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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 */
138
        if (!spinlock_trylock(&wq->lock)) {
139
            spinlock_unlock(&t->lock);
140
            goto grab_locks;    /* avoid deadlock */
141
        }
142
 
143
        list_remove(&t->wq_link);
144
        t->saved_context = t->sleep_interruption_context;
145
        do_wakeup = true;
146
 
147
        spinlock_unlock(&wq->lock);
148
        t->sleep_queue = NULL;
149
    }
150
    spinlock_unlock(&t->lock);
151
 
152
    if (do_wakeup)
153
        thread_ready(t);
154
 
155
out:
156
    spinlock_unlock(&threads_lock);
157
    interrupts_restore(ipl);
158
}
159
 
160
/** Sleep until either wakeup, timeout or interruption occurs
161
 *
1 jermar 162
 * This is a sleep implementation which allows itself to be
163
 * interrupted from the sleep, restoring a failover context.
164
 *
1375 jermar 165
 * Sleepers are organised in a FIFO fashion in a structure called wait queue.
382 jermar 166
 *
1 jermar 167
 * This function is really basic in that other functions as waitq_sleep()
168
 * and all the *_timeout() functions use it.
169
 *
382 jermar 170
 * @param wq Pointer to wait queue.
404 jermar 171
 * @param usec Timeout in microseconds.
172
 * @param nonblocking Blocking vs. non-blocking operation mode switch.
1 jermar 173
 *
1248 jermar 174
 * If usec is greater than zero, regardless of the value of nonblocking,
404 jermar 175
 * the call will not return until either timeout or wakeup comes.
382 jermar 176
 *
1248 jermar 177
 * If usec is zero and @nonblocking is zero (false), the call
404 jermar 178
 * will not return until wakeup comes.
1 jermar 179
 *
1248 jermar 180
 * If usec is zero and nonblocking is non-zero (true), the call will
404 jermar 181
 * immediately return, reporting either success or failure.
182
 *
1248 jermar 183
 * @return  Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
184
 *          ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
382 jermar 185
 *
1248 jermar 186
 * @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
404 jermar 187
 * of the call there was no pending wakeup.
382 jermar 188
 *
1248 jermar 189
 * @li ESYNCH_TIMEOUT means that the sleep timed out.
404 jermar 190
 *
1248 jermar 191
 * @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
1156 jermar 192
 *
1248 jermar 193
 * @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
404 jermar 194
 * a pending wakeup at the time of the call. The caller was not put
195
 * asleep at all.
196
 *
1248 jermar 197
 * @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
404 jermar 198
 * attempted.
1 jermar 199
 */
200
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
201
{
1375 jermar 202
    ipl_t ipl;
203
    int rc;
1 jermar 204
 
1375 jermar 205
    ipl = waitq_sleep_prepare(wq);
206
    rc = waitq_sleep_timeout_unsafe(wq, usec, nonblocking);
207
    waitq_sleep_finish(wq, rc, ipl);
208
    return rc;
209
}
210
 
211
/** Prepare to sleep in a waitq.
212
 *
213
 * This function will return holding the lock of the wait queue
214
 * and interrupts disabled.
215
 *
216
 * @param wq Wait queue.
217
 *
218
 * @return Interrupt level as it existed on entry to this function.
219
 */
220
ipl_t waitq_sleep_prepare(waitq_t *wq)
221
{
222
    ipl_t ipl;
1 jermar 223
 
224
restart:
413 jermar 225
    ipl = interrupts_disable();
1375 jermar 226
 
1467 jermar 227
    if (THREAD) {   /* needed during system initiailzation */
228
        /*
229
         * Busy waiting for a delayed timeout.
230
         * This is an important fix for the race condition between
231
         * a delayed timeout and a next call to waitq_sleep_timeout().
232
         * Simply, the thread is not allowed to go to sleep if
233
         * there are timeouts in progress.
234
         */
235
        spinlock_lock(&THREAD->lock);
236
        if (THREAD->timeout_pending) {
237
            spinlock_unlock(&THREAD->lock);
238
            interrupts_restore(ipl);
239
            goto restart;
240
        }
15 jermar 241
        spinlock_unlock(&THREAD->lock);
1 jermar 242
    }
1375 jermar 243
 
1 jermar 244
    spinlock_lock(&wq->lock);
1375 jermar 245
    return ipl;
246
}
247
 
248
/** Finish waiting in a wait queue.
249
 *
250
 * This function restores interrupts to the state that existed prior
251
 * to the call to waitq_sleep_prepare(). If necessary, the wait queue
252
 * lock is released.
253
 *
254
 * @param wq Wait queue.
255
 * @param rc Return code of waitq_sleep_timeout_unsafe().
256
 * @param ipl Interrupt level returned by waitq_sleep_prepare().
257
 */
258
void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
259
{
260
    switch (rc) {
261
    case ESYNCH_WOULD_BLOCK:
262
    case ESYNCH_OK_ATOMIC:
263
        spinlock_unlock(&wq->lock);
264
        break;
265
    default:
266
        break;
267
    }
268
    interrupts_restore(ipl);
269
}
270
 
