diff options
Diffstat (limited to 'nsprpub/pr/src/md/os2/os2cv.c')
| -rw-r--r-- | nsprpub/pr/src/md/os2/os2cv.c | 330 |
1 files changed, 330 insertions, 0 deletions
diff --git a/nsprpub/pr/src/md/os2/os2cv.c b/nsprpub/pr/src/md/os2/os2cv.c new file mode 100644 index 000000000..2c424c50b --- /dev/null +++ b/nsprpub/pr/src/md/os2/os2cv.c @@ -0,0 +1,330 @@ +/* -*- 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/. */ + +/* + * os2cv.c -- OS/2 Machine-Dependent Code for Condition Variables + * + * We implement our own condition variable wait queue. Each thread + * has a semaphore object (thread->md.blocked_sema) to block on while + * waiting on a condition variable. + * + * We use a deferred condition notify algorithm. When PR_NotifyCondVar + * or PR_NotifyAllCondVar is called, the condition notifies are simply + * recorded in the _MDLock structure. We defer the condition notifies + * until right after we unlock the lock. This way the awakened threads + * have a better chance to reaquire the lock. + */ + +#include "primpl.h" + +/* + * AddThreadToCVWaitQueueInternal -- + * + * Add the thread to the end of the condition variable's wait queue. + * The CV's lock must be locked when this function is called. + */ + +static void +AddThreadToCVWaitQueueInternal(PRThread *thred, struct _MDCVar *cv) +{ + PR_ASSERT((cv->waitTail != NULL && cv->waitHead != NULL) + || (cv->waitTail == NULL && cv->waitHead == NULL)); + cv->nwait += 1; + thred->md.inCVWaitQueue = PR_TRUE; + thred->md.next = NULL; + thred->md.prev = cv->waitTail; + if (cv->waitHead == NULL) { + cv->waitHead = thred; + } else { + cv->waitTail->md.next = thred; + } + cv->waitTail = thred; +} + +/* + * md_UnlockAndPostNotifies -- + * + * Unlock the lock, and then do the deferred condition notifies. + * If waitThred and waitCV are not NULL, waitThred is added to + * the wait queue of waitCV before the lock is unlocked. + * + * This function is called by _PR_MD_WAIT_CV and _PR_MD_UNLOCK, + * the two places where a lock is unlocked. + */ +void +md_UnlockAndPostNotifies( + _MDLock *lock, + PRThread *waitThred, + _MDCVar *waitCV) +{ + PRIntn index; + _MDNotified post; + _MDNotified *notified, *prev = NULL; + + /* + * Time to actually notify any conditions that were affected + * while the lock was held. Get a copy of the list that's in + * the lock structure and then zero the original. If it's + * linked to other such structures, we own that storage. + */ + post = lock->notified; /* a safe copy; we own the lock */ + +#if defined(DEBUG) + memset(&lock->notified, 0, sizeof(_MDNotified)); /* reset */ +#else + lock->notified.length = 0; /* these are really sufficient */ + lock->notified.link = NULL; +#endif + + /* + * Figure out how many threads we need to wake up. + */ + notified = &post; /* this is where we start */ + do { + for (index = 0; index < notified->length; ++index) { + _MDCVar *cv = notified->cv[index].cv; + PRThread *thred; + int i; + + /* Fast special case: no waiting threads */ + if (cv->waitHead == NULL) { + notified->cv[index].notifyHead = NULL; + continue; + } + + /* General case */ + if (-1 == notified->cv[index].times) { + /* broadcast */ + thred = cv->waitHead; + while (thred != NULL) { + thred->md.inCVWaitQueue = PR_FALSE; + thred = thred->md.next; + } + notified->cv[index].notifyHead = cv->waitHead; + cv->waitHead = cv->waitTail = NULL; + cv->nwait = 0; + } else { + thred = cv->waitHead; + i = notified->cv[index].times; + while (thred != NULL && i > 0) { + thred->md.inCVWaitQueue = PR_FALSE; + thred = thred->md.next; + i--; + } + notified->cv[index].notifyHead = cv->waitHead; + cv->waitHead = thred; + if (cv->waitHead == NULL) { + cv->waitTail = NULL; + } else { + if (cv->waitHead->md.prev != NULL) { + cv->waitHead->md.prev->md.next = NULL; + cv->waitHead->md.prev = NULL; + } + } + cv->nwait -= notified->cv[index].times - i; + } + } + notified = notified->link; + } while (NULL != notified); + + if (waitThred) { + AddThreadToCVWaitQueueInternal(waitThred, waitCV); + } + + /* Release the lock before notifying */ + DosReleaseMutexSem(lock->mutex); + + notified = &post; /* this is where we start */ + do { + for (index = 0; index < notified->length; ++index) { + PRThread *thred; + PRThread *next; + + thred = notified->cv[index].notifyHead; + while (thred != NULL) { + BOOL rv; + + next = thred->md.next; + thred->md.prev = thred->md.next = NULL; + rv = DosPostEventSem(thred->md.blocked_sema); + PR_ASSERT(rv == NO_ERROR); + thred = next; + } + } + prev = notified; + notified = notified->link; + if (&post != prev) PR_DELETE(prev); + } while (NULL != notified); +} + +/* + * Notifies just get posted to the protecting mutex. The + * actual notification is done when the lock is released so that + * MP systems don't contend for a lock that they can't have. + */ +static void md_PostNotifyToCvar(_MDCVar *cvar, _MDLock *lock, + PRBool broadcast) +{ + PRIntn index = 0; + _MDNotified *notified = &lock->notified; + + while (1) { + for (index = 0; index < notified->length; ++index) { + if (notified->cv[index].cv == cvar) { + if (broadcast) { + notified->cv[index].times = -1; + } else if (-1 != notified->cv[index].times) { + notified->cv[index].times += 1; + } + return; + } + } + /* if not full, enter new CV in this array */ + if (notified->length < _MD_CV_NOTIFIED_LENGTH) break; + + /* if there's no link, create an empty array and link it */ + if (NULL == notified->link) { + notified->link = PR_NEWZAP(_MDNotified); + } + + notified = notified->link; + } + + /* A brand new entry in the array */ + notified->cv[index].times = (broadcast) ? -1 : 1; + notified->cv[index].cv = cvar; + notified->length += 1; +} + +/* + * _PR_MD_NEW_CV() -- Creating new condition variable + * ... Solaris uses cond_init() in similar function. + * + * returns: -1 on failure + * 0 when it succeeds. + * + */ +PRInt32 +_PR_MD_NEW_CV(_MDCVar *cv) +{ + cv->magic = _MD_MAGIC_CV; + /* + * The waitHead, waitTail, and nwait fields are zeroed + * when the PRCondVar structure is created. + */ + return 0; +} + +void _PR_MD_FREE_CV(_MDCVar *cv) +{ + cv->magic = (PRUint32)-1; + return; +} + +/* + * _PR_MD_WAIT_CV() -- Wait on condition variable + */ +void +_PR_MD_WAIT_CV(_MDCVar *cv, _MDLock *lock, PRIntervalTime timeout ) +{ + PRThread *thred = _PR_MD_CURRENT_THREAD(); + ULONG rv, count; + ULONG msecs = (timeout == PR_INTERVAL_NO_TIMEOUT) ? + SEM_INDEFINITE_WAIT : PR_IntervalToMilliseconds(timeout); + + /* + * If we have pending notifies, post them now. + */ + if (0 != lock->notified.length) { + md_UnlockAndPostNotifies(lock, thred, cv); + } else { + AddThreadToCVWaitQueueInternal(thred, cv); + DosReleaseMutexSem(lock->mutex); + } + + /* Wait for notification or timeout; don't really care which */ + rv = DosWaitEventSem(thred->md.blocked_sema, msecs); + if (rv == NO_ERROR) { + DosResetEventSem(thred->md.blocked_sema, &count); + } + + DosRequestMutexSem((lock->mutex), SEM_INDEFINITE_WAIT); + + PR_ASSERT(rv == NO_ERROR || rv == ERROR_TIMEOUT); + + if(rv == ERROR_TIMEOUT) + { + if (thred->md.inCVWaitQueue) { + PR_ASSERT((cv->waitTail != NULL && cv->waitHead != NULL) + || (cv->waitTail == NULL && cv->waitHead == NULL)); + cv->nwait -= 1; + thred->md.inCVWaitQueue = PR_FALSE; + if (cv->waitHead == thred) { + cv->waitHead = thred->md.next; + if (cv->waitHead == NULL) { + cv->waitTail = NULL; + } else { + cv->waitHead->md.prev = NULL; + } + } else { + PR_ASSERT(thred->md.prev != NULL); + thred->md.prev->md.next = thred->md.next; + if (thred->md.next != NULL) { + thred->md.next->md.prev = thred->md.prev; + } else { + PR_ASSERT(cv->waitTail == thred); + cv->waitTail = thred->md.prev; + } + } + thred->md.next = thred->md.prev = NULL; + } else { + /* + * This thread must have been notified, but the + * SemRelease call happens after SemRequest + * times out. Wait on the semaphore again to make it + * non-signaled. We assume this wait won't take long. + */ + rv = DosWaitEventSem(thred->md.blocked_sema, SEM_INDEFINITE_WAIT); + if (rv == NO_ERROR) { + DosResetEventSem(thred->md.blocked_sema, &count); + } + PR_ASSERT(rv == NO_ERROR); + } + } + PR_ASSERT(thred->md.inCVWaitQueue == PR_FALSE); + return; +} /* --- end _PR_MD_WAIT_CV() --- */ + +void +_PR_MD_NOTIFY_CV(_MDCVar *cv, _MDLock *lock) +{ + md_PostNotifyToCvar(cv, lock, PR_FALSE); + return; +} + +PRStatus +_PR_MD_NEW_LOCK(_MDLock *lock) +{ + DosCreateMutexSem(0, &(lock->mutex), 0, 0); + (lock)->notified.length=0; + (lock)->notified.link=NULL; + return PR_SUCCESS; +} + +void +_PR_MD_NOTIFYALL_CV(_MDCVar *cv, _MDLock *lock) +{ + md_PostNotifyToCvar(cv, lock, PR_TRUE); + return; +} + +void _PR_MD_UNLOCK(_MDLock *lock) +{ + if (0 != lock->notified.length) { + md_UnlockAndPostNotifies(lock, NULL, NULL); + } else { + DosReleaseMutexSem(lock->mutex); + } +} |