/*
- * Copyright (c) 2000-2012 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2017 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
-/*
- */
-
-/*
- *
- * This file contains routines to check whether an ast is needed.
- *
- * ast_check() - check whether ast is needed for interrupt or context
- * switch. Usually called by clock interrupt handler.
- *
- */
-
-#include <cputypes.h>
-#include <platforms.h>
#include <kern/ast.h>
#include <kern/counters.h>
-#include <kern/cpu_number.h>
#include <kern/misc_protos.h>
#include <kern/queue.h>
#include <kern/sched_prim.h>
#include <kern/thread.h>
#include <kern/processor.h>
#include <kern/spl.h>
+#include <kern/sfi.h>
#if CONFIG_TELEMETRY
#include <kern/telemetry.h>
#endif
-#include <kern/wait_queue.h>
+#include <kern/waitq.h>
#include <kern/ledger.h>
+#include <kern/machine.h>
+#include <kperf/kperf_kpc.h>
#include <mach/policy.h>
-#include <machine/trap.h> // for CHUD AST hook
-#include <machine/pal_routines.h>
#include <security/mac_mach_internal.h> // for MACF AST hook
+#include <stdatomic.h>
-volatile perfASTCallback perfASTHook;
-
+static void __attribute__((noinline, noreturn, disable_tail_calls))
+thread_preempted(__unused void* parameter, __unused wait_result_t result)
+{
+ /*
+ * We've been scheduled again after a userspace preemption,
+ * try again to return to userspace.
+ */
+ thread_exception_return();
+}
+/*
+ * AST_URGENT was detected while in kernel mode
+ * Called with interrupts disabled, returns the same way
+ * Must return to caller
+ */
void
-ast_init(void)
+ast_taken_kernel(void)
{
-}
+ assert(ml_get_interrupts_enabled() == FALSE);
-extern void chudxnu_thread_ast(thread_t); // XXX this should probably be in a header...
+ thread_t thread = current_thread();
+
+ /* Idle threads handle preemption themselves */
+ if ((thread->state & TH_IDLE)) {
+ ast_off(AST_PREEMPTION);
+ return;
+ }
+
+ /*
+ * It's possible for this to be called after AST_URGENT
+ * has already been handled, due to races in enable_preemption
+ */
+ if (ast_peek(AST_URGENT) != AST_URGENT)
+ return;
+
+ /*
+ * Don't preempt if the thread is already preparing to block.
+ * TODO: the thread can cheese this with clear_wait()
+ */
+ if (waitq_wait_possible(thread) == FALSE) {
+ /* Consume AST_URGENT or the interrupt will call us again */
+ ast_consume(AST_URGENT);
+ return;
+ }
+
+ /* TODO: Should we csw_check again to notice if conditions have changed? */
+
+ ast_t urgent_reason = ast_consume(AST_PREEMPTION);
+
+ assert(urgent_reason & AST_PREEMPT);
+
+ counter(c_ast_taken_block++);
+
+ thread_block_reason(THREAD_CONTINUE_NULL, NULL, urgent_reason);
+
+ assert(ml_get_interrupts_enabled() == FALSE);
+}
/*
- * Called at splsched.
+ * An AST flag was set while returning to user mode
+ * Called with interrupts disabled, returns with interrupts enabled
+ * May call continuation instead of returning
*/
void
-ast_taken(
- ast_t reasons,
- boolean_t enable
-)
+ast_taken_user(void)
{
- boolean_t preempt_trap = (reasons == AST_PREEMPTION);
- ast_t *myast = ast_pending();
- thread_t thread = current_thread();
- perfASTCallback perf_hook = perfASTHook;
+ assert(ml_get_interrupts_enabled() == FALSE);
+
+ thread_t thread = current_thread();
+
+ /* We are about to return to userspace, there must not be a pending wait */
+ assert(waitq_wait_possible(thread));
+ assert((thread->state & TH_IDLE) == 0);
+
+ /* TODO: Add more 'return to userspace' assertions here */
/*
- * CHUD hook - all threads including idle processor threads
+ * If this thread was urgently preempted in userspace,
+ * take the preemption before processing the ASTs.
