osfmk/kern/syscall_subr.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * @OSF_COPYRIGHT@
  24  */
  25 /*
  26  * Mach Operating System
  27  * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
  28  * All Rights Reserved.
  29  *
  30  * Permission to use, copy, modify and distribute this software and its
  31  * documentation is hereby granted, provided that both the copyright
  32  * notice and this permission notice appear in all copies of the
  33  * software, derivative works or modified versions, and any portions
  34  * thereof, and that both notices appear in supporting documentation.
  35  *
  36  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  37  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  38  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  39  *
  40  * Carnegie Mellon requests users of this software to return to
  41  *
  42  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  43  *  School of Computer Science
  44  *  Carnegie Mellon University
  45  *  Pittsburgh PA 15213-3890
  46  *
  47  * any improvements or extensions that they make and grant Carnegie Mellon
  48  * the rights to redistribute these changes.
  49  */
  50 /*
  51  */
  52
  53 #include <cpus.h>
  54
  55 #include <mach/boolean.h>
  56 #include <mach/thread_switch.h>
  57 #include <ipc/ipc_port.h>
  58 #include <ipc/ipc_space.h>
  59 #include <kern/counters.h>
  60 #include <kern/etap_macros.h>
  61 #include <kern/ipc_kobject.h>
  62 #include <kern/processor.h>
  63 #include <kern/sched.h>
  64 #include <kern/sched_prim.h>
  65 #include <kern/spl.h>
  66 #include <kern/task.h>
  67 #include <kern/thread.h>
  68 #include <kern/ast.h>
  69 #include <mach/policy.h>
  70
  71 #include <kern/syscall_subr.h>
  72 #include <mach/mach_host_server.h>
  73 #include <mach/mach_syscalls.h>
  74
  75 #include <kern/sf.h>
  76
  77 /*
  78  *      swtch and swtch_pri both attempt to context switch (logic in
  79  *      thread_block no-ops the context switch if nothing would happen).
  80  *      A boolean is returned that indicates whether there is anything
  81  *      else runnable.
  82  *
  83  *      This boolean can be used by a thread waiting on a
  84  *      lock or condition:  If FALSE is returned, the thread is justified
  85  *      in becoming a resource hog by continuing to spin because there's
  86  *      nothing else useful that the processor could do.  If TRUE is
  87  *      returned, the thread should make one more check on the
  88  *      lock and then be a good citizen and really suspend.
  89  */
  90
  91 #if             0
  92
  93 /* broken..do not enable */
  94
  95 swtch_continue()
  96 {
  97     boolean_t retval;
  98         register processor_t myprocessor;
  99
 100     mp_disable_preemption();
 101         myprocessor = current_processor();
 102         retval = (
 103 #if     NCPUS > 1
 104                myprocessor->runq.count > 0 ||
 105 #endif  /*NCPUS > 1*/
 106                myprocessor->processor_set->runq.count > 0);
 107         mp_enable_preemption();
 108         return retval;
 109 }
 110
 111 #endif
 112
 113 boolean_t
 114 swtch(void)
 115 {
 116         register processor_t    myprocessor;
 117         boolean_t                               result;
 118
 119         mp_disable_preemption();
 120         myprocessor = current_processor();
 121         if (
 122 #if     NCPUS > 1
 123                         myprocessor->runq.count == 0                                    &&
 124 #endif  /* NCPUS > 1 */
 125                         myprocessor->processor_set->runq.count == 0                     ) {
 126                 mp_enable_preemption();
 127
 128                 return (FALSE);
 129         }
 130         mp_enable_preemption();
 131
 132         counter(c_swtch_block++);
 133
 134         thread_block((void (*)(void)) 0);
 135
 136         mp_disable_preemption();
 137         myprocessor = current_processor();
 138         result =
 139 #if     NCPUS > 1
 140                 myprocessor->runq.count > 0                                                     ||
 141 #endif  /*NCPUS > 1*/
 142                 myprocessor->processor_set->runq.count > 0;
 143         mp_enable_preemption();
 144
 145         return (result);
 146 }
 147
 148 boolean_t
 149 swtch_pri(
 150         int                             pri)
 151 {
 152         thread_t                                self = current_thread();
 153         register processor_t    myprocessor;
 154         boolean_t                               result;
 155         sched_policy_t                  *policy;
 156         spl_t                                   s;
 157
 158         s = splsched();
 159         thread_lock(self);
 160         myprocessor = current_processor();
 161         if (
 162 #if     NCPUS > 1
 163                         myprocessor->runq.count == 0                                    &&
 164 #endif  /* NCPUS > 1 */
 165                         myprocessor->processor_set->runq.count == 0                     ) {
 166                 thread_unlock(self);
 167                 splx(s);
 168
 169                 return (FALSE);
 170         }
 171
 172         policy = &sched_policy[self->policy];
 173         thread_unlock(self);
 174         splx(s);
 175
 176         policy->sp_ops.sp_swtch_pri(policy, pri);
 177
 178         mp_disable_preemption();
 179         myprocessor = current_processor();
 180         result =
 181 #if     NCPUS > 1
 182                 myprocessor->runq.count > 0                                                     ||
 183 #endif  /*NCPUS > 1*/
 184                 myprocessor->processor_set->runq.count > 0;
 185         mp_enable_preemption();
 186
 187         return (result);
 188 }
 189
 190 /*
 191  *      thread_switch:
 192  *
 193  *      Context switch.  User may supply thread hint.
 194  */
 195 kern_return_t
 196 thread_switch(
 197         mach_port_name_t                thread_name,
 198         int                                             option,
 199         mach_msg_timeout_t              option_time)
 200 {
 201     register thread_t           self = current_thread();
 202     register thread_act_t       hint_act = THR_ACT_NULL;
 203         sched_policy_t                  *policy;
 204         spl_t                                   s;
 205
 206     /*
 207      *  Process option.
 208      */
 209     switch (option) {
 210
 211         case SWITCH_OPTION_NONE:
 212         case SWITCH_OPTION_DEPRESS:
 213         case SWITCH_OPTION_WAIT:
 214             break;
 215
 216         default:
 217             return (KERN_INVALID_ARGUMENT);
 218     }
 219
 220     if (thread_name != MACH_PORT_NULL) {
 221                 ipc_port_t                      port;
 222
 223                 if (ipc_port_translate_send(self->top_act->task->itk_space,
 224                                                                         thread_name, &port) == KERN_SUCCESS) {
 225                         ip_reference(port);
 226                         ip_unlock(port);
 227
 228                         hint_act = convert_port_to_act(port);
 229                         ipc_port_release(port);
 230                 }
 231         }
 232
 233         s = splsched();
 234         thread_lock(self);
 235         policy = &sched_policy[self->policy];
 236         thread_unlock(self);
 237         splx(s);
 238
 239     /*
 240      * This is a scheduling policy-dependent operation.
 241      * Call the routine associated with the thread's
 242      * scheduling policy.
 243      */
 244     return (policy->sp_ops.
 245                                 sp_thread_switch(policy, hint_act, option, option_time));
 246 }