osfmk/kern/ast.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * @OSF_COPYRIGHT@
  27  */
  28 /*
  29  * Mach Operating System
  30  * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
  31  * All Rights Reserved.
  32  *
  33  * Permission to use, copy, modify and distribute this software and its
  34  * documentation is hereby granted, provided that both the copyright
  35  * notice and this permission notice appear in all copies of the
  36  * software, derivative works or modified versions, and any portions
  37  * thereof, and that both notices appear in supporting documentation.
  38  *
  39  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  40  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  41  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  42  *
  43  * Carnegie Mellon requests users of this software to return to
  44  *
  45  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  46  *  School of Computer Science
  47  *  Carnegie Mellon University
  48  *  Pittsburgh PA 15213-3890
  49  *
  50  * any improvements or extensions that they make and grant Carnegie Mellon
  51  * the rights to redistribute these changes.
  52  */
  53 /*
  54  */
  55
  56 /*
  57  *
  58  *      This file contains routines to check whether an ast is needed.
  59  *
  60  *      ast_check() - check whether ast is needed for interrupt or context
  61  *      switch.  Usually called by clock interrupt handler.
  62  *
  63  */
  64
  65 #include <cputypes.h>
  66 #include <cpus.h>
  67 #include <platforms.h>
  68
  69 #include <kern/ast.h>
  70 #include <kern/counters.h>
  71 #include <kern/cpu_number.h>
  72 #include <kern/misc_protos.h>
  73 #include <kern/queue.h>
  74 #include <kern/sched_prim.h>
  75 #include <kern/thread.h>
  76 #include <kern/thread_act.h>
  77 #include <kern/thread_swap.h>
  78 #include <kern/processor.h>
  79 #include <kern/spl.h>
  80 #include <mach/policy.h>
  81
  82 volatile ast_t need_ast[NCPUS];
  83
  84 void
  85 ast_init(void)
  86 {
  87 #ifndef MACHINE_AST
  88         register int i;
  89
  90         for (i=0; i<NCPUS; i++) {
  91                 need_ast[i] = AST_NONE;
  92         }
  93 #endif  /* MACHINE_AST */
  94 }
  95
  96 /*
  97  * Called at splsched.
  98  */
  99 void
 100 ast_taken(
 101         ast_t                   reasons,
 102         boolean_t               enable
 103 )
 104 {
 105         register thread_t               self = current_thread();
 106         register int                    mycpu = cpu_number();
 107         boolean_t                               preempt_trap = (reasons == AST_PREEMPTION);
 108
 109         reasons &= need_ast[mycpu];
 110         need_ast[mycpu] &= ~reasons;
 111
 112         /*
 113          * Handle ASTs for all threads
 114          * except idle processor threads.
 115          */
 116         if (!(self->state & TH_IDLE)) {
 117                 /*
 118                  * Check for urgent preemption.
 119                  */
 120                 if (    (reasons & AST_URGENT)                          &&
 121                                 wait_queue_assert_possible(self)                ) {
 122                         if (reasons & AST_PREEMPT) {
 123                                 counter(c_ast_taken_block++);
 124                                 thread_block_reason(THREAD_CONTINUE_NULL,
 125                                                                                 AST_PREEMPT | AST_URGENT);
 126                         }
 127
 128                         reasons &= ~AST_PREEMPTION;
 129                 }
 130
 131                 /*
 132                  * The kernel preempt traps
 133                  * skip all other ASTs.
 134                  */
 135                 if (!preempt_trap) {
 136                         ml_set_interrupts_enabled(enable);
 137
 138 #ifdef  MACH_BSD
 139                         /*
 140                          * Handle BSD hook.
 141                          */
 142                         if (reasons & AST_BSD) {
 143                                 extern void             bsd_ast(thread_act_t    act);
 144                                 thread_act_t    act = self->top_act;
 145
 146                                 thread_ast_clear(act, AST_BSD);
 147                                 bsd_ast(act);
 148                         }
 149 #endif
 150
 151                         /*
 152                          * Thread APC hook.
 153                          */
 154                         if (reasons & AST_APC)
 155                                 act_execute_returnhandlers();
 156
 157                         ml_set_interrupts_enabled(FALSE);
 158
 159                         /*
 160                          * Check for preemption.
 161                          */
 162                         if (reasons & AST_PREEMPT) {
 163                                 processor_t             myprocessor = current_processor();
 164
 165                                 if (csw_needed(self, myprocessor))
 166                                         reasons = AST_PREEMPT;
 167                                 else
 168                                         reasons = AST_NONE;
 169                         }
 170                         if (    (reasons & AST_PREEMPT)                         &&
 171                                         wait_queue_assert_possible(self)                ) {
 172                                 counter(c_ast_taken_block++);
 173                                 thread_block_reason(thread_exception_return, AST_PREEMPT);
 174                         }
 175                 }
 176         }
 177
 178         ml_set_interrupts_enabled(enable);
 179 }
 180
 181 /*
 182  * Called at splsched.
 183  */
 184 void
 185 ast_check(
 186         processor_t             processor)
 187 {
 188         register thread_t               self = processor->active_thread;
 189
 190         processor->current_pri = self->sched_pri;
 191         if (processor->state == PROCESSOR_RUNNING) {
 192                 register ast_t          preempt;
 193 processor_running:
 194
 195                 /*
 196                  *      Propagate thread ast to processor.
 197                  */
 198                 ast_propagate(self->top_act->ast);
 199
 200                 /*
 201                  *      Context switch check.
 202                  */
 203                 if ((preempt = csw_check(self, processor)) != AST_NONE)
 204                         ast_on(preempt);
 205         }
 206         else
 207         if (    processor->state == PROCESSOR_DISPATCHING       ||
 208                         processor->state == PROCESSOR_IDLE                      ) {
 209                 return;
 210         }
 211         else
 212         if (processor->state == PROCESSOR_SHUTDOWN)
 213                 goto processor_running;
 214 }