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1 jermar 1
/*
2
 * Copyright (C) 2001-2004 Jakub Jermar
3
 * All rights reserved.
4
 *
5
 * Redistribution and use in source and binary forms, with or without
6
 * modification, are permitted provided that the following conditions
7
 * are met:
8
 *
9
 * - Redistributions of source code must retain the above copyright
10
 *   notice, this list of conditions and the following disclaimer.
11
 * - Redistributions in binary form must reproduce the above copyright
12
 *   notice, this list of conditions and the following disclaimer in the
13
 *   documentation and/or other materials provided with the distribution.
14
 * - The name of the author may not be used to endorse or promote products
15
 *   derived from this software without specific prior written permission.
16
 *
17
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
 */
28
 
1702 cejka 29
 /** @addtogroup sync
30
 * @{
31
 */
32
 
1248 jermar 33
/**
1702 cejka 34
 * @file
1248 jermar 35
 * @brief   Wait queue.
36
 *
1288 jermar 37
 * Wait queue is the basic synchronization primitive upon which all
1248 jermar 38
 * other synchronization primitives build.
39
 *
40
 * It allows threads to wait for an event in first-come, first-served
41
 * fashion. Conditional operation as well as timeouts and interruptions
42
 * are supported.
43
 */
44
 
382 jermar 45
#include <synch/waitq.h>
1 jermar 46
#include <synch/synch.h>
47
#include <synch/spinlock.h>
382 jermar 48
#include <proc/thread.h>
414 jermar 49
#include <proc/scheduler.h>
1 jermar 50
#include <arch/asm.h>
51
#include <arch/types.h>
557 jermar 52
#include <typedefs.h>
382 jermar 53
#include <time/timeout.h>
1 jermar 54
#include <arch.h>
382 jermar 55
#include <context.h>
788 jermar 56
#include <adt/list.h>
1 jermar 57
 
1156 jermar 58
static void waitq_timeouted_sleep(void *data);
59
 
382 jermar 60
/** Initialize wait queue
61
 *
62
 * Initialize wait queue.
63
 *
64
 * @param wq Pointer to wait queue to be initialized.
65
 */
1 jermar 66
void waitq_initialize(waitq_t *wq)
67
{
552 palkovsky 68
    spinlock_initialize(&wq->lock, "waitq_lock");
1 jermar 69
    list_initialize(&wq->head);
70
    wq->missed_wakeups = 0;
71
}
72
 
382 jermar 73
/** Handle timeout during waitq_sleep_timeout() call
1 jermar 74
 *
382 jermar 75
 * This routine is called when waitq_sleep_timeout() timeouts.
76
 * Interrupts are disabled.
77
 *
78
 * It is supposed to try to remove 'its' thread from the wait queue;
79
 * it can eventually fail to achieve this goal when these two events
80
 * overlap. In that case it behaves just as though there was no
81
 * timeout at all.
82
 *
83
 * @param data Pointer to the thread that called waitq_sleep_timeout().
1 jermar 84
 */
1156 jermar 85
void waitq_timeouted_sleep(void *data)
1 jermar 86
{
87
    thread_t *t = (thread_t *) data;
88
    waitq_t *wq;
557 jermar 89
    bool do_wakeup = false;
1 jermar 90
 
91
    spinlock_lock(&threads_lock);
1158 jermar 92
    if (!thread_exists(t))
1 jermar 93
        goto out;
94
 
95
grab_locks:
96
    spinlock_lock(&t->lock);
615 palkovsky 97
    if ((wq = t->sleep_queue)) {        /* assignment */
1 jermar 98
        if (!spinlock_trylock(&wq->lock)) {
99
            spinlock_unlock(&t->lock);
557 jermar 100
            goto grab_locks;    /* avoid deadlock */
1 jermar 101
        }
102
 
103
        list_remove(&t->wq_link);
104
        t->saved_context = t->sleep_timeout_context;
557 jermar 105
        do_wakeup = true;
1681 jermar 106
        t->sleep_queue = NULL;
1 jermar 107
        spinlock_unlock(&wq->lock);
108
    }
109
 
557 jermar 110
    t->timeout_pending = false;
1 jermar 111
    spinlock_unlock(&t->lock);
112
 
