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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
 
1248 jermar 29
/**
30
 * @file    waitq.c
31
 * @brief   Wait queue.
32
 *
1288 jermar 33
 * Wait queue is the basic synchronization primitive upon which all
1248 jermar 34
 * other synchronization primitives build.
35
 *
36
 * It allows threads to wait for an event in first-come, first-served
37
 * fashion. Conditional operation as well as timeouts and interruptions
38
 * are supported.
39
 */
40
 
382 jermar 41
#include <synch/waitq.h>
1 jermar 42
#include <synch/synch.h>
43
#include <synch/spinlock.h>
382 jermar 44
#include <proc/thread.h>
414 jermar 45
#include <proc/scheduler.h>
1 jermar 46
#include <arch/asm.h>
47
#include <arch/types.h>
557 jermar 48
#include <typedefs.h>
382 jermar 49
#include <time/timeout.h>
1 jermar 50
#include <arch.h>
382 jermar 51
#include <context.h>
788 jermar 52
#include <adt/list.h>
1 jermar 53
 
1156 jermar 54
static void waitq_timeouted_sleep(void *data);
55
 
382 jermar 56
/** Initialize wait queue
57
 *
58
 * Initialize wait queue.
59
 *
60
 * @param wq Pointer to wait queue to be initialized.
61
 */
1 jermar 62
void waitq_initialize(waitq_t *wq)
63
{
552 palkovsky 64
    spinlock_initialize(&wq->lock, "waitq_lock");
1 jermar 65
    list_initialize(&wq->head);
66
    wq->missed_wakeups = 0;
67
}
68
 
382 jermar 69
/** Handle timeout during waitq_sleep_timeout() call
1 jermar 70
 *
382 jermar 71
 * This routine is called when waitq_sleep_timeout() timeouts.
72
 * Interrupts are disabled.
73
 *
74
 * It is supposed to try to remove 'its' thread from the wait queue;
75
 * it can eventually fail to achieve this goal when these two events
76
 * overlap. In that case it behaves just as though there was no
77
 * timeout at all.
78
 *
79
 * @param data Pointer to the thread that called waitq_sleep_timeout().
1 jermar 80
 */
1156 jermar 81
void waitq_timeouted_sleep(void *data)
1 jermar 82
{
83
    thread_t *t = (thread_t *) data;
84
    waitq_t *wq;
557 jermar 85
    bool do_wakeup = false;
1 jermar 86
 
87
    spinlock_lock(&threads_lock);
1158 jermar 88
    if (!thread_exists(t))
1 jermar 89
        goto out;
90
 
91
grab_locks:
92
    spinlock_lock(&t->lock);
615 palkovsky 93
    if ((wq = t->sleep_queue)) {        /* assignment */
1 jermar 94
        if (!spinlock_trylock(&wq->lock)) {
95
            spinlock_unlock(&t->lock);
557 jermar 96
            goto grab_locks;    /* avoid deadlock */
1 jermar 97
        }
98
 
99
        list_remove(&t->wq_link);
100
        t->saved_context = t->sleep_timeout_context;
557 jermar 101
        do_wakeup = true;
1 jermar 102
 
103
        spinlock_unlock(&wq->lock);
104
        t->sleep_queue = NULL;
105
    }
106
 
557 jermar 107
    t->timeout_pending = false;
1 jermar 108
    spinlock_unlock(&t->lock);
109
 
557 jermar 110
    if (do_wakeup)
111
        thread_ready(t);
1 jermar 112
 
113
out:
114
    spinlock_unlock(&threads_lock);
115
}
116
 
1156 jermar 117
/** Interrupt sleeping thread.
382 jermar 118
 *
1156 jermar 119
 * This routine attempts to interrupt a thread from its sleep in a waitqueue.
120
 * If the thread is not found sleeping, no action is taken.
121
 *
122
 * @param t Thread to be interrupted.
123
 */
124
void waitq_interrupt_sleep(thread_t *t)
125
{
126
    waitq_t *wq;
127
    bool do_wakeup = false;
128
    ipl_t ipl;
129
 
130
    ipl = interrupts_disable();
131
    spinlock_lock(&threads_lock);
1158 jermar 132
    if (!thread_exists(t))
1156 jermar 133
        goto out;
134
 
135
grab_locks:
136
    spinlock_lock(&t->lock);
137
    if ((wq = t->sleep_queue)) {        /* assignment */
1502 jermar 138
        if (!(t->sleep_interruptible)) {
139
            /*
140
             * The sleep cannot be interrupted.
141
             */
142
            spinlock_unlock(&t->lock);
143
            goto out;
144
        }
145
 
1156 jermar 146
        if (!spinlock_trylock(&wq->lock)) {
147
            spinlock_unlock(&t->lock);
148
            goto grab_locks;    /* avoid deadlock */
149
        }
150
 
151
        list_remove(&t->wq_link);
152
        t->saved_context = t->sleep_interruption_context;
153
        do_wakeup = true;
154
 
