michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include <kernel/OS.h>
michael@0: 
michael@0: #include "primpl.h"
michael@0: 
michael@0: /*
michael@0: ** Create a new monitor. Monitors are re-entrant locks with a single built-in
michael@0: ** condition variable.
michael@0: **
michael@0: ** This may fail if memory is tight or if some operating system resource
michael@0: ** is low.
michael@0: */
michael@0: PR_IMPLEMENT(PRMonitor*)
michael@0:     PR_NewMonitor (void)
michael@0: {
michael@0:     PRMonitor *mon;
michael@0:     PRCondVar *cvar;
michael@0:     PRLock    *lock;
michael@0: 
michael@0:     mon = PR_NEWZAP( PRMonitor );
michael@0:     if( mon )
michael@0:     {
michael@0: 	lock = PR_NewLock();
michael@0: 	if( !lock )
michael@0:         {
michael@0: 	    PR_DELETE( mon );
michael@0: 	    return( 0 );
michael@0: 	}
michael@0: 
michael@0: 	cvar = PR_NewCondVar( lock );
michael@0: 	if( !cvar )
michael@0: 	{
michael@0: 	    PR_DestroyLock( lock );
michael@0: 	    PR_DELETE( mon );
michael@0: 	    return( 0 );
michael@0: 	}
michael@0: 
michael@0: 	mon->cvar = cvar;
michael@0: 	mon->name = NULL;
michael@0:     }
michael@0: 
michael@0:     return( mon );
michael@0: }
michael@0: 
michael@0: PR_IMPLEMENT(PRMonitor*) PR_NewNamedMonitor(const char* name)
michael@0: {
michael@0:     PRMonitor* mon = PR_NewMonitor();
michael@0:     if( mon )
michael@0:     {
michael@0:         mon->name = name;
michael@0:     }
michael@0:     return mon;
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Destroy a monitor. The caller is responsible for guaranteeing that the
michael@0: ** monitor is no longer in use. There must be no thread waiting on the
michael@0: ** monitor's condition variable and that the lock is not held.
michael@0: **
michael@0: */
michael@0: PR_IMPLEMENT(void)
michael@0:     PR_DestroyMonitor (PRMonitor *mon)
michael@0: {
michael@0:     PR_DestroyLock( mon->cvar->lock );
michael@0:     PR_DestroyCondVar( mon->cvar );
michael@0:     PR_DELETE( mon );
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Enter the lock associated with the monitor. If the calling thread currently
michael@0: ** is in the monitor, the call to enter will silently succeed. In either case,
michael@0: ** it will increment the entry count by one.
michael@0: */
michael@0: PR_IMPLEMENT(void)
michael@0:     PR_EnterMonitor (PRMonitor *mon)
michael@0: {
michael@0:     if( mon->cvar->lock->owner == find_thread( NULL ) )
michael@0:     {
michael@0: 	mon->entryCount++;
michael@0: 
michael@0:     } else
michael@0:     {
michael@0: 	PR_Lock( mon->cvar->lock );
michael@0: 	mon->entryCount = 1;
michael@0:     }
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Decrement the entry count associated with the monitor. If the decremented
michael@0: ** entry count is zero, the monitor is exited. Returns PR_FAILURE if the
michael@0: ** calling thread has not entered the monitor.
michael@0: */
michael@0: PR_IMPLEMENT(PRStatus)
michael@0:     PR_ExitMonitor (PRMonitor *mon)
michael@0: {
michael@0:     if( mon->cvar->lock->owner != find_thread( NULL ) )
michael@0:     {
michael@0: 	return( PR_FAILURE );
michael@0:     }
michael@0:     if( --mon->entryCount == 0 )
michael@0:     {
michael@0: 	return( PR_Unlock( mon->cvar->lock ) );
michael@0:     }
michael@0:     return( PR_SUCCESS );
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Wait for a notify on the monitor's condition variable. Sleep for "ticks"
michael@0: ** amount of time (if "ticks" is PR_INTERVAL_NO_TIMEOUT then the sleep is
michael@0: ** indefinite).
michael@0: **
michael@0: ** While the thread is waiting it exits the monitor (as if it called
michael@0: ** PR_ExitMonitor as many times as it had called PR_EnterMonitor).  When
michael@0: ** the wait has finished the thread regains control of the monitors lock
michael@0: ** with the same entry count as before the wait began.
michael@0: **
michael@0: ** The thread waiting on the monitor will be resumed when the monitor is
michael@0: ** notified (assuming the thread is the next in line to receive the
michael@0: ** notify) or when the "ticks" timeout elapses.
michael@0: **
michael@0: ** Returns PR_FAILURE if the caller has not entered the monitor.
michael@0: */
michael@0: PR_IMPLEMENT(PRStatus)
michael@0:     PR_Wait (PRMonitor *mon, PRIntervalTime ticks)
michael@0: {
michael@0:     PRUint32 entryCount;
michael@0:     PRUintn  status;
michael@0:     PRThread *meThread;
michael@0:     thread_id me = find_thread( NULL );
michael@0:     meThread = PR_GetCurrentThread();
michael@0: 
michael@0:     if( mon->cvar->lock->owner != me ) return( PR_FAILURE );
michael@0: 
michael@0:     entryCount = mon->entryCount;
michael@0:     mon->entryCount = 0;
michael@0: 
michael@0:     status = PR_WaitCondVar( mon->cvar, ticks );
michael@0: 
michael@0:     mon->entryCount = entryCount;
michael@0: 
michael@0:     return( status );
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Notify a thread waiting on the monitor's condition variable. If a thread
michael@0: ** is waiting on the condition variable (using PR_Wait) then it is awakened
michael@0: ** and attempts to reenter the monitor.
michael@0: */
michael@0: PR_IMPLEMENT(PRStatus)
michael@0:     PR_Notify (PRMonitor *mon)
michael@0: {
michael@0:     if( mon->cvar->lock->owner != find_thread( NULL ) )
michael@0:     {
michael@0: 	return( PR_FAILURE );
michael@0:     }
michael@0: 
michael@0:     PR_NotifyCondVar( mon->cvar );
michael@0:     return( PR_SUCCESS );
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Notify all of the threads waiting on the monitor's condition variable.
michael@0: ** All of threads waiting on the condition are scheduled to reenter the
michael@0: ** monitor.
michael@0: */
michael@0: PR_IMPLEMENT(PRStatus)
michael@0:     PR_NotifyAll (PRMonitor *mon)
michael@0: {
michael@0:     if( mon->cvar->lock->owner != find_thread( NULL ) )
michael@0:     {
michael@0: 	return( PR_FAILURE );
michael@0:     }
michael@0: 
michael@0:     PR_NotifyAllCondVar( mon->cvar );
michael@0:     return( PR_SUCCESS );
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** Return the number of times that the current thread has entered the
michael@0: ** lock. Returns zero if the current thread has not entered the lock.
michael@0: */
michael@0: PR_IMPLEMENT(PRIntn)
michael@0:     PR_GetMonitorEntryCount(PRMonitor *mon)
michael@0: {
michael@0:     return( (mon->cvar->lock->owner == find_thread( NULL )) ?
michael@0:             mon->entryCount : 0 );
michael@0: }
michael@0: 
michael@0: /*
michael@0: ** If the current thread is in |mon|, this assertion is guaranteed to
michael@0: ** succeed.  Otherwise, the behavior of this function is undefined.
michael@0: */
michael@0: PR_IMPLEMENT(void)
michael@0:     PR_AssertCurrentThreadInMonitor(PRMonitor *mon)
michael@0: {
michael@0:     PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mon->cvar->lock);
michael@0: }