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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;
/*
* !!!
* This function MUST handle a NULL session handle.
*/
WT_RET(__wt_calloc_one(session, &cond));
InitializeCriticalSection(&cond->mtx);
/* Initialize the condition variable to permit self-blocking. */
InitializeConditionVariable(&cond->cond);
cond->name = name;
cond->waiters = is_signalled ? -1 : 0;
*condp = cond;
return (0);
}
/*
* __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.
*/
int
__wt_cond_wait_signal(
WT_SESSION_IMPL *session, WT_CONDVAR *cond, uint64_t usecs, bool *signalled)
{
BOOL sleepret;
DWORD milliseconds, windows_error;
bool locked;
uint64_t milliseconds64;
locked = false;
/* Fast path if already signalled. */
*signalled = true;
if (__wt_atomic_addi32(&cond->waiters, 1) == 0)
return (0);
/*
* !!!
* This function MUST handle a NULL session handle.
*/
if (session != NULL) {
WT_RET(__wt_verbose(session, WT_VERB_MUTEX,
"wait %s cond (%p)", cond->name, cond));
WT_STAT_FAST_CONN_INCR(session, cond_wait);
}
EnterCriticalSection(&cond->mtx);
locked = true;
if (usecs > 0) {
milliseconds64 = usecs / 1000;
/*
* Check for 32-bit unsigned integer overflow
* INFINITE is max unsigned int on Windows
*/
if (milliseconds64 >= INFINITE)
milliseconds64 = INFINITE - 1;
milliseconds = (DWORD)milliseconds64;
/*
* 0 would mean the CV sleep becomes a TryCV which we do not
* want
*/
if (milliseconds == 0)
milliseconds = 1;
sleepret = SleepConditionVariableCS(
&cond->cond, &cond->mtx, milliseconds);
} else
sleepret = SleepConditionVariableCS(
&cond->cond, &cond->mtx, INFINITE);
/*
* SleepConditionVariableCS returns non-zero on success, 0 on timeout
* or failure.
*/
if (sleepret == 0) {
windows_error = __wt_getlasterror();
if (windows_error == ERROR_TIMEOUT) {
*signalled = false;
sleepret = 1;
}
}
(void)__wt_atomic_subi32(&cond->waiters, 1);
if (locked)
LeaveCriticalSection(&cond->mtx);
if (sleepret != 0)
return (0);
__wt_errx(session, "SleepConditionVariableCS: %s",
__wt_formatmessage(session, windows_error));
return (__wt_map_windows_error(windows_error));
}
/*
* __wt_cond_signal --
* Signal a waiting thread.
*/
int
__wt_cond_signal(WT_SESSION_IMPL *session, WT_CONDVAR *cond)
{
WT_DECL_RET;
bool locked;
locked = false;
/*
* !!!
* This function MUST handle a NULL session handle.
*/
if (session != NULL)
WT_RET(__wt_verbose(session, WT_VERB_MUTEX,
"signal %s cond (%p)", cond->name, cond));
/* Fast path if already signalled. */
if (cond->waiters == -1)
return (0);
if (cond->waiters > 0 || !__wt_atomic_casi32(&cond->waiters, 0, -1)) {
EnterCriticalSection(&cond->mtx);
locked = true;
WakeAllConditionVariable(&cond->cond);
}
if (locked)
LeaveCriticalSection(&cond->mtx);
if (ret == 0)
return (0);
WT_RET_MSG(session, ret, "WakeAllConditionVariable");
}
/*
* __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);
/* Do nothing to delete Condition Variable */
DeleteCriticalSection(&cond->mtx);
__wt_free(session, *condp);
return (ret);
}
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