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1 jermar 1
/*
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 * Copyright (C) 2001-2004 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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382 jermar 29
#include <synch/waitq.h>
1 jermar 30
#include <synch/synch.h>
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#include <synch/spinlock.h>
382 jermar 32
#include <proc/thread.h>
1 jermar 33
#include <arch/asm.h>
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#include <arch/types.h>
382 jermar 35
#include <time/timeout.h>
1 jermar 36
#include <arch.h>
382 jermar 37
#include <context.h>
1 jermar 38
#include <list.h>
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382 jermar 40
/** Initialize wait queue
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 *
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 * Initialize wait queue.
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 *
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 * @param wq Pointer to wait queue to be initialized.
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 */
1 jermar 46
void waitq_initialize(waitq_t *wq)
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{
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    spinlock_initialize(&wq->lock);
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    list_initialize(&wq->head);
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    wq->missed_wakeups = 0;
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}
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382 jermar 53
/** Handle timeout during waitq_sleep_timeout() call
1 jermar 54
 *
382 jermar 55
 * This routine is called when waitq_sleep_timeout() timeouts.
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 * Interrupts are disabled.
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 *
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 * It is supposed to try to remove 'its' thread from the wait queue;
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 * it can eventually fail to achieve this goal when these two events
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 * overlap. In that case it behaves just as though there was no
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 * timeout at all.
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 *
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 * @param data Pointer to the thread that called waitq_sleep_timeout().
1 jermar 64
 */
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void waitq_interrupted_sleep(void *data)
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{
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    thread_t *t = (thread_t *) data;
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    waitq_t *wq;
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    int do_wakeup = 0;
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    spinlock_lock(&threads_lock);
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    if (!list_member(&t->threads_link, &threads_head))
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        goto out;
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grab_locks:
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    spinlock_lock(&t->lock);
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    if (wq = t->sleep_queue) {
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        if (!spinlock_trylock(&wq->lock)) {
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            spinlock_unlock(&t->lock);
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            goto grab_locks; /* avoid deadlock */
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        }
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        list_remove(&t->wq_link);
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        t->saved_context = t->sleep_timeout_context;
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        do_wakeup = 1;
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        spinlock_unlock(&wq->lock);
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        t->sleep_queue = NULL;
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    }
90
 
91
    t->timeout_pending = 0;
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    spinlock_unlock(&t->lock);
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94
    if (do_wakeup) thread_ready(t);
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out:
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    spinlock_unlock(&threads_lock);
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}
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382 jermar 100
/** Sleep until either wakeup or timeout occurs
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 *
1 jermar 102
 * This is a sleep implementation which allows itself to be
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 * interrupted from the sleep, restoring a failover context.
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 *
382 jermar 105
 * Sleepers are organised in FIFO fashion in a structure called wait queue.
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 *
1 jermar 107
 * This function is really basic in that other functions as waitq_sleep()
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 * and all the *_timeout() functions use it.
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 *
382 jermar 110
 * @param wq Pointer to wait queue.
404 jermar 111
 * @param usec Timeout in microseconds.
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 * @param nonblocking Blocking vs. non-blocking operation mode switch.
1 jermar 113
 *
404 jermar 114
 * If usec is greater than zero, regardless of the value of @nonblocking,
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 * the call will not return until either timeout or wakeup comes.
382 jermar 116
 *
404 jermar 117
 * If usec is zero and nonblocking is zero (false), the call
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 * will not return until wakeup comes.
1 jermar 119
 *
404 jermar 120
 * If usec is zero and nonblocking is non-zero (true), the call will
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 * immediately return, reporting either success or failure.
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 *
382 jermar 123
 * @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
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 *         ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
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 *
404 jermar 126
 * ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
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 * of the call there was no pending wakeup.
382 jermar 128
 *
404 jermar 129
 * ESYNCH_TIMEOUT means that the sleep timed out.
130
 *
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 * ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
132
 * a pending wakeup at the time of the call. The caller was not put
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 * asleep at all.
134
 *
135
 * ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
136
 * attempted.
1 jermar 137
 */
138
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
139
{
140
    volatile pri_t pri; /* must be live after context_restore() */
141
 