+ * The trap handler will call us again if we have more ASTs, so it's
+ * safe to block in a continuation here.
*/
- if (perf_hook) {
- if (*myast & AST_CHUD_ALL) {
- (*perf_hook)(reasons, myast);
-
- if (*myast == AST_NONE)
- return;
- }
+ if (ast_peek(AST_URGENT) == AST_URGENT) {
+ ast_t urgent_reason = ast_consume(AST_PREEMPTION);
+
+ assert(urgent_reason & AST_PREEMPT);
+
+ /* TODO: Should we csw_check again to notice if conditions have changed? */
+
+ thread_block_reason(thread_preempted, NULL, urgent_reason);
+ /* NOTREACHED */
}
- else
- *myast &= ~AST_CHUD_ALL;
- reasons &= *myast;
- *myast &= ~reasons;
+ /*
+ * AST_KEVENT does not send an IPI when setting the ast for a thread running in parallel
+ * on a different processor. Only the ast bit on the thread will be set.
+ *
+ * Force a propagate for concurrent updates without an IPI.
+ */
+ ast_propagate(thread);
/*
- * Handle ASTs for all threads
- * except idle processor threads.
+ * Consume all non-preemption processor ASTs matching reasons
+ * because we're handling them here.
+ *
+ * If one of the AST handlers blocks in a continuation,
+ * we'll reinstate the unserviced thread-level AST flags
+ * from the thread to the processor on context switch.
+ * If one of the AST handlers sets another AST,
+ * the trap handler will call ast_taken_user again.
+ *
+ * We expect the AST handlers not to thread_exception_return
+ * without an ast_propagate or context switch to reinstate
+ * the per-processor ASTs.
+ *
+ * TODO: Why are AST_DTRACE and AST_KPERF not per-thread ASTs?
*/
- if (!(thread->state & TH_IDLE)) {
- /*
- * Check for urgent preemption.
- */
- if ( (reasons & AST_URGENT) &&
- wait_queue_assert_possible(thread) ) {
- if (reasons & AST_PREEMPT) {
- counter(c_ast_taken_block++);
- thread_block_reason(THREAD_CONTINUE_NULL, NULL,
- AST_PREEMPT | AST_URGENT);
- }
-
- reasons &= ~AST_PREEMPTION;
- }
+ ast_t reasons = ast_consume(AST_PER_THREAD | AST_KPERF | AST_DTRACE);
+
+ ml_set_interrupts_enabled(TRUE);
+
+#if CONFIG_DTRACE
+ if (reasons & AST_DTRACE) {
+ dtrace_ast();
+ }
+#endif
- /*
- * The kernel preempt traps
- * skip all other ASTs.
- */
- if (!preempt_trap) {
- ml_set_interrupts_enabled(enable);
-
-#ifdef MACH_BSD
- /*
- * Handle BSD hook.
- */
- if (reasons & AST_BSD) {
- thread_ast_clear(thread, AST_BSD);
- bsd_ast(thread);
- }
+#ifdef MACH_BSD
+ if (reasons & AST_BSD) {
+ thread_ast_clear(thread, AST_BSD);
+ bsd_ast(thread);
+ }
#endif
+
#if CONFIG_MACF
- /*
- * Handle MACF hook.
- */
- if (reasons & AST_MACF) {
- thread_ast_clear(thread, AST_MACF);
- mac_thread_userret(thread);
- }
+ if (reasons & AST_MACF) {
+ thread_ast_clear(thread, AST_MACF);
+ mac_thread_userret(thread);
+ }
#endif
- /*
- * Thread APC hook.