155
        spinlock_unlock(&wq->lock);
156
        t->sleep_queue = NULL;
157
    }
158
    spinlock_unlock(&t->lock);
159
 
160
    if (do_wakeup)
161
        thread_ready(t);
162
 
163
out:
164
    spinlock_unlock(&threads_lock);
165
    interrupts_restore(ipl);
166
}
167
 
168
/** Sleep until either wakeup, timeout or interruption occurs
169
 *
1502 jermar 170
 * This is a sleep implementation which allows itself to time out or to be
1 jermar 171
 * interrupted from the sleep, restoring a failover context.
172
 *
1375 jermar 173
 * Sleepers are organised in a FIFO fashion in a structure called wait queue.
382 jermar 174
 *
1 jermar 175
 * This function is really basic in that other functions as waitq_sleep()
176
 * and all the *_timeout() functions use it.
177
 *
382 jermar 178
 * @param wq Pointer to wait queue.
404 jermar 179
 * @param usec Timeout in microseconds.
1502 jermar 180
 * @param flags Specify mode of the sleep.
1 jermar 181
 *
1502 jermar 182
 * The sleep can be interrupted only if the
183
 * SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
184
 
185
 * If usec is greater than zero, regardless of the value of the
186
 * SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout,
187
 * interruption or wakeup comes.
382 jermar 188
 *
1502 jermar 189
 * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call
190
 * will not return until wakeup or interruption comes.
1 jermar 191
 *
1502 jermar 192
 * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will
404 jermar 193
 * immediately return, reporting either success or failure.
194
 *
1502 jermar 195
 * @return  Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
1248 jermar 196
 *          ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
382 jermar 197
 *
1248 jermar 198
 * @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
404 jermar 199
 * of the call there was no pending wakeup.
382 jermar 200
 *
1248 jermar 201
 * @li ESYNCH_TIMEOUT means that the sleep timed out.
404 jermar 202
 *
1248 jermar 203
 * @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
1156 jermar 204
 *
1248 jermar 205
 * @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
404 jermar 206
 * a pending wakeup at the time of the call. The caller was not put
207
 * asleep at all.
208
 *
1248 jermar 209
 * @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
404 jermar 210
 * attempted.
1 jermar 211
 */
1502 jermar 212
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)
1 jermar 213
{
1375 jermar 214
    ipl_t ipl;
215
    int rc;
1 jermar 216
 
1375 jermar 217
    ipl = waitq_sleep_prepare(wq);
1502 jermar 218
    rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
1375 jermar 219
    waitq_sleep_finish(wq, rc, ipl);
220
    return rc;
221
}
222
 
223
/** Prepare to sleep in a waitq.
224
 *
225
 * This function will return holding the lock of the wait queue
226
 * and interrupts disabled.
227
 *
228
 * @param wq Wait queue.
229
 *
230
 * @return Interrupt level as it existed on entry to this function.
231
 */
232
ipl_t waitq_sleep_prepare(waitq_t *wq)
233
{
234
    ipl_t ipl;
1 jermar 235
 
236
restart:
413 jermar 237
    ipl = interrupts_disable();
1375 jermar 238
 
1467 jermar 239
    if (THREAD) {   /* needed during system initiailzation */
240
        /*
241
         * Busy waiting for a delayed timeout.
242
         * This is an important fix for the race condition between
243
         * a delayed timeout and a next call to waitq_sleep_timeout().
244
         * Simply, the thread is not allowed to go to sleep if
245
         * there are timeouts in progress.
246
         */
247
        spinlock_lock(&THREAD->lock);
248
        if (THREAD->timeout_pending) {
249
            spinlock_unlock(&THREAD->lock);
250
            interrupts_restore(ipl);
251
            goto restart;
252
        }
15 jermar 253
        spinlock_unlock(&THREAD->lock);
1 jermar 254
    }
1375 jermar 255
 
1 jermar 256
    spinlock_lock(&wq->lock);
1375 jermar 257
    return ipl;
258
}
259
 
260
/** Finish waiting in a wait queue.
261
 *
262
 * This function restores interrupts to the state that existed prior
263
 * to the call to waitq_sleep_prepare(). If necessary, the wait queue
264
 * lock is released.
265
 *
266
 * @param wq Wait queue.
267
 * @param rc Return code of waitq_sleep_timeout_unsafe().
268
 * @param ipl Interrupt level returned by waitq_sleep_prepare().
269
 */
270
void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
271
{
272
    switch (rc) {
273
    case ESYNCH_WOULD_BLOCK:
274
    case ESYNCH_OK_ATOMIC:
275
        spinlock_unlock(&wq->lock);
276
        break;
277
    default:
278
        break;
279
    }
280
    interrupts_restore(ipl);
281
}
282
 
