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Annotation of OSKit-Mach/kern/ipc_sched.c, revision 1.1

1.1     ! root        1: /* 
        !             2:  * Mach Operating System
        !             3:  * Copyright (c) 1993, 1992,1991,1990 Carnegie Mellon University
        !             4:  * All Rights Reserved.
        !             5:  * 
        !             6:  * Permission to use, copy, modify and distribute this software and its
        !             7:  * documentation is hereby granted, provided that both the copyright
        !             8:  * notice and this permission notice appear in all copies of the
        !             9:  * software, derivative works or modified versions, and any portions
        !            10:  * thereof, and that both notices appear in supporting documentation.
        !            11:  * 
        !            12:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
        !            13:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
        !            14:  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            15:  * 
        !            16:  * Carnegie Mellon requests users of this software to return to
        !            17:  * 
        !            18:  *  Software Distribution Coordinator  or  [email protected]
        !            19:  *  School of Computer Science
        !            20:  *  Carnegie Mellon University
        !            21:  *  Pittsburgh PA 15213-3890
        !            22:  * 
        !            23:  * any improvements or extensions that they make and grant Carnegie Mellon
        !            24:  * the rights to redistribute these changes.
        !            25:  */
        !            26: 
        !            27: #include <cpus.h>
        !            28: #include <mach_host.h>
        !            29: 
        !            30: #include <mach/message.h>
        !            31: #include <kern/counters.h>
        !            32: #include "cpu_number.h"
        !            33: #include <kern/lock.h>
        !            34: #include <kern/thread.h>
        !            35: #include <kern/sched_prim.h>
        !            36: #include <kern/processor.h>
        !            37: #include <kern/time_out.h>
        !            38: #include <kern/thread_swap.h>
        !            39: #include <kern/ipc_sched.h>
        !            40: #include <machine/machspl.h>   /* for splsched/splx */
        !            41: #include <machine/pmap.h>
        !            42: 
        !            43: 
        !            44: 
        !            45: /*
        !            46:  *     These functions really belong in kern/sched_prim.c.
        !            47:  */
        !            48: 
        !            49: /*
        !            50:  *     Routine:        thread_go
        !            51:  *     Purpose:
        !            52:  *             Start a thread running.
        !            53:  *     Conditions:
        !            54:  *             IPC locks may be held.
        !            55:  */
        !            56: 
        !            57: void
        !            58: thread_go(
        !            59:        thread_t thread)
        !            60: {
        !            61:        int     state;
        !            62:        spl_t   s;
        !            63: 
        !            64:        s = splsched();
        !            65:        thread_lock(thread);
        !            66: 
        !            67:        reset_timeout_check(&thread->timer);
        !            68: 
        !            69:        state = thread->state;
        !            70:        switch (state & TH_SCHED_STATE) {
        !            71: 
        !            72:            case TH_WAIT | TH_SUSP | TH_UNINT:
        !            73:            case TH_WAIT           | TH_UNINT:
        !            74:            case TH_WAIT:
        !            75:                /*
        !            76:                 *      Sleeping and not suspendable - put
        !            77:                 *      on run queue.
        !            78:                 */
        !            79:                thread->state = (state &~ TH_WAIT) | TH_RUN;
        !            80:                thread->wait_result = THREAD_AWAKENED;
        !            81:                thread_setrun(thread, TRUE);
        !            82:                break;
        !            83: 
        !            84:            case          TH_WAIT | TH_SUSP:
        !            85:            case TH_RUN | TH_WAIT:
        !            86:            case TH_RUN | TH_WAIT | TH_SUSP:
        !            87:            case TH_RUN | TH_WAIT           | TH_UNINT:
        !            88:            case TH_RUN | TH_WAIT | TH_SUSP | TH_UNINT:
        !            89:                /*
        !            90:                 *      Either already running, or suspended.
        !            91:                 */
        !            92:                thread->state = state & ~TH_WAIT;
        !            93:                thread->wait_result = THREAD_AWAKENED;
        !            94:                break;
        !            95: 
        !            96:            default:
        !            97:                /*
        !            98:                 *      Not waiting.
        !            99:                 */
        !           100:                break;
        !           101:        }
        !           102: 
        !           103:        thread_unlock(thread);
        !           104:        splx(s);
        !           105: }
        !           106: 
        !           107: /*
        !           108:  *     Routine:        thread_will_wait
        !           109:  *     Purpose:
        !           110:  *             Assert that the thread intends to block.
        !           111:  */
        !           112: 
        !           113: void
        !           114: thread_will_wait(
        !           115:        thread_t thread)
        !           116: {
        !           117:        spl_t   s;
        !           118: 
        !           119:        s = splsched();
        !           120:        thread_lock(thread);
        !           121: 
        !           122:        assert(thread->wait_result = -1);       /* for later assertions */
        !           123:        thread->state |= TH_WAIT;
        !           124: 
        !           125:        thread_unlock(thread);
        !           126:        splx(s);
        !           127: }
        !           128: 
        !           129: /*
        !           130:  *     Routine:        thread_will_wait_with_timeout
        !           131:  *     Purpose:
        !           132:  *             Assert that the thread intends to block,
        !           133:  *             with a timeout.
