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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
 
382 jermar 29
#include <synch/waitq.h>
1 jermar 30
#include <synch/synch.h>
31
#include <synch/spinlock.h>
382 jermar 32
#include <proc/thread.h>
414 jermar 33
#include <proc/scheduler.h>
1 jermar 34
#include <arch/asm.h>
35
#include <arch/types.h>
557 jermar 36
#include <typedefs.h>
382 jermar 37
#include <time/timeout.h>
1 jermar 38
#include <arch.h>
382 jermar 39
#include <context.h>
788 jermar 40
#include <adt/list.h>
1 jermar 41
 
1156 jermar 42
static void waitq_timeouted_sleep(void *data);
43
 
382 jermar 44
/** Initialize wait queue
45
 *
46
 * Initialize wait queue.
47
 *
48
 * @param wq Pointer to wait queue to be initialized.
49
 */
1 jermar 50
void waitq_initialize(waitq_t *wq)
51
{
552 palkovsky 52
    spinlock_initialize(&wq->lock, "waitq_lock");
1 jermar 53
    list_initialize(&wq->head);
54
    wq->missed_wakeups = 0;
55
}
56
 
382 jermar 57
/** Handle timeout during waitq_sleep_timeout() call
1 jermar 58
 *
382 jermar 59
 * This routine is called when waitq_sleep_timeout() timeouts.
60
 * Interrupts are disabled.
61
 *
62
 * It is supposed to try to remove 'its' thread from the wait queue;
63
 * it can eventually fail to achieve this goal when these two events
64
 * overlap. In that case it behaves just as though there was no
65
 * timeout at all.
66
 *
67
 * @param data Pointer to the thread that called waitq_sleep_timeout().
1 jermar 68
 */
1156 jermar 69
void waitq_timeouted_sleep(void *data)
1 jermar 70
{
71
    thread_t *t = (thread_t *) data;
72
    waitq_t *wq;
557 jermar 73
    bool do_wakeup = false;
1 jermar 74
 
75
    spinlock_lock(&threads_lock);
1158 jermar 76
    if (!thread_exists(t))
1 jermar 77
        goto out;
78
 
79
grab_locks:
80
    spinlock_lock(&t->lock);
615 palkovsky 81
    if ((wq = t->sleep_queue)) {        /* assignment */
1 jermar 82
        if (!spinlock_trylock(&wq->lock)) {
83
            spinlock_unlock(&t->lock);
557 jermar 84
            goto grab_locks;    /* avoid deadlock */
1 jermar 85
        }
86
 
87
        list_remove(&t->wq_link);
88
        t->saved_context = t->sleep_timeout_context;
557 jermar 89
        do_wakeup = true;
1 jermar 90
 
91
        spinlock_unlock(&wq->lock);
92
        t->sleep_queue = NULL;
93
    }
94
 
557 jermar 95
    t->timeout_pending = false;
1 jermar 96
    spinlock_unlock(&t->lock);
97
 
557 jermar 98
    if (do_wakeup)
99
        thread_ready(t);
1 jermar 100
 
101
out:
102
    spinlock_unlock(&threads_lock);
103
}
104
 
1156 jermar 105
/** Interrupt sleeping thread.
382 jermar 106
 *
1156 jermar 107
 * This routine attempts to interrupt a thread from its sleep in a waitqueue.
108
 * If the thread is not found sleeping, no action is taken.
109
 *
110
 * @param t Thread to be interrupted.
111
 */
112
void waitq_interrupt_sleep(thread_t *t)
113
{
114
    waitq_t *wq;
115
    bool do_wakeup = false;
116
    ipl_t ipl;
117
 
118
    ipl = interrupts_disable();
119
    spinlock_lock(&threads_lock);
1158 jermar 120
    if (!thread_exists(t))
1156 jermar 121
        goto out;
122
 
123
grab_locks:
124
    spinlock_lock(&t->lock);
125
    if ((wq = t->sleep_queue)) {        /* assignment */
126
        if (!spinlock_trylock(&wq->lock)) {
127
            spinlock_unlock(&t->lock);
128
            goto grab_locks;    /* avoid deadlock */
129
        }
130
 
