109 lines
4.5 KiB
Java
109 lines
4.5 KiB
Java
/* GThreadMutex.java -- Implements a mutex object for glib's gthread
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abstraction, for use with GNU Classpath's --portable-native-sync option.
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This is used in gthread-jni.c
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Copyright (C) 2004 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.java.awt.peer.gtk;
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/** Implements a mutex object for glib's gthread
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abstraction, for use with GNU Classpath's --portable-native-sync option.
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This is used in gthread-jni.c.
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We use this object to implement the POSIX semantics for Mutexes. They are
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needed are needed for the function vector that is passed to glib's
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g_thread subpackage's initialization function.
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The GThreadMutex object itself serves as the Real Lock; if code has
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entered the monitor for this GThreadMutex object (in Java language, if
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it's synchronized on this object) then it holds the lock that this object
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represents.
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@author Steven Augart
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May, 2004
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*/
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class GThreadMutex
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{
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/** Might "lock" be locked? Is anyone waiting
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to get that lock? How long is the queue?
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If zero, nobody holds a lock on this GThreadMutex object, and nobody is
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trying to get one. Before someone attempts to acquire a lock on this
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object, they must increment potentialLockers. After they release their
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lock on this object, they must decrement potentialLockers.
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Access to this field is guarded by synchronizing on the object
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<code>lockForPotentialLockers</code>.
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After construction, we only access this field via JNI.
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*/
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volatile int potentialLockers;
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/** An object to synchronize to if you want to examine or modify the
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<code>potentialLockers</code> field. Only hold this lock for brief
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moments, just long enough to check or set the value of
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<code>lockForPotentialLockers</code>.
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We use this representation so that g_thread_mutex_trylock() will work
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with the POSIX semantics. This is the only case in which you ever hold a
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lock on <code>lockForPotentialLockers</code> while trying to get another
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lock -- if you are the mutex_trylock() implementation, and you have just
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checked that <code>potentialLockers</code> has the value zero. In that
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case, mutex_trylock() holds the lock on lockForPotentialLockers so that
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another thread calling mutex_trylock() or mutex_lock() won't increment
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potentialLockers after we've checked it and before we've gained the lock
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on the POSIX mutex. Of course, in that case the operation of gaining
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the POSIX lock itself will succeed immediately, and once it has
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succeeded, trylock releases lockForPotentialLockers right away,
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incremented to 1 (one).
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After construction, we only access this field via JNI.
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*/
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Object lockForPotentialLockers;
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GThreadMutex()
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{
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potentialLockers = 0;
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lockForPotentialLockers = new Object();
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}
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}
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// Local Variables:
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// c-file-style: "gnu"
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// End:
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