| /* GThreadMutex.java -- Implements a mutex object for glib's gthread |
| abstraction, for use with GNU Classpath's --portable-native-sync option. |
| This is used in gthread-jni.c |
| |
| Copyright (C) 2004 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package gnu.java.awt.peer.gtk; |
| |
| /** Implements a mutex object for glib's gthread |
| abstraction, for use with GNU Classpath's --portable-native-sync option. |
| This is used in gthread-jni.c. |
| |
| We use this object to implement the POSIX semantics for Mutexes. They are |
| needed are needed for the function vector that is passed to glib's |
| g_thread subpackage's initialization function. |
| |
| The GThreadMutex object itself serves as the Real Lock; if code has |
| entered the monitor for this GThreadMutex object (in Java language, if |
| it's synchronized on this object) then it holds the lock that this object |
| represents. |
| |
| @author Steven Augart |
| May, 2004 |
| |
| |
| */ |
| |
| class GThreadMutex |
| { |
| /** Might "lock" be locked? Is anyone waiting |
| to get that lock? How long is the queue? |
| |
| If zero, nobody holds a lock on this GThreadMutex object, and nobody is |
| trying to get one. Before someone attempts to acquire a lock on this |
| object, they must increment potentialLockers. After they release their |
| lock on this object, they must decrement potentialLockers. |
| |
| Access to this field is guarded by synchronizing on the object |
| <code>lockForPotentialLockers</code>. |
| |
| After construction, we only access this field via JNI. |
| */ |
| volatile int potentialLockers; |
| |
| /** An object to synchronize to if you want to examine or modify the |
| <code>potentialLockers</code> field. Only hold this lock for brief |
| moments, just long enough to check or set the value of |
| <code>lockForPotentialLockers</code>. |
| |
| We use this representation so that g_thread_mutex_trylock() will work |
| with the POSIX semantics. This is the only case in which you ever hold a |
| lock on <code>lockForPotentialLockers</code> while trying to get another |
| lock -- if you are the mutex_trylock() implementation, and you have just |
| checked that <code>potentialLockers</code> has the value zero. In that |
| case, mutex_trylock() holds the lock on lockForPotentialLockers so that |
| another thread calling mutex_trylock() or mutex_lock() won't increment |
| potentialLockers after we've checked it and before we've gained the lock |
| on the POSIX mutex. Of course, in that case the operation of gaining |
| the POSIX lock itself will succeed immediately, and once it has |
| succeeded, trylock releases lockForPotentialLockers right away, |
| incremented to 1 (one). |
| |
| After construction, we only access this field via JNI. |
| */ |
| Object lockForPotentialLockers; |
| |
| GThreadMutex() |
| { |
| potentialLockers = 0; |
| lockForPotentialLockers = new Object(); |
| } |
| } |
| // Local Variables: |
| // c-file-style: "gnu" |
| // End: |