557 jermar 113
    if (do_wakeup)
114
        thread_ready(t);
1 jermar 115
 
116
out:
117
    spinlock_unlock(&threads_lock);
118
}
119
 
1156 jermar 120
/** Interrupt sleeping thread.
382 jermar 121
 *
1156 jermar 122
 * This routine attempts to interrupt a thread from its sleep in a waitqueue.
123
 * If the thread is not found sleeping, no action is taken.
124
 *
125
 * @param t Thread to be interrupted.
126
 */
127
void waitq_interrupt_sleep(thread_t *t)
128
{
129
    waitq_t *wq;
130
    bool do_wakeup = false;
131
    ipl_t ipl;
132
 
133
    ipl = interrupts_disable();
134
    spinlock_lock(&threads_lock);
1158 jermar 135
    if (!thread_exists(t))
1156 jermar 136
        goto out;
137
 
138
grab_locks:
139
    spinlock_lock(&t->lock);
140
    if ((wq = t->sleep_queue)) {        /* assignment */
1502 jermar 141
        if (!(t->sleep_interruptible)) {
142
            /*
143
             * The sleep cannot be interrupted.
144
             */
145
            spinlock_unlock(&t->lock);
146
            goto out;
147
        }
148
 
1156 jermar 149
        if (!spinlock_trylock(&wq->lock)) {
150
            spinlock_unlock(&t->lock);
151
            goto grab_locks;    /* avoid deadlock */
152
        }
153
 
1593 jermar 154
        if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
155
            t->timeout_pending = false;
156
 
1156 jermar 157
        list_remove(&t->wq_link);
158
        t->saved_context = t->sleep_interruption_context;
159
        do_wakeup = true;
1681 jermar 160
        t->sleep_queue = NULL;
1156 jermar 161
        spinlock_unlock(&wq->lock);
162
    }
163
    spinlock_unlock(&t->lock);
164
 
165
    if (do_wakeup)
166
        thread_ready(t);
167
 
168
out:
169
    spinlock_unlock(&threads_lock);
170
    interrupts_restore(ipl);
171
}
172
 
173
/** Sleep until either wakeup, timeout or interruption occurs
174
 *
1502 jermar 175
 * This is a sleep implementation which allows itself to time out or to be
1 jermar 176
 * interrupted from the sleep, restoring a failover context.
177
 *
1375 jermar 178
 * Sleepers are organised in a FIFO fashion in a structure called wait queue.
382 jermar 179
 *
1 jermar 180
 * This function is really basic in that other functions as waitq_sleep()
181
 * and all the *_timeout() functions use it.
182
 *
382 jermar 183
 * @param wq Pointer to wait queue.
404 jermar 184
 * @param usec Timeout in microseconds.
1502 jermar 185
 * @param flags Specify mode of the sleep.
1 jermar 186
 *
1502 jermar 187
 * The sleep can be interrupted only if the
188
 * SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
189
 
190
 * If usec is greater than zero, regardless of the value of the
191
 * SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout,
192
 * interruption or wakeup comes.
382 jermar 193
 *
1502 jermar 194
 * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call
195
 * will not return until wakeup or interruption comes.
1 jermar 196
 *
1502 jermar 197
 * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will
404 jermar 198
 * immediately return, reporting either success or failure.
199
 *
1502 jermar 200
 * @return  Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
1248 jermar 201
 *          ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
382 jermar 202
 *
1248 jermar 203
 * @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
404 jermar 204
 * of the call there was no pending wakeup.
382 jermar 205
 *
1248 jermar 206
 * @li ESYNCH_TIMEOUT means that the sleep timed out.
404 jermar 207
 *
1248 jermar 208
 * @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
1156 jermar 209
 *
1248 jermar 210
 * @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
404 jermar 211
 * a pending wakeup at the time of the call. The caller was not put
212
 * asleep at all.
213
 *
1248 jermar 214
 * @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
404 jermar 215
 * attempted.
1 jermar 216
 */
1502 jermar 217
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)
1 jermar 218
{
1375 jermar 219
    ipl_t ipl;
220
    int rc;
1 jermar 221
 
1375 jermar 222
    ipl = waitq_sleep_prepare(wq);
1502 jermar 223
    rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
1375 jermar 224
    waitq_sleep_finish(wq, rc, ipl);
225
    return rc;
226
}
227
 
