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/*-
* Copyright (c) 2014-2016 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
/*
* __wt_cond_alloc --
* Allocate and initialize a condition variable.
*/
int
__wt_cond_alloc(WT_SESSION_IMPL *session,
const char *name, bool is_signalled, WT_CONDVAR **condp)
{
WT_CONDVAR *cond;
WT_DECL_RET;
WT_RET(__wt_calloc_one(session, &cond));
WT_ERR(pthread_mutex_init(&cond->mtx, NULL));
/* Initialize the condition variable to permit self-blocking. */
WT_ERR(pthread_cond_init(&cond->cond, NULL));
cond->name = name;
cond->waiters = is_signalled ? -1 : 0;
*condp = cond;
return (0);
err: __wt_free(session, cond);
return (ret);
}
/*
* __wt_cond_wait_signal --
* Wait on a mutex, optionally timing out. If we get it before the time
* out period expires, let the caller know.
*/
void
__wt_cond_wait_signal(
WT_SESSION_IMPL *session, WT_CONDVAR *cond, uint64_t usecs, bool *signalled)
{
struct timespec ts;
WT_DECL_RET;
bool locked;
locked = false;
/* Fast path if already signalled. */
*signalled = true;
if (__wt_atomic_addi32(&cond->waiters, 1) == 0)
return;
__wt_verbose(session, WT_VERB_MUTEX, "wait %s", cond->name);
WT_STAT_CONN_INCR(session, cond_wait);
WT_ERR(pthread_mutex_lock(&cond->mtx));
locked = true;
if (usecs > 0) {
WT_ERR(__wt_epoch(session, &ts));
ts.tv_sec += (time_t)
(((uint64_t)ts.tv_nsec + WT_THOUSAND * usecs) / WT_BILLION);
ts.tv_nsec = (long)
(((uint64_t)ts.tv_nsec + WT_THOUSAND * usecs) % WT_BILLION);
ret = pthread_cond_timedwait(&cond->cond, &cond->mtx, &ts);
} else
ret = pthread_cond_wait(&cond->cond, &cond->mtx);
/*
* Check pthread_cond_wait() return for EINTR, ETIME and
* ETIMEDOUT, some systems return these errors.
*/
if (ret == EINTR ||
#ifdef ETIME
ret == ETIME ||
#endif
ret == ETIMEDOUT) {
*signalled = false;
ret = 0;
}
err: (void)__wt_atomic_subi32(&cond->waiters, 1);
if (locked)
WT_TRET(pthread_mutex_unlock(&cond->mtx));
if (ret == 0)
return;
WT_PANIC_MSG(session, ret, "pthread_cond_wait: %s", cond->name);
}
/*
* __wt_cond_signal --
* Signal a waiting thread.
*/
void
__wt_cond_signal(WT_SESSION_IMPL *session, WT_CONDVAR *cond)
{
WT_DECL_RET;
bool locked;
locked = false;
__wt_verbose(session, WT_VERB_MUTEX, "signal %s", cond->name);
/* Fast path if already signalled. */
if (cond->waiters == -1)
return;
if (cond->waiters > 0 || !__wt_atomic_casi32(&cond->waiters, 0, -1)) {
WT_ERR(pthread_mutex_lock(&cond->mtx));
locked = true;
WT_ERR(pthread_cond_broadcast(&cond->cond));
}
err: if (locked)
WT_TRET(pthread_mutex_unlock(&cond->mtx));
if (ret == 0)
return;
WT_PANIC_MSG(session, ret, "pthread_cond_broadcast: %s", cond->name);
}
/*
* __wt_cond_destroy --
* Destroy a condition variable.
*/
int
__wt_cond_destroy(WT_SESSION_IMPL *session, WT_CONDVAR **condp)
{
WT_CONDVAR *cond;
WT_DECL_RET;
cond = *condp;
if (cond == NULL)
return (0);
ret = pthread_cond_destroy(&cond->cond);
WT_TRET(pthread_mutex_destroy(&cond->mtx));
__wt_free(session, *condp);
return (ret);
}
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