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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
18
 * 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>
414 jermar 33
#include <proc/scheduler.h>
1 jermar 34
#include <arch/asm.h>
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#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
 
382 jermar 42
/** 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 48
void waitq_initialize(waitq_t *wq)
49
{
552 palkovsky 50
    spinlock_initialize(&wq->lock, "waitq_lock");
1 jermar 51
    list_initialize(&wq->head);
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    wq->missed_wakeups = 0;
53
}
54
 
382 jermar 55
/** Handle timeout during waitq_sleep_timeout() call
1 jermar 56
 *
382 jermar 57
 * This routine is called when waitq_sleep_timeout() timeouts.
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 * Interrupts are disabled.
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 *
60
 * 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 66
 */
67
void waitq_interrupted_sleep(void *data)
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{
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    thread_t *t = (thread_t *) data;
70
    waitq_t *wq;
557 jermar 71
    bool do_wakeup = false;
1 jermar 72
 
73
    spinlock_lock(&threads_lock);
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    if (!list_member(&t->threads_link, &threads_head))
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        goto out;
76
 
77
grab_locks:
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    spinlock_lock(&t->lock);
615 palkovsky 79
    if ((wq = t->sleep_queue)) {        /* assignment */
1 jermar 80
        if (!spinlock_trylock(&wq->lock)) {
81
            spinlock_unlock(&t->lock);
557 jermar 82
            goto grab_locks;    /* avoid deadlock */
1 jermar 83
        }
84
 
85
        list_remove(&t->wq_link);
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        t->saved_context = t->sleep_timeout_context;
557 jermar 87
        do_wakeup = true;
1 jermar 88
 
89
        spinlock_unlock(&wq->lock);
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        t->sleep_queue = NULL;
91
    }
92
 
557 jermar 93
    t->timeout_pending = false;
1 jermar 94
    spinlock_unlock(&t->lock);
95
 
557 jermar 96
    if (do_wakeup)
97
        thread_ready(t);
1 jermar 98
 
99
out:
100
    spinlock_unlock(&threads_lock);
101
}
102
 
382 jermar 103
/** Sleep until either wakeup or timeout occurs
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 *
1 jermar 105
 * This is a sleep implementation which allows itself to be
106
 * interrupted from the sleep, restoring a failover context.
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 *
382 jermar 108
 * Sleepers are organised in FIFO fashion in a structure called wait queue.
109
 *
1 jermar 110
 * 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 113
 * @param wq Pointer to wait queue.
404 jermar 114
 * @param usec Timeout in microseconds.
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 * @param nonblocking Blocking vs. non-blocking operation mode switch.
1 jermar 116
 *
405 jermar 117
 * If usec is greater than zero, regardless of the value of nonblocking,
404 jermar 118
 * the call will not return until either timeout or wakeup comes.
382 jermar 119
 *
404 jermar 120
 * If usec is zero and nonblocking is zero (false), the call
121
 * will not return until wakeup comes.
1 jermar 122
 *
404 jermar 123
 * If usec is zero and nonblocking is non-zero (true), the call will
124
 * immediately return, reporting either success or failure.
125
 *
382 jermar 126
 * @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
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 *         ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
128
 *
404 jermar 129
 * ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
130
 * of the call there was no pending wakeup.
382 jermar 131
 *
404 jermar 132
 * ESYNCH_TIMEOUT means that the sleep timed out.
133
 *
134
 * ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
135
 * a pending wakeup at the time of the call. The caller was not put
136
 * asleep at all.
137
 *
138
 * ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
139
 * attempted.
1 jermar 140
 */
141
int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
142
{
413 jermar 143
    volatile ipl_t ipl; /* must be live after context_restore() */
1 jermar 144
 
145
 
146
restart:
413 jermar 147
    ipl = interrupts_disable();
1 jermar 148
 
149
    /*
150
     * Busy waiting for a delayed timeout.
151
     * This is an important fix for the race condition between
152
     * a delayed timeout and a next call to waitq_sleep_timeout().
153
     * Simply, the thread is not allowed to go to sleep if
154
     * there are timeouts in progress.
155
     */
15 jermar 156
    spinlock_lock(&THREAD->lock);
157
    if (THREAD->timeout_pending) {
158
        spinlock_unlock(&THREAD->lock);
413 jermar 159
        interrupts_restore(ipl);       
1 jermar 160
        goto restart;
161
    }
15 jermar 162
    spinlock_unlock(&THREAD->lock);
1 jermar 163
 