228
/** Prepare to sleep in a waitq.
229
 *
230
 * This function will return holding the lock of the wait queue
231
 * and interrupts disabled.
232
 *
233
 * @param wq Wait queue.
234
 *
235
 * @return Interrupt level as it existed on entry to this function.
236
 */
237
ipl_t waitq_sleep_prepare(waitq_t *wq)
238
{
239
    ipl_t ipl;
1 jermar 240
 
241
restart:
413 jermar 242
    ipl = interrupts_disable();
1375 jermar 243
 
1467 jermar 244
    if (THREAD) {   /* needed during system initiailzation */
245
        /*
246
         * Busy waiting for a delayed timeout.
247
         * This is an important fix for the race condition between
248
         * a delayed timeout and a next call to waitq_sleep_timeout().
249
         * Simply, the thread is not allowed to go to sleep if
250
         * there are timeouts in progress.
251
         */
252
        spinlock_lock(&THREAD->lock);
253
        if (THREAD->timeout_pending) {
254
            spinlock_unlock(&THREAD->lock);
255
            interrupts_restore(ipl);
256
            goto restart;
257
        }
15 jermar 258
        spinlock_unlock(&THREAD->lock);
1 jermar 259
    }
1375 jermar 260
 
1 jermar 261
    spinlock_lock(&wq->lock);
1375 jermar 262
    return ipl;
263
}
264
 
265
/** Finish waiting in a wait queue.
266
 *
267
 * This function restores interrupts to the state that existed prior
268
 * to the call to waitq_sleep_prepare(). If necessary, the wait queue
269
 * lock is released.
270
 *
271
 * @param wq Wait queue.
272
 * @param rc Return code of waitq_sleep_timeout_unsafe().
273
 * @param ipl Interrupt level returned by waitq_sleep_prepare().
274
 */
275
void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
276
{
277
    switch (rc) {
278
    case ESYNCH_WOULD_BLOCK:
279
    case ESYNCH_OK_ATOMIC:
280
        spinlock_unlock(&wq->lock);
281
        break;
282
    default:
283
        break;
284
    }
285
    interrupts_restore(ipl);
286
}
287
 
288
/** Internal implementation of waitq_sleep_timeout().
289
 *
290
 * This function implements logic of sleeping in a wait queue.
291
 * This call must be preceeded by a call to waitq_sleep_prepare()
292
 * and followed by a call to waitq_slee_finish().
293
 *
294
 * @param wq See waitq_sleep_timeout().
295
 * @param usec See waitq_sleep_timeout().
1502 jermar 296
 * @param flags See waitq_sleep_timeout().
1375 jermar 297
 *
298
 * @return See waitq_sleep_timeout().
299
 */
1502 jermar 300
int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)
1375 jermar 301
{
1 jermar 302
    /* checks whether to go to sleep at all */
303
    if (wq->missed_wakeups) {
304
        wq->missed_wakeups--;
305
        return ESYNCH_OK_ATOMIC;
306
    }
307
    else {
1502 jermar 308
        if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
1 jermar 309
            /* return immediatelly instead of going to sleep */
310
            return ESYNCH_WOULD_BLOCK;
311
        }
312
    }
313
 
314
    /*
315
     * Now we are firmly decided to go to sleep.
316
     */
15 jermar 317
    spinlock_lock(&THREAD->lock);
1156 jermar 318
 
1580 jermar 319
    if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
1579 jermar 320
 
1502 jermar 321
        /*
1580 jermar 322
         * If the thread was already interrupted,
323
         * don't go to sleep at all.
324
         */
325
        if (THREAD->interrupted) {
326
            spinlock_unlock(&THREAD->lock);
327
            spinlock_unlock(&wq->lock);
328
            return ESYNCH_INTERRUPTED;
329
        }
330
 
331
        /*
1502 jermar 332
         * Set context that will be restored if the sleep
333
         * of this thread is ever interrupted.
334
         */
335
        THREAD->sleep_interruptible = true;
336
        if (!context_save(&THREAD->sleep_interruption_context)) {
337
            /* Short emulation of scheduler() return code. */
338
            spinlock_unlock(&THREAD->lock);
339
            return ESYNCH_INTERRUPTED;
340
        }
1580 jermar 341
 