        !           134:  */
        !           135: 
        !           136: void
        !           137: thread_will_wait_with_timeout(
        !           138:        thread_t thread,
        !           139:        mach_msg_timeout_t msecs)
        !           140: {
        !           141:        natural_t ticks = convert_ipc_timeout_to_ticks(msecs);
        !           142:        spl_t   s;
        !           143: 
        !           144:        s = splsched();
        !           145:        thread_lock(thread);
        !           146: 
        !           147:        assert(thread->wait_result = -1);       /* for later assertions */
        !           148:        thread->state |= TH_WAIT;
        !           149: 
        !           150:        set_timeout(&thread->timer, ticks);
        !           151: 
        !           152:        thread_unlock(thread);
        !           153:        splx(s);
        !           154: }
        !           155: 
        !           156: #if    MACH_HOST
        !           157: #define check_processor_set(thread)    \
        !           158:            (current_processor()->processor_set == (thread)->processor_set)
        !           159: #else  /* MACH_HOST */
        !           160: #define        check_processor_set(thread)     TRUE
        !           161: #endif /* MACH_HOST */
        !           162: 
        !           163: #if    NCPUS > 1
        !           164: #define        check_bound_processor(thread) \
        !           165:            ((thread)->bound_processor == PROCESSOR_NULL || \
        !           166:             (thread)->bound_processor == current_processor())
        !           167: #else  /* NCPUS > 1 */
        !           168: #define        check_bound_processor(thread)   TRUE
        !           169: #endif /* NCPUS > 1 */
        !           170: 
        !           171: #ifdef CONTINUATIONS
        !           172: /*
        !           173:  *     Routine:        thread_handoff
        !           174:  *     Purpose:
        !           175:  *             Switch to a new thread (new), leaving the current
        !           176:  *             thread (old) blocked.  If successful, moves the
        !           177:  *             kernel stack from old to new and returns as the
        !           178:  *             new thread.  An explicit continuation for the old thread
        !           179:  *             must be supplied.
        !           180:  *
        !           181:  *             NOTE:  Although we wakeup new, we don't set new->wait_result.
        !           182:  *     Returns:
        !           183:  *             TRUE if the handoff happened.
        !           184:  */
        !           185: 
        !           186: boolean_t
        !           187: thread_handoff(
        !           188:        register thread_t old,
        !           189:        register continuation_t continuation,
        !           190:        register thread_t new)
        !           191: {
        !           192:        spl_t   s;
        !           193: 
        !           194:        assert(current_thread() == old);
        !           195: 
        !           196:        /*
        !           197:         *      XXX Dubious things here:
        !           198:         *      I don't check the idle_count on the processor set.
        !           199:         *      No scheduling priority or policy checks.
        !           200:         *      I assume the new thread is interruptible.
        !           201:         */
        !           202: 
        !           203:        s = splsched();
        !           204:        thread_lock(new);
        !           205: 
        !           206:        /*
        !           207:         *      The first thing we must do is check the state
        !           208:         *      of the threads, to ensure we can handoff.
        !           209:         *      This check uses current_processor()->processor_set,
        !           210:         *      which we can read without locking.
        !           211:         */
        !           212: 
        !           213:        if ((old->stack_privilege == current_stack()) ||
        !           214:            (new->state != (TH_WAIT|TH_SWAPPED)) ||
        !           215:             !check_processor_set(new) ||
        !           216:             !check_bound_processor(new)) {
        !           217:                thread_unlock(new);
        !           218:                (void) splx(s);
        !           219: 
        !           220:                counter_always(c_thread_handoff_misses++);
        !           221:                return FALSE;
        !           222:        }
        !           223: 
        !           224:        reset_timeout_check(&new->timer);
        !           225: 
        !           226:        new->state = TH_RUN;
        !           227:        thread_unlock(new);
        !           228: 
        !           229: #if    NCPUS > 1
        !           230:        new->last_processor = current_processor();
        !           231: #endif /* NCPUS > 1 */
        !           232: 
        !           233:        ast_context(new, cpu_number());
        !           234:        timer_switch(&new->system_timer);
        !           235: 
        !           236:        /*
        !           237:         *      stack_handoff is machine-dependent.  It does the
        !           238:         *      machine-dependent components of a context-switch, like
        !           239:         *      changing address spaces.  It updates active_threads.
        !           240:         */
        !           241: 
        !           242:        stack_handoff(old, new);
        !           243: 
        !           244:        /*
        !           245:         *      Now we must dispose of the old thread.
        !           246:         *      This is like thread_continue, except
        !           247:         *      that the old thread isn't waiting yet.
        !           248:         */
        !           249: 
        !           250:        thread_lock(old);
        !           251:        old->swap_func = continuation;
        !           252:        assert(old->wait_result = -1);          /* for later assertions */
        !           253: 
        !           254:        if (old->state == TH_RUN) {
        !           255:                /*
        !           256:                 *      This is our fast path.
        !           257:                 */
        !           258: 
        !           259:                old->state = TH_WAIT|TH_SWAPPED;
        !           260:        }
        !           261:        else if (old->state == (TH_RUN|TH_SUSP)) {
        !           262:                /*
        !           263:                 *      Somebody is trying to suspend the thread.
        !           264:                 */
        !           265: 
        !           266:                old->state = TH_WAIT|TH_SUSP|TH_SWAPPED;
        !           267:                if (old->wake_active) {
        !           268:                        /*
        !           269:                         *      Someone wants to know when the thread
        !           270:                         *      really stops.
        !           271:                         */
        !           272:                        old->wake_active = FALSE;
        !           273:                        thread_unlock(old);
        !           274:                        thread_wakeup((event_t)&old->wake_active);
        !           275:                        goto after_old_thread;
        !           276:                }
        !           277:        } else
        !           278:                panic("thread_handoff");
        !           279: 
        !           280:        thread_unlock(old);
        !           281:     after_old_thread:
        !           282:        (void) splx(s);
        !           283: 
        !           284:        counter_always(c_thread_handoff_hits++);
        !           285:        return TRUE;
        !           286: }
        !           287: #endif /* CONTINUATIONS */

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