164
    spinlock_lock(&wq->lock);
165
 
166
    /* checks whether to go to sleep at all */
167
    if (wq->missed_wakeups) {
168
        wq->missed_wakeups--;
169
        spinlock_unlock(&wq->lock);
413 jermar 170
        interrupts_restore(ipl);
1 jermar 171
        return ESYNCH_OK_ATOMIC;
172
    }
173
    else {
174
        if (nonblocking && (usec == 0)) {
175
            /* return immediatelly instead of going to sleep */
176
            spinlock_unlock(&wq->lock);
413 jermar 177
            interrupts_restore(ipl);
1 jermar 178
            return ESYNCH_WOULD_BLOCK;
179
        }
180
    }
181
 
182
 
183
    /*
184
     * Now we are firmly decided to go to sleep.
185
     */
15 jermar 186
    spinlock_lock(&THREAD->lock);
1 jermar 187
    if (usec) {
188
        /* We use the timeout variant. */
15 jermar 189
        if (!context_save(&THREAD->sleep_timeout_context)) {
1 jermar 190
            /*
191
             * Short emulation of scheduler() return code.
192
             */
25 jermar 193
            before_thread_runs();
15 jermar 194
            spinlock_unlock(&THREAD->lock);
413 jermar 195
            interrupts_restore(ipl);
1 jermar 196
            return ESYNCH_TIMEOUT;
197
        }
557 jermar 198
        THREAD->timeout_pending = true;
15 jermar 199
        timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_interrupted_sleep, THREAD);
1 jermar 200
    }
201
 
15 jermar 202
    list_append(&THREAD->wq_link, &wq->head);
1 jermar 203
 
204
    /*
205
     * Suspend execution.
206
     */
15 jermar 207
    THREAD->state = Sleeping;
208
    THREAD->sleep_queue = wq;
1 jermar 209
 
15 jermar 210
    spinlock_unlock(&THREAD->lock);
1 jermar 211
 
212
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
413 jermar 213
    interrupts_restore(ipl);
1 jermar 214
 
215
    return ESYNCH_OK_BLOCKED;
216
}
217
 
218
 
382 jermar 219
/** Wake up first thread sleeping in a wait queue
220
 *
221
 * Wake up first thread sleeping in a wait queue.
222
 * This is the SMP- and IRQ-safe wrapper meant for
223
 * general use.
224
 *
225
 * Besides its 'normal' wakeup operation, it attempts
226
 * to unregister possible timeout.
227
 *
228
 * @param wq Pointer to wait queue.
229
 * @param all If this is non-zero, all sleeping threads
230
 *        will be woken up and missed count will be zeroed.
1 jermar 231
 */
557 jermar 232
void waitq_wakeup(waitq_t *wq, bool all)
1 jermar 233
{
413 jermar 234
    ipl_t ipl;
1 jermar 235
 
413 jermar 236
    ipl = interrupts_disable();
1 jermar 237
    spinlock_lock(&wq->lock);
238
 
239
    _waitq_wakeup_unsafe(wq, all);
240
 
241
    spinlock_unlock(&wq->lock);
413 jermar 242
    interrupts_restore(ipl);   
1 jermar 243
}
244
 
382 jermar 245
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
246
 *
247
 * This is the internal SMP- and IRQ-unsafe version
248
 * of waitq_wakeup(). It assumes wq->lock is already
249
 * locked and interrupts are already disabled.
250
 *
251
 * @param wq Pointer to wait queue.
252
 * @param all If this is non-zero, all sleeping threads
253
 *        will be woken up and missed count will be zeroed.
1 jermar 254
 */
557 jermar 255
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
1 jermar 256
{
257
    thread_t *t;
258
 
259
loop:  
260
    if (list_empty(&wq->head)) {
261
        wq->missed_wakeups++;
557 jermar 262
        if (all)
263
            wq->missed_wakeups = 0;
1 jermar 264
        return;
265
    }
266
 
267
    t = list_get_instance(wq->head.next, thread_t, wq_link);
268
 
269
    list_remove(&t->wq_link);
270
    spinlock_lock(&t->lock);
271
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
557 jermar 272
        t->timeout_pending = false;
1 jermar 273
    t->sleep_queue = NULL;
274
    spinlock_unlock(&t->lock);
275
 
276
    thread_ready(t);
277
 
557 jermar 278
    if (all)
279
        goto loop;
1 jermar 280
}