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authorrpj <rpj>2002-02-11 01:53:22 +0000
committerrpj <rpj>2002-02-11 01:53:22 +0000
commite6f1797e9e9925ae7f9dda54806ef8f52ae3ed07 (patch)
treec513bf622584d48383ce9d167159c81baa71b3f9 /condvar_check_need_init.c
parent1cf6fdda9842e5b728cdce93683292f4380a4572 (diff)
Splitting files. See ChangeLog file for details.
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+/*
+ * condvar_check_need_init.c
+ *
+ * Description:
+ * This translation unit implements condition variables and their primitives.
+ *
+ *
+ * --------------------------------------------------------------------------
+ *
+ * Pthreads-win32 - POSIX Threads Library for Win32
+ * Copyright(C) 1998 John E. Bossom
+ * Copyright(C) 1999,2002 Pthreads-win32 contributors
+ *
+ * Contact Email: rpj@ise.canberra.edu.au
+ *
+ * The current list of contributors is contained
+ * in the file CONTRIBUTORS included with the source
+ * code distribution. The list can also be seen at the
+ * following World Wide Web location:
+ * http://sources.redhat.com/pthreads-win32/contributors.html
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library in the file COPYING.LIB;
+ * if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include "pthread.h"
+#include "implement.h"
+
+
+static INLINE int
+ptw32_cond_check_need_init (pthread_cond_t *cond)
+{
+ int result = 0;
+
+ /*
+ * The following guarded test is specifically for statically
+ * initialised condition variables (via PTHREAD_OBJECT_INITIALIZER).
+ *
+ * Note that by not providing this synchronisation we risk
+ * introducing race conditions into applications which are
+ * correctly written.
+ *
+ * Approach
+ * --------
+ * We know that static condition variables will not be PROCESS_SHARED
+ * so we can serialise access to internal state using
+ * Win32 Critical Sections rather than Win32 Mutexes.
+ *
+ * If using a single global lock slows applications down too much,
+ * multiple global locks could be created and hashed on some random
+ * value associated with each mutex, the pointer perhaps. At a guess,
+ * a good value for the optimal number of global locks might be
+ * the number of processors + 1.
+ *
+ */
+ EnterCriticalSection(&ptw32_cond_test_init_lock);
+
+ /*
+ * We got here possibly under race
+ * conditions. Check again inside the critical section.
+ * If a static cv has been destroyed, the application can
+ * re-initialise it only by calling pthread_cond_init()
+ * explicitly.
+ */
+ if (*cond == PTHREAD_COND_INITIALIZER)
+ {
+ result = pthread_cond_init(cond, NULL);
+ }
+ else if (*cond == NULL)
+ {
+ /*
+ * The cv has been destroyed while we were waiting to
+ * initialise it, so the operation that caused the
+ * auto-initialisation should fail.
+ */
+ result = EINVAL;
+ }
+
+ LeaveCriticalSection(&ptw32_cond_test_init_lock);
+
+ return result;
+}