osfmk/kern/syscall_subr.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 #include <mach/boolean.h>
  57 #include <mach/thread_switch.h>
  58 #include <ipc/ipc_port.h>
  59 #include <ipc/ipc_space.h>
  60 #include <kern/counters.h>
  61 #include <kern/etap_macros.h>
  62 #include <kern/ipc_kobject.h>
  63 #include <kern/processor.h>
  64 #include <kern/sched.h>
  65 #include <kern/sched_prim.h>
  66 #include <kern/spl.h>
  67 #include <kern/task.h>
  68 #include <kern/thread.h>
  69 #include <kern/ast.h>
  70 #include <mach/policy.h>
  71
  72 #include <kern/syscall_subr.h>
  73 #include <mach/mach_host_server.h>
  74 #include <mach/mach_syscalls.h>
  75
  76 #include <kern/mk_sp.h>
  77
  78 /*
  79  *      swtch and swtch_pri both attempt to context switch (logic in
  80  *      thread_block no-ops the context switch if nothing would happen).
  81  *      A boolean is returned that indicates whether there is anything
  82  *      else runnable.
  83  *
  84  *      This boolean can be used by a thread waiting on a
  85  *      lock or condition:  If FALSE is returned, the thread is justified
  86  *      in becoming a resource hog by continuing to spin because there's
  87  *      nothing else useful that the processor could do.  If TRUE is
  88  *      returned, the thread should make one more check on the
  89  *      lock and then be a good citizen and really suspend.
  90  */
  91
  92 void
  93 swtch_continue(void)
  94 {
  95         register processor_t    myprocessor;
  96     boolean_t                           result;
  97
  98     mp_disable_preemption();
  99         myprocessor = current_processor();
 100         result =                myprocessor->runq.count > 0                                     ||
 101                                 myprocessor->processor_set->runq.count > 0;
 102         mp_enable_preemption();
 103
 104         thread_syscall_return(result);
 105         /*NOTREACHED*/
 106 }
 107
 108 boolean_t
 109 swtch(void)
 110 {
 111         register processor_t    myprocessor;
 112         boolean_t                               result;
 113
 114         mp_disable_preemption();
 115         myprocessor = current_processor();
 116         if (            myprocessor->runq.count == 0                            &&
 117                         myprocessor->processor_set->runq.count == 0                     ) {
 118                 mp_enable_preemption();
 119
 120                 return (FALSE);
 121         }
 122         mp_enable_preemption();
 123
 124         counter(c_swtch_block++);
 125
 126         thread_block_reason(swtch_continue, AST_YIELD);
 127
 128         mp_disable_preemption();
 129         myprocessor = current_processor();
 130         result =                myprocessor->runq.count > 0                                     ||
 131                                 myprocessor->processor_set->runq.count > 0;
 132         mp_enable_preemption();
 133
 134         return (result);
 135 }
 136
 137 void
 138 swtch_pri_continue(void)
 139 {
 140         register processor_t    myprocessor;
 141     boolean_t                           result;
 142
 143         _mk_sp_thread_depress_abort(current_thread(), FALSE);
 144
 145     mp_disable_preemption();
 146         myprocessor = current_processor();
 147         result =                myprocessor->runq.count > 0                                     ||
 148                                 myprocessor->processor_set->runq.count > 0;
 149         mp_enable_preemption();
 150
 151         thread_syscall_return(result);
 152         /*NOTREACHED*/
 153 }
 154
 155 boolean_t
 156 swtch_pri(
 157         int                             pri)
 158 {
 159         register processor_t    myprocessor;
 160         boolean_t                               result;
 161
 162         mp_disable_preemption();
 163         myprocessor = current_processor();
 164         if (    myprocessor->runq.count == 0                                    &&
 165                         myprocessor->processor_set->runq.count == 0                     ) {
 166                 mp_enable_preemption();
 167
 168                 return (FALSE);
 169         }
 170         mp_enable_preemption();
 171
 172         counter(c_swtch_pri_block++);
 173
 174         _mk_sp_thread_depress_abstime(std_quantum);
 175
 176         thread_block_reason(swtch_pri_continue, AST_YIELD);
 177
 178         _mk_sp_thread_depress_abort(current_thread(), FALSE);
 179
 180         mp_disable_preemption();
 181         myprocessor = current_processor();
 182         result =        myprocessor->runq.count > 0                                             ||
 183                                 myprocessor->processor_set->runq.count > 0;
 184         mp_enable_preemption();
 185
 186         return (result);
 187 }
 188
 189 /*
 190  *      thread_switch:
 191  *
 192  *      Context switch.  User may supply thread hint.
 193  */
 194 kern_return_t
 195 thread_switch(
 196         mach_port_name_t                thread_name,
 197         int                                             option,
 198         mach_msg_timeout_t              option_time)
 199 {
 200     register thread_t           self = current_thread();
 201     register thread_act_t       hint_act = THR_ACT_NULL;
 202
 203     /*
 204      *  Process option.
 205      */
 206     switch (option) {
 207
 208         case SWITCH_OPTION_NONE:
 209         case SWITCH_OPTION_DEPRESS:
 210         case SWITCH_OPTION_WAIT:
 211             break;
 212
 213         default:
 214             return (KERN_INVALID_ARGUMENT);
 215     }
 216
 217     if (thread_name != MACH_PORT_NULL) {
 218                 ipc_port_t                      port;
 219
 220                 if (ipc_port_translate_send(self->top_act->task->itk_space,
 221                                                                         thread_name, &port) == KERN_SUCCESS) {
 222                         ip_reference(port);
 223                         ip_unlock(port);
 224
 225                         hint_act = convert_port_to_act(port);
 226                         ipc_port_release(port);
 227                 }
 228         }
 229
 230     return _mk_sp_thread_switch(hint_act, option, option_time);
 231 }