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+/* Atomic integers. Useful for testing multithreaded locking primitives.
+ Copyright (C) 2005, 2008-2022 Free Software Foundation, Inc.
+
+ This program 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 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 this program. If not, see <https://www.gnu.org/licenses/>. */
+
+
+/* Whether to use 'volatile' on some variables that communicate information
+ between threads. If set to 0, a semaphore or a lock is used to protect
+ these variables. If set to 1, 'volatile' is used; this is theoretically
+ equivalent but can lead to much slower execution (e.g. 30x slower total
+ run time on a 40-core machine), because 'volatile' does not imply any
+ synchronization/communication between different CPUs. */
+#define USE_VOLATILE 0
+
+#if USE_POSIX_THREADS && HAVE_SEMAPHORE_H
+/* Whether to use a semaphore to communicate information between threads.
+ If set to 0, a lock is used. If set to 1, a semaphore is used.
+ Uncomment this to reduce the dependencies of this test. */
+# define USE_SEMAPHORE 1
+/* Mac OS X provides only named semaphores (sem_open); its facility for
+ unnamed semaphores (sem_init) does not work. */
+# if defined __APPLE__ && defined __MACH__
+# define USE_NAMED_SEMAPHORE 1
+# else
+# define USE_UNNAMED_SEMAPHORE 1
+# endif
+#endif
+
+
+#if USE_SEMAPHORE
+# include <errno.h>
+# include <fcntl.h>
+# include <semaphore.h>
+# include <unistd.h>
+#endif
+
+
+#if USE_VOLATILE
+struct atomic_int {
+ volatile int value;
+};
+static void
+init_atomic_int (struct atomic_int *ai)
+{
+}
+static int
+get_atomic_int_value (struct atomic_int *ai)
+{
+ return ai->value;
+}
+static void
+set_atomic_int_value (struct atomic_int *ai, int new_value)
+{
+ ai->value = new_value;
+}
+#elif USE_SEMAPHORE
+/* This atomic_int implementation can only support the values 0 and 1.
+ It is initially 0 and can be set to 1 only once. */
+# if USE_UNNAMED_SEMAPHORE
+struct atomic_int {
+ sem_t semaphore;
+};
+#define atomic_int_semaphore(ai) (&(ai)->semaphore)
+static void
+init_atomic_int (struct atomic_int *ai)
+{
+ sem_init (&ai->semaphore, 0, 0);
+}
+# endif
+# if USE_NAMED_SEMAPHORE
+struct atomic_int {
+ sem_t *semaphore;
+};
+#define atomic_int_semaphore(ai) ((ai)->semaphore)
+static void
+init_atomic_int (struct atomic_int *ai)
+{
+ sem_t *s;
+ unsigned int count;
+ for (count = 0; ; count++)
+ {
+ char name[80];
+ /* Use getpid() in the name, so that different processes running at the
+ same time will not interfere. Use ai in the name, so that different
+ atomic_int in the same process will not interfere. Use a count in
+ the name, so that even in the (unlikely) case that a semaphore with
+ the specified name already exists, we can try a different name. */
+ sprintf (name, "test-lock-%lu-%p-%u",
+ (unsigned long) getpid (), ai, count);
+ s = sem_open (name, O_CREAT | O_EXCL, 0600, 0);
+ if (s == SEM_FAILED)
+ {
+ if (errno == EEXIST)
+ /* Retry with a different name. */
+ continue;
+ else
+ {
+ perror ("sem_open failed");
+ abort ();
+ }
+ }
+ else
+ {
+ /* Try not to leave a semaphore hanging around on the file system
+ eternally, if we can avoid it. */
+ sem_unlink (name);
+ break;
+ }
+ }
+ ai->semaphore = s;
+}
+# endif
+static int
+get_atomic_int_value (struct atomic_int *ai)
+{
+ if (sem_trywait (atomic_int_semaphore (ai)) == 0)
+ {
+ if (sem_post (atomic_int_semaphore (ai)))
+ abort ();
+ return 1;
+ }
+ else if (errno == EAGAIN)
+ return 0;
+ else
+ abort ();
+}
+static void
+set_atomic_int_value (struct atomic_int *ai, int new_value)
+{
+ if (new_value == 0)
+ /* It's already initialized with 0. */
+ return;
+ /* To set the value 1: */
+ if (sem_post (atomic_int_semaphore (ai)))
+ abort ();
+}
+#else
+struct atomic_int {
+ gl_lock_define (, lock)
+ int value;
+};
+static void
+init_atomic_int (struct atomic_int *ai)
+{
+ gl_lock_init (ai->lock);
+}
+static int
+get_atomic_int_value (struct atomic_int *ai)
+{
+ gl_lock_lock (ai->lock);
+ int ret = ai->value;
+ gl_lock_unlock (ai->lock);
+ return ret;
+}
+static void
+set_atomic_int_value (struct atomic_int *ai, int new_value)
+{
+ gl_lock_lock (ai->lock);
+ ai->value = new_value;
+ gl_lock_unlock (ai->lock);
+}
+#endif