142
 
143
restart:
144
    pri = cpu_priority_high();
145
 
146
    /*
147
     * Busy waiting for a delayed timeout.
148
     * This is an important fix for the race condition between
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     * a delayed timeout and a next call to waitq_sleep_timeout().
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     * Simply, the thread is not allowed to go to sleep if
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     * there are timeouts in progress.
152
     */
15 jermar 153
    spinlock_lock(&THREAD->lock);
154
    if (THREAD->timeout_pending) {
155
        spinlock_unlock(&THREAD->lock);
1 jermar 156
        cpu_priority_restore(pri);     
157
        goto restart;
158
    }
15 jermar 159
    spinlock_unlock(&THREAD->lock);
1 jermar 160
 
161
    spinlock_lock(&wq->lock);
162
 
163
    /* checks whether to go to sleep at all */
164
    if (wq->missed_wakeups) {
165
        wq->missed_wakeups--;
166
        spinlock_unlock(&wq->lock);
167
        cpu_priority_restore(pri);
168
        return ESYNCH_OK_ATOMIC;
169
    }
170
    else {
171
        if (nonblocking && (usec == 0)) {
172
            /* return immediatelly instead of going to sleep */
173
            spinlock_unlock(&wq->lock);
174
            cpu_priority_restore(pri);
175
            return ESYNCH_WOULD_BLOCK;
176
        }
177
    }
178
 
179
 
180
    /*
181
     * Now we are firmly decided to go to sleep.
182
     */
15 jermar 183
    spinlock_lock(&THREAD->lock);
1 jermar 184
    if (usec) {
185
        /* We use the timeout variant. */
15 jermar 186
        if (!context_save(&THREAD->sleep_timeout_context)) {
1 jermar 187
            /*
188
             * Short emulation of scheduler() return code.
189
             */
25 jermar 190
            before_thread_runs();
15 jermar 191
            spinlock_unlock(&THREAD->lock);
1 jermar 192
            cpu_priority_restore(pri);
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            return ESYNCH_TIMEOUT;
194
        }
15 jermar 195
        THREAD->timeout_pending = 1;
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        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_interrupted_sleep, THREAD);
1 jermar 197
    }
198
 
15 jermar 199
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 200
 
201
    /*
202
     * Suspend execution.
203
     */
15 jermar 204
    THREAD->state = Sleeping;
205
    THREAD->sleep_queue = wq;
1 jermar 206
 
15 jermar 207
    spinlock_unlock(&THREAD->lock);
1 jermar 208
 
209
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
210
    cpu_priority_restore(pri);
211
 
212
    return ESYNCH_OK_BLOCKED;
213
}
214
 
215
 
382 jermar 216
/** Wake up first thread sleeping in a wait queue
217
 *
218
 * Wake up first thread sleeping in a wait queue.
219
 * This is the SMP- and IRQ-safe wrapper meant for
220
 * general use.
221
 *
222
 * Besides its 'normal' wakeup operation, it attempts
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 * to unregister possible timeout.
224
 *
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 * @param wq Pointer to wait queue.
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 * @param all If this is non-zero, all sleeping threads
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 *        will be woken up and missed count will be zeroed.
1 jermar 228
 */
229
void waitq_wakeup(waitq_t *wq, int all)
230
{
231
    pri_t pri;
232
 
233
    pri = cpu_priority_high();
234
    spinlock_lock(&wq->lock);
235
 
236
    _waitq_wakeup_unsafe(wq, all);
237
 
238
    spinlock_unlock(&wq->lock);
239
    cpu_priority_restore(pri); 
240
}
241
 
382 jermar 242
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
243
 *
244
 * This is the internal SMP- and IRQ-unsafe version
245
 * of waitq_wakeup(). It assumes wq->lock is already
246
 * locked and interrupts are already disabled.
247
 *
248
 * @param wq Pointer to wait queue.
249
 * @param all If this is non-zero, all sleeping threads
250
 *        will be woken up and missed count will be zeroed.
1 jermar 251
 */
252
void _waitq_wakeup_unsafe(waitq_t *wq, int all)
253
{
254
    thread_t *t;
255
 
256
loop:  
257
    if (list_empty(&wq->head)) {
258
        wq->missed_wakeups++;
259
        if (all) wq->missed_wakeups = 0;
260
        return;
261
    }
262
 
263
    t = list_get_instance(wq->head.next, thread_t, wq_link);
264
 
265
    list_remove(&t->wq_link);
266
    spinlock_lock(&t->lock);
267
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
268
        t->timeout_pending = 0;
269
    t->sleep_queue = NULL;
270
    spinlock_unlock(&t->lock);
271
 
272
    thread_ready(t);
273
 
274
    if (all) goto loop;
275
}