283
/** Internal implementation of waitq_sleep_timeout().
284
 *
285
 * This function implements logic of sleeping in a wait queue.
286
 * This call must be preceeded by a call to waitq_sleep_prepare()
287
 * and followed by a call to waitq_slee_finish().
288
 *
289
 * @param wq See waitq_sleep_timeout().
290
 * @param usec See waitq_sleep_timeout().
1502 jermar 291
 * @param flags See waitq_sleep_timeout().
1375 jermar 292
 *
293
 * @return See waitq_sleep_timeout().
294
 */
1502 jermar 295
int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)
1375 jermar 296
{
1 jermar 297
    /* checks whether to go to sleep at all */
298
    if (wq->missed_wakeups) {
299
        wq->missed_wakeups--;
300
        return ESYNCH_OK_ATOMIC;
301
    }
302
    else {
1502 jermar 303
        if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
1 jermar 304
            /* return immediatelly instead of going to sleep */
305
            return ESYNCH_WOULD_BLOCK;
306
        }
307
    }
308
 
309
    /*
310
     * Now we are firmly decided to go to sleep.
311
     */
15 jermar 312
    spinlock_lock(&THREAD->lock);
1156 jermar 313
 
1580 jermar 314
    if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
1579 jermar 315
 
1502 jermar 316
        /*
1580 jermar 317
         * If the thread was already interrupted,
318
         * don't go to sleep at all.
319
         */
320
        if (THREAD->interrupted) {
321
            spinlock_unlock(&THREAD->lock);
322
            spinlock_unlock(&wq->lock);
323
            return ESYNCH_INTERRUPTED;
324
        }
325
 
326
        /*
1502 jermar 327
         * Set context that will be restored if the sleep
328
         * of this thread is ever interrupted.
329
         */
330
        THREAD->sleep_interruptible = true;
331
        if (!context_save(&THREAD->sleep_interruption_context)) {
332
            /* Short emulation of scheduler() return code. */
333
            spinlock_unlock(&THREAD->lock);
334
            return ESYNCH_INTERRUPTED;
335
        }
1580 jermar 336
 
1502 jermar 337
    } else {
338
        THREAD->sleep_interruptible = false;
1156 jermar 339
    }
340
 
1 jermar 341
    if (usec) {
342
        /* We use the timeout variant. */
15 jermar 343
        if (!context_save(&THREAD->sleep_timeout_context)) {
1156 jermar 344
            /* Short emulation of scheduler() return code. */
15 jermar 345
            spinlock_unlock(&THREAD->lock);
1 jermar 346
            return ESYNCH_TIMEOUT;
347
        }
557 jermar 348
        THREAD->timeout_pending = true;
1156 jermar 349
        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
1 jermar 350
    }
351
 
15 jermar 352
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 353
 
354
    /*
355
     * Suspend execution.
356
     */
15 jermar 357
    THREAD->state = Sleeping;
358
    THREAD->sleep_queue = wq;
1 jermar 359
 
15 jermar 360
    spinlock_unlock(&THREAD->lock);
1 jermar 361
 
362
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
363
 
364
    return ESYNCH_OK_BLOCKED;
365
}
366
 
367
 
382 jermar 368
/** Wake up first thread sleeping in a wait queue
369
 *
370
 * Wake up first thread sleeping in a wait queue.
371
 * This is the SMP- and IRQ-safe wrapper meant for
372
 * general use.
373
 *
374
 * Besides its 'normal' wakeup operation, it attempts
375
 * to unregister possible timeout.
376
 *
377
 * @param wq Pointer to wait queue.
378
 * @param all If this is non-zero, all sleeping threads
379
 *        will be woken up and missed count will be zeroed.
1 jermar 380
 */
557 jermar 381
void waitq_wakeup(waitq_t *wq, bool all)
1 jermar 382
{
413 jermar 383
    ipl_t ipl;
1 jermar 384
 
413 jermar 385
    ipl = interrupts_disable();
1 jermar 386
    spinlock_lock(&wq->lock);
387
 
388
    _waitq_wakeup_unsafe(wq, all);
389
 
390
    spinlock_unlock(&wq->lock);
413 jermar 391
    interrupts_restore(ipl);   
1 jermar 392
}
393
 
382 jermar 394
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
395
 *
396
 * This is the internal SMP- and IRQ-unsafe version
397
 * of waitq_wakeup(). It assumes wq->lock is already
398
 * locked and interrupts are already disabled.
399
 *
400
 * @param wq Pointer to wait queue.
401
 * @param all If this is non-zero, all sleeping threads
402
 *        will be woken up and missed count will be zeroed.
1 jermar 403
 */
557 jermar 404
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
1 jermar 405
{
406
    thread_t *t;
407
 
408
loop:  
409
    if (list_empty(&wq->head)) {
410
        wq->missed_wakeups++;
557 jermar 411
        if (all)
412
            wq->missed_wakeups = 0;
1 jermar 413
        return;
414
    }
415
 
416
    t = list_get_instance(wq->head.next, thread_t, wq_link);
417
 
418
    list_remove(&t->wq_link);
419
    spinlock_lock(&t->lock);
420
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
557 jermar 421
        t->timeout_pending = false;
1 jermar 422
    t->sleep_queue = NULL;
423
    spinlock_unlock(&t->lock);
424
 
425
    thread_ready(t);
426
 
557 jermar 427
    if (all)
428
        goto loop;
1 jermar 429
}