- */
- if (reasons & AST_APC)
- act_execute_returnhandlers();
-
- if (reasons & AST_GUARD) {
- thread_ast_clear(thread, AST_GUARD);
- guard_ast(thread);
- }
-
- if (reasons & AST_LEDGER) {
- thread_ast_clear(thread, AST_LEDGER);
- ledger_ast(thread);
- }
-
- /*
- * Kernel Profiling Hook
- */
- if (reasons & AST_KPERF) {
- thread_ast_clear(thread, AST_KPERF);
- chudxnu_thread_ast(thread);
- }
+
+ if (reasons & AST_APC) {
+ thread_ast_clear(thread, AST_APC);
+ thread_apc_ast(thread);
+ }
+
+ if (reasons & AST_GUARD) {
+ thread_ast_clear(thread, AST_GUARD);
+ guard_ast(thread);
+ }
+
+ if (reasons & AST_LEDGER) {
+ thread_ast_clear(thread, AST_LEDGER);
+ ledger_ast(thread);
+ }
+
+ if (reasons & AST_KPERF) {
+ thread_ast_clear(thread, AST_KPERF);
+ kperf_kpc_thread_ast(thread);
+ }
+
+ if (reasons & AST_KEVENT) {
+ thread_ast_clear(thread, AST_KEVENT);
+ uint16_t bits = atomic_exchange(&thread->kevent_ast_bits, 0);
+ if (bits) kevent_ast(thread, bits);
+ }
#if CONFIG_TELEMETRY
- if (reasons & AST_TELEMETRY_ALL) {
- boolean_t interrupted_userspace;
-
- assert((reasons & AST_TELEMETRY_ALL) != AST_TELEMETRY_ALL); /* only one is valid at a time */
- interrupted_userspace = (reasons & AST_TELEMETRY_USER) ? TRUE : FALSE;
- thread_ast_clear(thread, AST_TELEMETRY_ALL);
- telemetry_ast(thread, interrupted_userspace);
- }
+ if (reasons & AST_TELEMETRY_ALL) {
+ ast_t telemetry_reasons = reasons & AST_TELEMETRY_ALL;
+ thread_ast_clear(thread, AST_TELEMETRY_ALL);
+ telemetry_ast(thread, telemetry_reasons);
+ }
+#endif
+
+ spl_t s = splsched();
+
+#if CONFIG_SCHED_SFI
+ /*
+ * SFI is currently a per-processor AST, not a per-thread AST
+ * TODO: SFI should be a per-thread AST
+ */
+ if (ast_consume(AST_SFI) == AST_SFI) {
+ sfi_ast(thread);
+ }
#endif
- ml_set_interrupts_enabled(FALSE);
+ /* We are about to return to userspace, there must not be a pending wait */
+ assert(waitq_wait_possible(thread));
+
+ /*
+ * We've handled all per-thread ASTs, time to handle non-urgent preemption.
+ *
+ * We delay reading the preemption bits until now in case the thread
+ * blocks while handling per-thread ASTs.
+ *
+ * If one of the AST handlers had managed to set a new AST bit,
+ * thread_exception_return will call ast_taken again.
+ */
+ ast_t preemption_reasons = ast_consume(AST_PREEMPTION);
+
+ if (preemption_reasons & AST_PREEMPT) {
+ /* Conditions may have changed from when the AST_PREEMPT was originally set, so re-check. */
- /*
- * Check for preemption.
- */
- if (reasons & AST_PREEMPT)
- reasons = csw_check(current_processor());
+ thread_lock(thread);
+ preemption_reasons = csw_check(current_processor(), (preemption_reasons & AST_QUANTUM));
+ thread_unlock(thread);
- if ( (reasons & AST_PREEMPT) &&
- wait_queue_assert_possible(thread) ) {
- counter(c_ast_taken_block++);
- thread_block_reason((thread_continue_t)thread_exception_return, NULL, AST_PREEMPT);
- }
+#if CONFIG_SCHED_SFI
+ /* csw_check might tell us that SFI is needed */
+ if (preemption_reasons & AST_SFI) {
+ sfi_ast(thread);
+ }
+#endif
+
+ if (preemption_reasons & AST_PREEMPT) {
+ counter(c_ast_taken_block++);
+ /* switching to a continuation implicitly re-enables interrupts */
+ thread_block_reason(thread_preempted, NULL, preemption_reasons);
+ /* NOTREACHED */
}
}
- ml_set_interrupts_enabled(enable);
+ splx(s);
}
/*
- * Called at splsched.
