); |
0a7de745 | 3004 | } |
5ba3f43e A |
3005 | } |
3006 | ||
3007 | boolean_t | |
3008 | lck_rw_lock_yield_shared(lck_rw_t *lck, boolean_t force_yield) | |
3009 | { | |
0a7de745 | 3010 | lck_rw_word_t word; |
5ba3f43e A |
3011 | |
3012 | lck_rw_assert(lck, LCK_RW_ASSERT_SHARED); | |
3013 | ||
3014 | word.data = ordered_load_rw(lck); | |
3015 | if (word.want_excl || word.want_upgrade || force_yield) { | |
3016 | lck_rw_unlock_shared(lck); | |
3017 | mutex_pause(2); | |
3018 | lck_rw_lock_shared(lck); | |
3019 | return TRUE; | |
3020 | } | |
3021 | ||
3022 | return FALSE; | |
3023 | } | |
3024 | ||
3025 | /* | |
3026 | * Routine: kdp_lck_mtx_lock_spin_is_acquired | |
3027 | * NOT SAFE: To be used only by kernel debugger to avoid deadlock. | |
3028 | */ | |
3029 | boolean_t | |
3030 | kdp_lck_mtx_lock_spin_is_acquired(lck_mtx_t *lck) | |
3031 | { | |
0a7de745 | 3032 | uintptr_t state; |
5ba3f43e A |
3033 | |
3034 | if (not_in_kdp) { | |
3035 | panic("panic: spinlock acquired check done outside of kernel debugger"); | |
3036 | } | |
3037 | state = ordered_load_mtx(lck); | |
0a7de745 | 3038 | if (state == LCK_MTX_TAG_DESTROYED) { |
5ba3f43e | 3039 | return FALSE; |
0a7de745 A |
3040 | } |
3041 | if (LCK_MTX_STATE_TO_THREAD(state) || (state & LCK_ILOCK)) { | |
5ba3f43e | 3042 | return TRUE; |
0a7de745 | 3043 | } |
5ba3f43e A |
3044 | return FALSE; |
3045 | } | |
3046 | ||
3047 | void | |
3048 | kdp_lck_mtx_find_owner(__unused struct waitq * waitq, event64_t event, thread_waitinfo_t * waitinfo) | |
3049 | { | |
3050 | lck_mtx_t * mutex = LCK_EVENT_TO_MUTEX(event); | |
3051 | waitinfo->context = VM_KERNEL_UNSLIDE_OR_PERM(mutex); | |
3052 | uintptr_t state = ordered_load_mtx(mutex); | |
3053 | thread_t holder = LCK_MTX_STATE_TO_THREAD(state); | |
3054 | if ((uintptr_t)holder == (uintptr_t)LCK_MTX_SPIN_TAG) { | |
3055 | waitinfo->owner = STACKSHOT_WAITOWNER_MTXSPIN; | |
3056 | } else { | |
3057 | assertf(state != (uintptr_t)LCK_MTX_TAG_DESTROYED, "state=0x%llx", (uint64_t)state); | |
3058 | assertf(state != (uintptr_t)LCK_MTX_TAG_INDIRECT, "state=0x%llx", (uint64_t)state); | |
3059 | waitinfo->owner = thread_tid(holder); | |
3060 | } | |
3061 | } | |
3062 | ||
3063 | void | |
3064 | kdp_rwlck_find_owner(__unused struct waitq * waitq, event64_t event, thread_waitinfo_t * waitinfo) | |
3065 | { | |
0a7de745 A |
3066 | lck_rw_t *rwlck = NULL; |
3067 | switch (waitinfo->wait_type) { | |
3068 | case kThreadWaitKernelRWLockRead: | |
3069 | rwlck = READ_EVENT_TO_RWLOCK(event); | |
3070 | break; | |
3071 | case kThreadWaitKernelRWLockWrite: | |
3072 | case kThreadWaitKernelRWLockUpgrade: | |
3073 | rwlck = WRITE_EVENT_TO_RWLOCK(event); | |
3074 | break; | |
3075 | default: | |
3076 | panic("%s was called with an invalid blocking type", __FUNCTION__); | |
3077 | break; | |
5ba3f43e A |
3078 | } |
3079 | waitinfo->context = VM_KERNEL_UNSLIDE_OR_PERM(rwlck); | |
3080 | waitinfo->owner = thread_tid(rwlck->lck_rw_owner); | |
3081 | } |