Update to NSPR 4.10.4.

nspr/pr/src/threads/prmon.c

 /* -*- 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;
-        PRCondVar *cvar;
-        PRLock *lock;
+    PRStatus rv;
+
+    if (!_pr_initialized) _PR_ImplicitInitialization();
 
     mon = PR_NEWZAP(PRMonitor);
-    if (mon) {
-                lock = PR_NewLock();
-            if (!lock) {
-                        PR_DELETE(mon);
-                        return 0;
-        }
+    if (mon == NULL) {
+        PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+        return NULL;
+    }
 
-            cvar = PR_NewCondVar(lock);
-            if (!cvar) {
-                PR_DestroyLock(lock);
-                        PR_DELETE(mon);
-                        return 0;
-        }
-        mon->cvar = cvar;
-        mon->name = 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_DestroyLock(mon->cvar->lock);
-    PR_DestroyCondVar(mon->cvar);
-    PR_DELETE(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)
 {
-    if (mon->cvar->lock->owner == _PR_MD_CURRENT_THREAD()) {
-                mon->entryCount++;
-    } else {
-                PR_Lock(mon->cvar->lock);
-                mon->entryCount = 1;
+    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)
 {
-    if (mon->cvar->lock->owner == _PR_MD_CURRENT_THREAD()) {
-                mon->entryCount++;
-                return PR_TRUE;
-    } else {
-                if (PR_TestAndLock(mon->cvar->lock)) {
-                mon->entryCount = 1;
-                        return PR_TRUE;
-                }
+    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;
     }
-    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)
 {
-    if (mon->cvar->lock->owner != _PR_MD_CURRENT_THREAD()) {
+    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;
     }
-    if (--mon->entryCount == 0) {
-                return PR_Unlock(mon->cvar->lock);
+
+    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)
 {
-    return (mon->cvar->lock->owner == _PR_MD_CURRENT_THREAD()) ?
-        mon->entryCount : 0;
+    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
 }
 
 /*
-** If the current thread is in |mon|, this assertion is guaranteed to
-** succeed.  Otherwise, the behavior of this function is undefined.
-*/
-PR_IMPLEMENT(void) PR_AssertCurrentThreadInMonitor(PRMonitor *mon)
-{
-    PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mon->cvar->lock);
-}
-
-/*
 ** 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 if the waiting thread 
+** This routine can return PR_PENDING_INTERRUPT_ERROR if the waiting thread
 ** has been interrupted.
 */
 PR_IMPLEMENT(PRStatus) PR_Wait(PRMonitor *mon, PRIntervalTime ticks)
 {
-    PRUintn entryCount;
-        PRStatus status;
-    PRThread *me = _PR_MD_CURRENT_THREAD();
+    PRStatus rv;
+    PRUint32 saved_entries;
+    PRThread *saved_owner;
 
-    if (mon->cvar->lock->owner != me) return PR_FAILURE;
+    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 */
 
-    entryCount = mon->entryCount;
+    /* 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);
 
-        status = _PR_WaitCondVar(me, mon->cvar, mon->cvar->lock, ticks);
+    rv = PR_WaitCondVar(&mon->waitCV, ticks);
+    PR_ASSERT(rv == PR_SUCCESS);
 
-    mon->entryCount = entryCount;
+    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;
 
-    return status;
+    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)
 {
-    PRThread *me = _PR_MD_CURRENT_THREAD();
-    if (mon->cvar->lock->owner != me) return PR_FAILURE;
-    PR_NotifyCondVar(mon->cvar);
+    _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)
 {
-    PRThread *me = _PR_MD_CURRENT_THREAD();
-    if (mon->cvar->lock->owner != me) return PR_FAILURE;
-    PR_NotifyAllCondVar(mon->cvar);
+    _PR_PostNotifyToMonitor(mon, PR_TRUE);
     return PR_SUCCESS;
 }
 
 /************************************************************************/
 
 PRUint32 _PR_MonitorToString(PRMonitor *mon, char *buf, PRUint32 buflen)
 {
     PRUint32 nb;
 
-    if (mon->cvar->lock->owner) {
+    if (mon->owner) {
         nb = PR_snprintf(buf, buflen, "[%p] owner=%d[%p] count=%ld",
-                         mon, mon->cvar->lock->owner->id,
-                         mon->cvar->lock->owner, mon->entryCount);
+                         mon, mon->owner->id, mon->owner, mon->entryCount);
     } else {
         nb = PR_snprintf(buf, buflen, "[%p]", mon);
     }
     return nb;
 }