diff options
Diffstat (limited to 'nsprpub/pr/src/threads/prmon.c')
| -rw-r--r-- | nsprpub/pr/src/threads/prmon.c | 357 |
1 files changed, 357 insertions, 0 deletions
diff --git a/nsprpub/pr/src/threads/prmon.c b/nsprpub/pr/src/threads/prmon.c new file mode 100644 index 0000000000..b7c526eea7 --- /dev/null +++ b/nsprpub/pr/src/threads/prmon.c @@ -0,0 +1,357 @@ +/* -*- 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 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#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; +} |