Subversion Repositories HelenOS

Rev

Rev 1229 | Rev 1288 | Go to most recent revision | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
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
 *
33
 * Wait queue is the basic synchronization primitive upon all
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
 
161
/** Sleep until either wakeup, timeout or interruption occurs
162
 *
1 jermar 163
 * This is a sleep implementation which allows itself to be
164
 * interrupted from the sleep, restoring a failover context.
165
 *
382 jermar 166
 * Sleepers are organised in FIFO fashion in a structure called wait queue.
167
 *
1 jermar 168
 * This function is really basic in that other functions as waitq_sleep()
169
 * and all the *_timeout() functions use it.
170
 *
382 jermar 171
 * @param wq Pointer to wait queue.
404 jermar 172
 * @param usec Timeout in microseconds.
173
 * @param nonblocking Blocking vs. non-blocking operation mode switch.
1 jermar 174
 *
1248 jermar 175
 * If usec is greater than zero, regardless of the value of nonblocking,
404 jermar 176
 * the call will not return until either timeout or wakeup comes.
382 jermar 177
 *
1248 jermar 178
 * If usec is zero and @nonblocking is zero (false), the call
404 jermar 179
 * will not return until wakeup comes.
1 jermar 180
 *
1248 jermar 181
 * If usec is zero and nonblocking is non-zero (true), the call will
404 jermar 182
 * immediately return, reporting either success or failure.
183
 *
1248 jermar 184
 * @return  Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
185
 *          ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
382 jermar 186
 *
1248 jermar 187
 * @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
404 jermar 188
 * of the call there was no pending wakeup.
382 jermar 189
 *
1248 jermar 190
 * @li ESYNCH_TIMEOUT means that the sleep timed out.
404 jermar 191
 *
1248 jermar 192
 * @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
1156 jermar 193
 *
1248 jermar 194
 * @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
404 jermar 195
 * a pending wakeup at the time of the call. The caller was not put
196
 * asleep at all.
197
 *
1248 jermar 198
 * @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
404 jermar 199
 * attempted.
1 jermar 200
 */
201
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
202
{
413 jermar 203
    volatile ipl_t ipl; /* must be live after context_restore() */
1 jermar 204
 
205
 
206
restart:
413 jermar 207
    ipl = interrupts_disable();
1 jermar 208
 
209
    /*
210
     * Busy waiting for a delayed timeout.
211
     * This is an important fix for the race condition between
212
     * a delayed timeout and a next call to waitq_sleep_timeout().
213
     * Simply, the thread is not allowed to go to sleep if
214
     * there are timeouts in progress.
215
     */
15 jermar 216
    spinlock_lock(&THREAD->lock);
217
    if (THREAD->timeout_pending) {
218
        spinlock_unlock(&THREAD->lock);
413 jermar 219
        interrupts_restore(ipl);       
1 jermar 220
        goto restart;
221
    }
15 jermar 222
    spinlock_unlock(&THREAD->lock);
1 jermar 223
 
224
    spinlock_lock(&wq->lock);
225
 
226
    /* checks whether to go to sleep at all */
227
    if (wq->missed_wakeups) {
228
        wq->missed_wakeups--;
229
        spinlock_unlock(&wq->lock);
413 jermar 230
        interrupts_restore(ipl);
1 jermar 231
        return ESYNCH_OK_ATOMIC;
232
    }
233
    else {
234
        if (nonblocking && (usec == 0)) {
235
            /* return immediatelly instead of going to sleep */
236
            spinlock_unlock(&wq->lock);
413 jermar 237
            interrupts_restore(ipl);
1 jermar 238
            return ESYNCH_WOULD_BLOCK;
239
        }
240
    }
241
 
242
    /*
243
     * Now we are firmly decided to go to sleep.
244
     */
15 jermar 245
    spinlock_lock(&THREAD->lock);
1156 jermar 246
 
247
    /*
248
     * Set context that will be restored if the sleep
249
     * of this thread is ever interrupted.
250
     */
251
    if (!context_save(&THREAD->sleep_interruption_context)) {
252
        /* Short emulation of scheduler() return code. */
253
        spinlock_unlock(&THREAD->lock);
254
        interrupts_restore(ipl);
255
        return ESYNCH_INTERRUPTED;
256
    }
257
 
1 jermar 258
    if (usec) {
259
        /* We use the timeout variant. */
15 jermar 260
        if (!context_save(&THREAD->sleep_timeout_context)) {
1156 jermar 261
            /* Short emulation of scheduler() return code. */
15 jermar 262
            spinlock_unlock(&THREAD->lock);
413 jermar 263
            interrupts_restore(ipl);
1 jermar 264
            return ESYNCH_TIMEOUT;
265
        }
557 jermar 266
        THREAD->timeout_pending = true;
1156 jermar 267
        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
1 jermar 268
    }
269
 
15 jermar 270
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 271
 
272
    /*
273
     * Suspend execution.
274
     */
15 jermar 275
    THREAD->state = Sleeping;
276
    THREAD->sleep_queue = wq;
1 jermar 277
 
15 jermar 278
    spinlock_unlock(&THREAD->lock);
1 jermar 279
 
280
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
413 jermar 281
    interrupts_restore(ipl);
1 jermar 282
 
283
    return ESYNCH_OK_BLOCKED;
284
}
285
 
286
 
382 jermar 287
/** Wake up first thread sleeping in a wait queue
288
 *
289
 * Wake up first thread sleeping in a wait queue.
290
 * This is the SMP- and IRQ-safe wrapper meant for
291
 * general use.
292
 *
293
 * Besides its 'normal' wakeup operation, it attempts
294
 * to unregister possible timeout.
295
 *
296
 * @param wq Pointer to wait queue.
297
 * @param all If this is non-zero, all sleeping threads
298
 *        will be woken up and missed count will be zeroed.
1 jermar 299
 */
557 jermar 300
void waitq_wakeup(waitq_t *wq, bool all)
1 jermar 301
{
413 jermar 302
    ipl_t ipl;
1 jermar 303
 
413 jermar 304
    ipl = interrupts_disable();
1 jermar 305
    spinlock_lock(&wq->lock);
306
 
307
    _waitq_wakeup_unsafe(wq, all);
308
 
309
    spinlock_unlock(&wq->lock);
413 jermar 310
    interrupts_restore(ipl);   
1 jermar 311
}
312
 
382 jermar 313
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
314
 *
315
 * This is the internal SMP- and IRQ-unsafe version
316
 * of waitq_wakeup(). It assumes wq->lock is already
317
 * locked and interrupts are already disabled.
318
 *
319
 * @param wq Pointer to wait queue.
320
 * @param all If this is non-zero, all sleeping threads
321
 *        will be woken up and missed count will be zeroed.
1 jermar 322
 */
557 jermar 323
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
1 jermar 324
{
325
    thread_t *t;
326
 
327
loop:  
328
    if (list_empty(&wq->head)) {
329
        wq->missed_wakeups++;
557 jermar 330
        if (all)
331
            wq->missed_wakeups = 0;
1 jermar 332
        return;
333
    }
334
 
335
    t = list_get_instance(wq->head.next, thread_t, wq_link);
336
 
337
    list_remove(&t->wq_link);
338
    spinlock_lock(&t->lock);
339
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
557 jermar 340
        t->timeout_pending = false;
1 jermar 341
    t->sleep_queue = NULL;
342
    spinlock_unlock(&t->lock);
343
 
344
    thread_ready(t);
345
 
557 jermar 346
    if (all)
347
        goto loop;
1 jermar 348
}