Source code
Revision control
Copy as Markdown
Other Tools
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "primpl.h"
/************************************************************************/
/*
* Notifies just get posted to the monitor. The actual notification is done
* when the monitor is fully exited so that MP systems don't contend for a
* monitor that they can't enter.
*/
static void _PR_PostNotifyToMonitor(PRMonitor* mon, PRBool broadcast) {
PR_ASSERT(mon != NULL);
PR_ASSERT_CURRENT_THREAD_IN_MONITOR(mon);
/* mon->notifyTimes is protected by the monitor, so we don't need to
* acquire mon->lock.
*/
if (broadcast) {
mon->notifyTimes = -1;
} else if (mon->notifyTimes != -1) {
mon->notifyTimes += 1;
}
}
static void _PR_PostNotifiesFromMonitor(PRCondVar* cv, PRIntn times) {
PRStatus rv;
/*
* Time to actually notify any waits that were affected while the monitor
* was entered.
*/
PR_ASSERT(cv != NULL);
PR_ASSERT(times != 0);
if (times == -1) {
rv = PR_NotifyAllCondVar(cv);
PR_ASSERT(rv == PR_SUCCESS);
} else {
while (times-- > 0) {
rv = PR_NotifyCondVar(cv);
PR_ASSERT(rv == PR_SUCCESS);
}
}
}
/*
** Create a new monitor.
*/
PR_IMPLEMENT(PRMonitor*) PR_NewMonitor() {
PRMonitor* mon;
PRStatus rv;
if (!_pr_initialized) {
_PR_ImplicitInitialization();
}
mon = PR_NEWZAP(PRMonitor);
if (mon == NULL) {
PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
return NULL;
}
rv = _PR_InitLock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
if (rv != PR_SUCCESS) {
goto error1;
}
mon->owner = NULL;
rv = _PR_InitCondVar(&mon->entryCV, &mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
if (rv != PR_SUCCESS) {
goto error2;
}
rv = _PR_InitCondVar(&mon->waitCV, &mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
if (rv != PR_SUCCESS) {
goto error3;
}
mon->notifyTimes = 0;
mon->entryCount = 0;
mon->name = NULL;
return mon;
error3:
_PR_FreeCondVar(&mon->entryCV);
error2:
_PR_FreeLock(&mon->lock);
error1:
PR_Free(mon);
return NULL;
}
PR_IMPLEMENT(PRMonitor*) PR_NewNamedMonitor(const char* name) {
PRMonitor* mon = PR_NewMonitor();
if (mon) {
mon->name = name;
}
return mon;
}
/*
** Destroy a monitor. There must be no thread waiting on the monitor's
** condition variable. The caller is responsible for guaranteeing that the
** monitor is no longer in use.
*/
PR_IMPLEMENT(void) PR_DestroyMonitor(PRMonitor* mon) {
PR_ASSERT(mon != NULL);
_PR_FreeCondVar(&mon->waitCV);
_PR_FreeCondVar(&mon->entryCV);
_PR_FreeLock(&mon->lock);
#if defined(DEBUG)
memset(mon, 0xaf, sizeof(PRMonitor));
#endif
PR_Free(mon);
}
/*
** Enter the lock associated with the monitor.
*/
PR_IMPLEMENT(void) PR_EnterMonitor(PRMonitor* mon) {
PRThread* me = _PR_MD_CURRENT_THREAD();
PRStatus rv;
PR_ASSERT(mon != NULL);
PR_Lock(&mon->lock);
if (mon->entryCount != 0) {
if (mon->owner == me) {
goto done;
}
while (mon->entryCount != 0) {
rv = PR_WaitCondVar(&mon->entryCV, PR_INTERVAL_NO_TIMEOUT);
PR_ASSERT(rv == PR_SUCCESS);
}
}
/* and now I have the monitor */
PR_ASSERT(mon->notifyTimes == 0);
PR_ASSERT(mon->owner == NULL);
mon->owner = me;
done:
mon->entryCount += 1;
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
}
/*
** Test and then enter the lock associated with the monitor if it's not
** already entered by some other thread. Return PR_FALSE if some other
** thread owned the lock at the time of the call.
*/
PR_IMPLEMENT(PRBool) PR_TestAndEnterMonitor(PRMonitor* mon) {
PRThread* me = _PR_MD_CURRENT_THREAD();
PRStatus rv;
PR_ASSERT(mon != NULL);
PR_Lock(&mon->lock);
if (mon->entryCount != 0) {
if (mon->owner == me) {
goto done;
}
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
return PR_FALSE;
}
/* and now I have the monitor */
PR_ASSERT(mon->notifyTimes == 0);
PR_ASSERT(mon->owner == NULL);
mon->owner = me;
done:
mon->entryCount += 1;
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
return PR_TRUE;