1502 jermar 342
    } else {
343
        THREAD->sleep_interruptible = false;
1156 jermar 344
    }
345
 
1 jermar 346
    if (usec) {
347
        /* We use the timeout variant. */
15 jermar 348
        if (!context_save(&THREAD->sleep_timeout_context)) {
1156 jermar 349
            /* Short emulation of scheduler() return code. */
15 jermar 350
            spinlock_unlock(&THREAD->lock);
1 jermar 351
            return ESYNCH_TIMEOUT;
352
        }
557 jermar 353
        THREAD->timeout_pending = true;
1156 jermar 354
        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
1 jermar 355
    }
356
 
15 jermar 357
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 358
 
359
    /*
360
     * Suspend execution.
361
     */
15 jermar 362
    THREAD->state = Sleeping;
363
    THREAD->sleep_queue = wq;
1 jermar 364
 
15 jermar 365
    spinlock_unlock(&THREAD->lock);
1 jermar 366
 
367
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
368
 
369
    return ESYNCH_OK_BLOCKED;
370
}
371
 
372
 
382 jermar 373
/** Wake up first thread sleeping in a wait queue
374
 *
375
 * Wake up first thread sleeping in a wait queue.
376
 * This is the SMP- and IRQ-safe wrapper meant for
377
 * general use.
378
 *
379
 * Besides its 'normal' wakeup operation, it attempts
380
 * to unregister possible timeout.
381
 *
382
 * @param wq Pointer to wait queue.
383
 * @param all If this is non-zero, all sleeping threads
384
 *        will be woken up and missed count will be zeroed.
1 jermar 385
 */
557 jermar 386
void waitq_wakeup(waitq_t *wq, bool all)
1 jermar 387
{
413 jermar 388
    ipl_t ipl;
1 jermar 389
 
413 jermar 390
    ipl = interrupts_disable();
1 jermar 391
    spinlock_lock(&wq->lock);
392
 
393
    _waitq_wakeup_unsafe(wq, all);
394
 
395
    spinlock_unlock(&wq->lock);
413 jermar 396
    interrupts_restore(ipl);   
1 jermar 397
}
398
 
382 jermar 399
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
400
 *
401
 * This is the internal SMP- and IRQ-unsafe version
402
 * of waitq_wakeup(). It assumes wq->lock is already
403
 * locked and interrupts are already disabled.
404
 *
405
 * @param wq Pointer to wait queue.
406
 * @param all If this is non-zero, all sleeping threads
407
 *        will be woken up and missed count will be zeroed.
1 jermar 408
 */
557 jermar 409
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
1 jermar 410
{
411
    thread_t *t;
412
 
413
loop:  
414
    if (list_empty(&wq->head)) {
415
        wq->missed_wakeups++;
557 jermar 416
        if (all)
417
            wq->missed_wakeups = 0;
1 jermar 418
        return;
419
    }
420
 
421
    t = list_get_instance(wq->head.next, thread_t, wq_link);
422
 
1681 jermar 423
    /*
424
     * Lock the thread prior to removing it from the wq.
425
     * This is not necessary because of mutual exclusion
426
     * (the link belongs to the wait queue), but because
427
     * of synchronization with waitq_timeouted_sleep()
428
     * and waitq_interrupt_sleep().
429
     *
430
     * In order for these two functions to work, the following
431
     * invariant must hold:
432
     *
433
     * t->sleep_queue != NULL <=> t sleeps in a wait queue
434
     *
435
     * For an observer who locks the thread, the invariant
436
     * holds only when the lock is held prior to removing
437
     * it from the wait queue.
438
     */
439
    spinlock_lock(&t->lock);
1 jermar 440
    list_remove(&t->wq_link);
1681 jermar 441
 
1 jermar 442
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
557 jermar 443
        t->timeout_pending = false;
1 jermar 444
    t->sleep_queue = NULL;
445
    spinlock_unlock(&t->lock);
446
 
447
    thread_ready(t);
448
 
557 jermar 449
    if (all)
450
        goto loop;
1 jermar 451
}
1702 cejka 452
 
453
 /** @}
454
 */
455