131
        list_remove(&t->wq_link);
132
        t->saved_context = t->sleep_interruption_context;
133
        do_wakeup = true;
134
 
135
        spinlock_unlock(&wq->lock);
136
        t->sleep_queue = NULL;
137
    }
138
    spinlock_unlock(&t->lock);
139
 
140
    if (do_wakeup)
141
        thread_ready(t);
142
 
143
out:
144
    spinlock_unlock(&threads_lock);
145
    interrupts_restore(ipl);
146
}
147
 
148
 
149
/** Sleep until either wakeup, timeout or interruption occurs
150
 *
1 jermar 151
 * This is a sleep implementation which allows itself to be
152
 * interrupted from the sleep, restoring a failover context.
153
 *
382 jermar 154
 * Sleepers are organised in FIFO fashion in a structure called wait queue.
155
 *
1 jermar 156
 * This function is really basic in that other functions as waitq_sleep()
157
 * and all the *_timeout() functions use it.
158
 *
382 jermar 159
 * @param wq Pointer to wait queue.
404 jermar 160
 * @param usec Timeout in microseconds.
161
 * @param nonblocking Blocking vs. non-blocking operation mode switch.
1 jermar 162
 *
1229 jermar 163
 * If @usec is greater than zero, regardless of the value of @nonblocking,
404 jermar 164
 * the call will not return until either timeout or wakeup comes.
382 jermar 165
 *
1229 jermar 166
 * If @usec is zero and @nonblocking is zero (false), the call
404 jermar 167
 * will not return until wakeup comes.
1 jermar 168
 *
1229 jermar 169
 * If @usec is zero and @nonblocking is non-zero (true), the call will
404 jermar 170
 * immediately return, reporting either success or failure.
171
 *
382 jermar 172
 * @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
173
 *         ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
174
 *
404 jermar 175
 * ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
176
 * of the call there was no pending wakeup.
382 jermar 177
 *
404 jermar 178
 * ESYNCH_TIMEOUT means that the sleep timed out.
179
 *
1156 jermar 180
 * ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
181
 *
404 jermar 182
 * ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
183
 * a pending wakeup at the time of the call. The caller was not put
184
 * asleep at all.
185
 *
186
 * ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
187
 * attempted.
1 jermar 188
 */
189
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
190
{
413 jermar 191
    volatile ipl_t ipl; /* must be live after context_restore() */
1 jermar 192
 
193
 
194
restart:
413 jermar 195
    ipl = interrupts_disable();
1 jermar 196
 
197
    /*
198
     * Busy waiting for a delayed timeout.
199
     * This is an important fix for the race condition between
200
     * a delayed timeout and a next call to waitq_sleep_timeout().
201
     * Simply, the thread is not allowed to go to sleep if
202
     * there are timeouts in progress.
203
     */
15 jermar 204
    spinlock_lock(&THREAD->lock);
205
    if (THREAD->timeout_pending) {
206
        spinlock_unlock(&THREAD->lock);
413 jermar 207
        interrupts_restore(ipl);       
1 jermar 208
        goto restart;
209
    }
15 jermar 210
    spinlock_unlock(&THREAD->lock);
1 jermar 211
 
212
    spinlock_lock(&wq->lock);
213
 
214
    /* checks whether to go to sleep at all */
215
    if (wq->missed_wakeups) {
216
        wq->missed_wakeups--;
217
        spinlock_unlock(&wq->lock);
413 jermar 218
        interrupts_restore(ipl);
1 jermar 219
        return ESYNCH_OK_ATOMIC;
220
    }
221
    else {
222
        if (nonblocking && (usec == 0)) {
223
            /* return immediatelly instead of going to sleep */
224
            spinlock_unlock(&wq->lock);
413 jermar 225
            interrupts_restore(ipl);
1 jermar 226
            return ESYNCH_WOULD_BLOCK;
227
        }
228
    }
229
 
