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Diffstat (limited to 'libjava/classpath/gnu/java/awt/peer/gtk/GThreadMutex.java')
-rw-r--r-- | libjava/classpath/gnu/java/awt/peer/gtk/GThreadMutex.java | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/libjava/classpath/gnu/java/awt/peer/gtk/GThreadMutex.java b/libjava/classpath/gnu/java/awt/peer/gtk/GThreadMutex.java new file mode 100644 index 00000000000..e73df9e5509 --- /dev/null +++ b/libjava/classpath/gnu/java/awt/peer/gtk/GThreadMutex.java @@ -0,0 +1,109 @@ +/* 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., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 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: |