+ * Handle preemption IPI or IPI in response to setting an AST flag
+ * Triggered by cause_ast_check
+ * Called at splsched
*/
void
-ast_check(
- processor_t processor)
+ast_check(processor_t processor)
{
- thread_t thread = processor->active_thread;
+ if (processor->state != PROCESSOR_RUNNING &&
+ processor->state != PROCESSOR_SHUTDOWN)
+ return;
+
+ thread_t thread = processor->active_thread;
+ assert(thread == current_thread());
+
+ thread_lock(thread);
+
+ /*
+ * Propagate thread ast to processor.
+ * (handles IPI in response to setting AST flag)
+ */
+ ast_propagate(thread);
+
+ boolean_t needs_callout = false;
processor->current_pri = thread->sched_pri;
- processor->current_thmode = thread->sched_mode;
- if ( processor->state == PROCESSOR_RUNNING ||
- processor->state == PROCESSOR_SHUTDOWN ) {
- ast_t preempt;
-
- /*
- * Propagate thread ast to processor.
- */
- pal_ast_check(thread);
-
- ast_propagate(thread->ast);
-
- /*
- * Context switch check.
- */
- if ((preempt = csw_check(processor)) != AST_NONE)
- ast_on(preempt);
+ processor->current_sfi_class = thread->sfi_class = sfi_thread_classify(thread);
+ processor->current_recommended_pset_type = recommended_pset_type(thread);
+ perfcontrol_class_t thread_class = thread_get_perfcontrol_class(thread);
+ if (thread_class != processor->current_perfctl_class) {
+ /* We updated the perfctl class of this thread from another core.
+ * Since we dont do CLPC callouts from another core, do a callout
+ * here to let CLPC know that the currently running thread has a new
+ * class.
+ */
+ needs_callout = true;
}
+ processor->current_perfctl_class = thread_class;
+
+ ast_t preempt;
+
+ if ((preempt = csw_check(processor, AST_NONE)) != AST_NONE)
+ ast_on(preempt);
+
+ thread_unlock(thread);
+
+ if (needs_callout) {
+ machine_switch_perfcontrol_state_update(PERFCONTROL_ATTR_UPDATE,
+ mach_approximate_time(), 0, thread);
+ }
+}
+
+/*
+ * Set AST flags on current processor
+ * Called at splsched
+ */
+void
+ast_on(ast_t reasons)
+{
+ ast_t *pending_ast = ast_pending();
+
+ *pending_ast |= reasons;
+}
+
+/*
+ * Clear AST flags on current processor
+ * Called at splsched
+ */
+void
+ast_off(ast_t reasons)
+{
+ ast_t *pending_ast = ast_pending();
+
+ *pending_ast &= ~reasons;
}
+
+/*
+ * Consume the requested subset of the AST flags set on the processor
+ * Return the bits that were set
+ * Called at splsched
+ */
+ast_t
+ast_consume(ast_t reasons)
+{
+ ast_t *pending_ast = ast_pending();
+
+ reasons &= *pending_ast;
+ *pending_ast &= ~reasons;
+
+ return reasons;
+}
+
+/*
+ * Read the requested subset of the AST flags set on the processor
+ * Return the bits that were set, don't modify the processor
+ * Called at splsched
+ */
+ast_t
+ast_peek(ast_t reasons)
+{
+ ast_t *pending_ast = ast_pending();
+
+ reasons &= *pending_ast;
+
+ return reasons;
+}
+
+/*
+ * Re-set current processor's per-thread AST flags to those set on thread
+ * Called at splsched
+ */
+void
+ast_context(thread_t thread)
+{
+ ast_t *pending_ast = ast_pending();
+
+ *pending_ast = ((*pending_ast & ~AST_PER_THREAD) | thread->ast);
+}
+
+/*
+ * Propagate ASTs set on a thread to the current processor
+ * Called at splsched
+ */
+void
+ast_propagate(thread_t thread)
+{
+ ast_on(thread->ast);
+}
+
+void
+ast_dtrace_on(void)
+{
+ ast_on(AST_DTRACE);
+}
+
+
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