230
    /*
231
     * Now we are firmly decided to go to sleep.
232
     */
15 jermar 233
    spinlock_lock(&THREAD->lock);
1156 jermar 234
 
235
    /*
236
     * Set context that will be restored if the sleep
237
     * of this thread is ever interrupted.
238
     */
239
    if (!context_save(&THREAD->sleep_interruption_context)) {
240
        /* Short emulation of scheduler() return code. */
241
        spinlock_unlock(&THREAD->lock);
242
        interrupts_restore(ipl);
243
        return ESYNCH_INTERRUPTED;
244
    }
245
 
1 jermar 246
    if (usec) {
247
        /* We use the timeout variant. */
15 jermar 248
        if (!context_save(&THREAD->sleep_timeout_context)) {
1156 jermar 249
            /* Short emulation of scheduler() return code. */
15 jermar 250
            spinlock_unlock(&THREAD->lock);
413 jermar 251
            interrupts_restore(ipl);
1 jermar 252
            return ESYNCH_TIMEOUT;
253
        }
557 jermar 254
        THREAD->timeout_pending = true;
1156 jermar 255
        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
1 jermar 256
    }
257
 
15 jermar 258
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 259
 
260
    /*
261
     * Suspend execution.
262
     */
15 jermar 263
    THREAD->state = Sleeping;
264
    THREAD->sleep_queue = wq;
1 jermar 265
 
15 jermar 266
    spinlock_unlock(&THREAD->lock);
1 jermar 267
 
268
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
413 jermar 269
    interrupts_restore(ipl);
1 jermar 270
 
271
    return ESYNCH_OK_BLOCKED;
272
}
273
 
274
 
382 jermar 275
/** Wake up first thread sleeping in a wait queue
276
 *
277
 * Wake up first thread sleeping in a wait queue.
278
 * This is the SMP- and IRQ-safe wrapper meant for
279
 * general use.
280
 *
281
 * Besides its 'normal' wakeup operation, it attempts
282
 * to unregister possible timeout.
283
 *
284
 * @param wq Pointer to wait queue.
285
 * @param all If this is non-zero, all sleeping threads
286
 *        will be woken up and missed count will be zeroed.
1 jermar 287
 */
557 jermar 288
void waitq_wakeup(waitq_t *wq, bool all)
1 jermar 289
{
413 jermar 290
    ipl_t ipl;
1 jermar 291
 
413 jermar 292
    ipl = interrupts_disable();
1 jermar 293
    spinlock_lock(&wq->lock);
294
 
295
    _waitq_wakeup_unsafe(wq, all);
296
 
297
    spinlock_unlock(&wq->lock);
413 jermar 298
    interrupts_restore(ipl);   
1 jermar 299
}
300
 
382 jermar 301
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
302
 *
303
 * This is the internal SMP- and IRQ-unsafe version
304
 * of waitq_wakeup(). It assumes wq->lock is already
305
 * locked and interrupts are already disabled.
306
 *
307
 * @param wq Pointer to wait queue.
308
 * @param all If this is non-zero, all sleeping threads
309
 *        will be woken up and missed count will be zeroed.
1 jermar 310
 */
557 jermar 311
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
1 jermar 312
{
313
    thread_t *t;
314
 
315
loop:  
316
    if (list_empty(&wq->head)) {
317
        wq->missed_wakeups++;
557 jermar 318
        if (all)
319
            wq->missed_wakeups = 0;
1 jermar 320
        return;
321
    }
322
 
323
    t = list_get_instance(wq->head.next, thread_t, wq_link);
324
 
325
    list_remove(&t->wq_link);
326
    spinlock_lock(&t->lock);
327
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
557 jermar 328
        t->timeout_pending = false;
1 jermar 329
    t->sleep_queue = NULL;
330
    spinlock_unlock(&t->lock);
331
 
332
    thread_ready(t);
333
 
557 jermar 334
    if (all)
335
        goto loop;
1 jermar 336
}