}
/*
** Exit the lock associated with the monitor once.
*/
PR_IMPLEMENT(PRStatus) PR_ExitMonitor(PRMonitor* mon) {
PRThread* me = _PR_MD_CURRENT_THREAD();
PRStatus rv;
PR_ASSERT(mon != NULL);
PR_Lock(&mon->lock);
/* the entries should be > 0 and we'd better be the owner */
PR_ASSERT(mon->entryCount > 0);
PR_ASSERT(mon->owner == me);
if (mon->entryCount == 0 || mon->owner != me) {
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
return PR_FAILURE;
}
mon->entryCount -= 1; /* reduce by one */
if (mon->entryCount == 0) {
/* and if it transitioned to zero - notify an entry waiter */
/* make the owner unknown */
mon->owner = NULL;
if (mon->notifyTimes != 0) {
_PR_PostNotifiesFromMonitor(&mon->waitCV, mon->notifyTimes);
mon->notifyTimes = 0;
}
rv = PR_NotifyCondVar(&mon->entryCV);
PR_ASSERT(rv == PR_SUCCESS);
}
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
return PR_SUCCESS;
}
/*
** Return the number of times that the current thread has entered the
** lock. Returns zero if the current thread has not entered the lock.
*/
PR_IMPLEMENT(PRIntn) PR_GetMonitorEntryCount(PRMonitor* mon) {
PRThread* me = _PR_MD_CURRENT_THREAD();
PRStatus rv;
PRIntn count = 0;
PR_Lock(&mon->lock);
if (mon->owner == me) {
count = mon->entryCount;
}
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
return count;
}
PR_IMPLEMENT(void) PR_AssertCurrentThreadInMonitor(PRMonitor* mon) {
#if defined(DEBUG) || defined(FORCE_PR_ASSERT)
PRStatus rv;
PR_Lock(&mon->lock);
PR_ASSERT(mon->entryCount != 0 && mon->owner == _PR_MD_CURRENT_THREAD());
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
#endif
}
/*
** Wait for a notify on the condition variable. Sleep for "ticks" amount
** of time (if "tick" is 0 then the sleep is indefinite). While
** the thread is waiting it exits the monitors lock (as if it called
** PR_ExitMonitor as many times as it had called PR_EnterMonitor). When
** the wait has finished the thread regains control of the monitors lock
** with the same entry count as before the wait began.
**
** The thread waiting on the monitor will be resumed when the monitor is
** notified (assuming the thread is the next in line to receive the
** notify) or when the "ticks" elapses.
**
** Returns PR_FAILURE if the caller has not locked the lock associated
** with the condition variable.
** This routine can return PR_PENDING_INTERRUPT_ERROR if the waiting thread
** has been interrupted.
*/
PR_IMPLEMENT(PRStatus) PR_Wait(PRMonitor* mon, PRIntervalTime ticks) {
PRStatus rv;
PRUint32 saved_entries;
PRThread* saved_owner;
PR_ASSERT(mon != NULL);
PR_Lock(&mon->lock);
/* the entries better be positive */
PR_ASSERT(mon->entryCount > 0);
/* and it better be owned by us */
PR_ASSERT(mon->owner == _PR_MD_CURRENT_THREAD()); /* XXX return failure */
/* tuck these away 'till later */
saved_entries = mon->entryCount;
mon->entryCount = 0;
saved_owner = mon->owner;
mon->owner = NULL;
/* If we have pending notifies, post them now. */
if (mon->notifyTimes != 0) {
_PR_PostNotifiesFromMonitor(&mon->waitCV, mon->notifyTimes);
mon->notifyTimes = 0;
}
rv = PR_NotifyCondVar(&mon->entryCV);
PR_ASSERT(rv == PR_SUCCESS);
rv = PR_WaitCondVar(&mon->waitCV, ticks);
PR_ASSERT(rv == PR_SUCCESS);
while (mon->entryCount != 0) {
rv = PR_WaitCondVar(&mon->entryCV, PR_INTERVAL_NO_TIMEOUT);
PR_ASSERT(rv == PR_SUCCESS);
}
PR_ASSERT(mon->notifyTimes == 0);
/* reinstate the interesting information */
mon->entryCount = saved_entries;
mon->owner = saved_owner;
rv = PR_Unlock(&mon->lock);
PR_ASSERT(rv == PR_SUCCESS);
return rv;
}
/*
** Notify the highest priority thread waiting on the condition
** variable. If a thread is waiting on the condition variable (using
** PR_Wait) then it is awakened and begins waiting on the monitor's lock.
*/
PR_IMPLEMENT(PRStatus) PR_Notify(PRMonitor* mon) {
_PR_PostNotifyToMonitor(mon, PR_FALSE);
return PR_SUCCESS;
}
/*
** Notify all of the threads waiting on the condition variable. All of
** threads are notified in turn. The highest priority thread will
** probably acquire the monitor first when the monitor is exited.
*/
PR_IMPLEMENT(PRStatus) PR_NotifyAll(PRMonitor* mon) {
_PR_PostNotifyToMonitor(mon, PR_TRUE);
return PR_SUCCESS;
}
/************************************************************************/
PRUint32 _PR_MonitorToString(PRMonitor* mon, char* buf, PRUint32 buflen) {
PRUint32 nb;
if (mon->owner) {
nb = PR_snprintf(buf, buflen, "[%p] owner=%d[%p] count=%ld", mon,
mon->owner->id, mon->owner, mon->entryCount);
} else {
nb = PR_snprintf(buf, buflen, "[%p]", mon);
}
return nb;
}