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

1.1     ! root        1: /*
        !             2:  * Mach Operating System
        !             3:  * Copyright (c) 1991,1990,1989,1988,1987 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:  *
        !            28:  *     File:   kern/thread_swap.c
        !            29:  *     Author: Avadis Tevanian, Jr.
        !            30:  *     Date:   1987
        !            31:  *
        !            32:  *     Mach thread swapper:
        !            33:  *             Find idle threads to swap, freeing up kernel stack resources
        !            34:  *             at the expense of allowing them to execute.
        !            35:  *
        !            36:  *             Swap in threads that need to be run.  This is done here
        !            37:  *             by the swapper thread since it cannot be done (in general)
        !            38:  *             when the kernel tries to place a thread on a run queue.
        !            39:  *
        !            40:  *     Note: The act of swapping a thread in Mach does not mean that
        !            41:  *     its memory gets forcibly swapped to secondary storage.  The memory
        !            42:  *     for the task corresponding to a swapped thread is paged out
        !            43:  *     through the normal paging mechanism.
        !            44:  *
        !            45:  */
        !            46: 
        !            47: #include <ipc/ipc_kmsg.h>
        !            48: #include <kern/counters.h>
        !            49: #include <kern/thread.h>
        !            50: #include <kern/lock.h>
        !            51: #include <vm/vm_map.h>
        !            52: #include <vm/vm_kern.h>
        !            53: #include <mach/vm_param.h>
        !            54: #include <kern/sched_prim.h>
        !            55: #include <kern/processor.h>
        !            56: #include <kern/thread_swap.h>
        !            57: #include <machine/machspl.h>           /* for splsched */
        !            58: 
        !            59: 
        !            60: 
        !            61: queue_head_t           swapin_queue;
        !            62: decl_simple_lock_data(,        swapper_lock_data)
        !            63: 
        !            64: #define swapper_lock()         simple_lock(&swapper_lock_data)
        !            65: #define swapper_unlock()       simple_unlock(&swapper_lock_data)
        !            66: 
        !            67: /*
        !            68:  *     swapper_init: [exported]
        !            69:  *
        !            70:  *     Initialize the swapper module.
        !            71:  */
        !            72: void swapper_init()
        !            73: {
        !            74:        queue_init(&swapin_queue);
        !            75:        simple_lock_init(&swapper_lock_data);
        !            76: }
        !            77: 
        !            78: /*
        !            79:  *     thread_swapin: [exported]
        !            80:  *
        !            81:  *     Place the specified thread in the list of threads to swapin.  It
        !            82:  *     is assumed that the thread is locked, therefore we are at splsched.
        !            83:  *
        !            84:  *     We don't bother with stack_alloc_try to optimize swapin;
        !            85:  *     our callers have already tried that route.
        !            86:  */
        !            87: 
        !            88: void thread_swapin(thread)
        !            89:        thread_t        thread;
        !            90: {
        !            91:        switch (thread->state & TH_SWAP_STATE) {
        !            92:            case TH_SWAPPED:
        !            93:                /*
        !            94:                 *      Swapped out - queue for swapin thread.
        !            95:                 */
        !            96:                thread->state = (thread->state & ~TH_SWAP_STATE)
        !            97:                                | TH_SW_COMING_IN;
        !            98:                swapper_lock();
        !            99:                enqueue_tail(&swapin_queue, (queue_entry_t) thread);
        !           100:                swapper_unlock();
        !           101:                thread_wakeup((event_t) &swapin_queue);
        !           102:                break;
        !           103: 
        !           104:            case TH_SW_COMING_IN:
        !           105:                /*
        !           106:                 *      Already queued for swapin thread, or being
        !           107:                 *      swapped in.
        !           108:                 */
        !           109:                break;
        !           110: 
        !           111:            default:
        !           112:                /*
        !           113:                 *      Already swapped in.
        !           114:                 */
        !           115:                panic("thread_swapin");
        !           116:        }
        !           117: }
        !           118: 
        !           119: /*
        !           120:  *     thread_doswapin:
        !           121:  *
        !           122:  *     Swapin the specified thread, if it should be runnable, then put
        !           123:  *     it on a run queue.  No locks should be held on entry, as it is
        !           124:  *     likely that this routine will sleep (waiting for stack allocation).
        !           125:  */
        !           126: void thread_doswapin(thread)
        !           127:        register thread_t thread;
        !           128: {
        !           129:        spl_t   s;
        !           130: 
        !           131:        /*
        !           132:         *      Allocate the kernel stack.
        !           133:         */
        !           134: 
        !           135:        stack_alloc(thread, thread_continue);
        !           136: 
        !           137:        /*
        !           138:         *      Place on run queue.  
        !           139:         */
        !           140: 
        !           141:        s = splsched();
        !           142:        thread_lock(thread);
        !           143:        thread->state &= ~(TH_SWAPPED | TH_SW_COMING_IN);
        !           144:        if (thread->state & TH_RUN)
        !           145:                thread_setrun(thread, TRUE);
        !           146:        thread_unlock(thread);
        !           147:        (void) splx(s);
        !           148: }
        !           149: 
        !           150: /*
        !           151:  *     swapin_thread: [exported]
        !           152:  *
        !           153:  *     This procedure executes as a kernel thread.  Threads that need to
        !           154:  *     be swapped in are swapped in by this thread.
        !           155:  */
        !           156: void swapin_thread_continue()
        !           157: {
        !           158:        for (;;) {
        !           159:                register thread_t thread;
        !           160:                spl_t s;
        !           161: 
        !           162:                s = splsched();
        !           163:                swapper_lock();
        !           164: 
        !           165:                while ((thread = (thread_t) dequeue_head(&swapin_queue))
        !           166:                                                        != THREAD_NULL) {
        !           167:                        swapper_unlock();
        !           168:                        (void) splx(s);
        !           169: 
        !           170:                        thread_doswapin(thread);                /* may block */
        !           171: 
        !           172:                        s = splsched();
        !           173:                        swapper_lock();
        !           174:                }
        !           175: 
        !           176:                assert_wait((event_t) &swapin_queue, FALSE);
        !           177:                swapper_unlock();
        !           178:                (void) splx(s);
        !           179:                counter(c_swapin_thread_block++);
        !           180:                thread_block(swapin_thread_continue);
        !           181:        }
        !           182: }
        !           183: 
        !           184: void swapin_thread()
        !           185: {
        !           186:        stack_privilege(current_thread());
        !           187: 
        !           188:        swapin_thread_continue();
        !           189:        /*NOTREACHED*/
        !           190: }

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