271
/** Internal implementation of waitq_sleep_timeout().
272
 *
273
 * This function implements logic of sleeping in a wait queue.
274
 * This call must be preceeded by a call to waitq_sleep_prepare()
275
 * and followed by a call to waitq_slee_finish().
276
 *
277
 * @param wq See waitq_sleep_timeout().
278
 * @param usec See waitq_sleep_timeout().
279
 * @param nonblocking See waitq_sleep_timeout().
280
 *
281
 * @return See waitq_sleep_timeout().
282
 */
283
int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int nonblocking)
284
{
1 jermar 285
    /* checks whether to go to sleep at all */
286
    if (wq->missed_wakeups) {
287
        wq->missed_wakeups--;
288
        return ESYNCH_OK_ATOMIC;
289
    }
290
    else {
291
        if (nonblocking && (usec == 0)) {
292
            /* return immediatelly instead of going to sleep */
293
            return ESYNCH_WOULD_BLOCK;
294
        }
295
    }
296
 
297
    /*
298
     * Now we are firmly decided to go to sleep.
299
     */
15 jermar 300
    spinlock_lock(&THREAD->lock);
1156 jermar 301
 
302
    /*
303
     * Set context that will be restored if the sleep
304
     * of this thread is ever interrupted.
305
     */
306
    if (!context_save(&THREAD->sleep_interruption_context)) {
307
        /* Short emulation of scheduler() return code. */
308
        spinlock_unlock(&THREAD->lock);
309
        return ESYNCH_INTERRUPTED;
310
    }
311
 
1 jermar 312
    if (usec) {
313
        /* We use the timeout variant. */
15 jermar 314
        if (!context_save(&THREAD->sleep_timeout_context)) {
1156 jermar 315
            /* Short emulation of scheduler() return code. */
15 jermar 316
            spinlock_unlock(&THREAD->lock);
1 jermar 317
            return ESYNCH_TIMEOUT;
318
        }
557 jermar 319
        THREAD->timeout_pending = true;
1156 jermar 320
        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
1 jermar 321
    }
322
 
15 jermar 323
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 324
 
325
    /*
326
     * Suspend execution.
327
     */
15 jermar 328
    THREAD->state = Sleeping;
329
    THREAD->sleep_queue = wq;
1 jermar 330
 
15 jermar 331
    spinlock_unlock(&THREAD->lock);
1 jermar 332
 
333
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
334
 
335
    return ESYNCH_OK_BLOCKED;
336
}
337
 
338
 
382 jermar 339
/** Wake up first thread sleeping in a wait queue
340
 *
341
 * Wake up first thread sleeping in a wait queue.
342
 * This is the SMP- and IRQ-safe wrapper meant for
343
 * general use.
344
 *
345
 * Besides its 'normal' wakeup operation, it attempts
346
 * to unregister possible timeout.
347
 *
348
 * @param wq Pointer to wait queue.
349
 * @param all If this is non-zero, all sleeping threads
350
 *        will be woken up and missed count will be zeroed.
1 jermar 351
 */
557 jermar 352
void waitq_wakeup(waitq_t *wq, bool all)
1 jermar 353
{
413 jermar 354
    ipl_t ipl;
1 jermar 355
 
413 jermar 356
    ipl = interrupts_disable();
1 jermar 357
    spinlock_lock(&wq->lock);
358
 
359
    _waitq_wakeup_unsafe(wq, all);
360
 
361
    spinlock_unlock(&wq->lock);
413 jermar 362
    interrupts_restore(ipl);   
1 jermar 363
}
364
 
382 jermar 365
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
366
 *
367
 * This is the internal SMP- and IRQ-unsafe version
368
 * of waitq_wakeup(). It assumes wq->lock is already
369
 * locked and interrupts are already disabled.
370
 *
371
 * @param wq Pointer to wait queue.
372
 * @param all If this is non-zero, all sleeping threads
373
 *        will be woken up and missed count will be zeroed.
1 jermar 374
 */
557 jermar 375
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
1 jermar 376
{
377
    thread_t *t;
378
 
379
loop:  
380
    if (list_empty(&wq->head)) {
381
        wq->missed_wakeups++;
557 jermar 382
        if (all)
383
            wq->missed_wakeups = 0;
1 jermar 384
        return;
385
    }
386
 
387
    t = list_get_instance(wq->head.next, thread_t, wq_link);
388
 
389
    list_remove(&t->wq_link);
390
    spinlock_lock(&t->lock);
391
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
557 jermar 392
        t->timeout_pending = false;
1 jermar 393
    t->sleep_queue = NULL;
394
    spinlock_unlock(&t->lock);
395
 
396
    thread_ready(t);
397
 
557 jermar 398
    if (all)
399
        goto loop;
1 jermar 400
}