summaryrefslogtreecommitdiffstats
path: root/nsprpub/pr/src/md/os2/os2cv.c
diff options
context:
space:
mode:
Diffstat (limited to 'nsprpub/pr/src/md/os2/os2cv.c')
-rw-r--r--nsprpub/pr/src/md/os2/os2cv.c334
1 files changed, 334 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 0000000000..91e85c0ebd
--- /dev/null
+++ b/nsprpub/pr/src/md/os2/os2cv.c
@@ -0,0 +1,334 @@
+/* -*- 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);
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-30 14:07:06 +0000