+2020-07-01 Bruno Haible <bruno@clisp.org>
+
+ pthread-spin: Add error checking.
+ * lib/pthread-spin.c: Include <stdbool.h>.
+ (pthread_spin_init, pthread_spin_lock, pthread_spin_trylock,
+ pthread_spin_unlock) [GCC>=4.7]: Prefer an implementation that verifies
+ the unlocks.
+ * modules/pthread-spin (Depends-on): Add stdbool.
+
2020-07-01 Bruno Haible <bruno@clisp.org>
pthread-spin: Add tests.
/* Specification. */
#include <pthread.h>
+#include <stdbool.h>
+
#if (defined _WIN32 && ! defined __CYGWIN__) && USE_WINDOWS_THREADS
# include "windows-spin.h"
#endif
Documentation:
<https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/_005f_005fatomic-Builtins.html> */
+# if 1
+/* An implementation that verifies the unlocks. */
+
+int
+pthread_spin_init (pthread_spinlock_t *lock,
+ int shared_across_processes _GL_UNUSED)
+{
+ __atomic_store_n ((char *) lock, 0, __ATOMIC_SEQ_CST);
+ return 0;
+}
+
+int
+pthread_spin_lock (pthread_spinlock_t *lock)
+{
+ /* Wait until *lock becomes 0, then replace it with 1. */
+ asyncsafe_spinlock_t zero;
+ while (!(zero = 0,
+ __atomic_compare_exchange_n ((char *) lock, &zero, 1, false,
+ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)))
+ ;
+ return 0;
+}
+
+int
+pthread_spin_trylock (pthread_spinlock_t *lock)
+{
+ asyncsafe_spinlock_t zero;
+ if (!(zero = 0,
+ __atomic_compare_exchange_n ((char *) lock, &zero, 1, false,
+ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)))
+ return EBUSY;
+ return 0;
+}
+
+int
+pthread_spin_unlock (pthread_spinlock_t *lock)
+{
+ /* If *lock is 1, then replace it with 0. */
+ asyncsafe_spinlock_t one = 1;
+ if (!__atomic_compare_exchange_n ((char *) lock, &one, 0, false,
+ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
+ abort ();
+ return 0;
+}
+
+# else
+/* An implementation that is a little bit more optimized, but does not verify
+ the unlocks. */
+
int
pthread_spin_init (pthread_spinlock_t *lock,
int shared_across_processes _GL_UNUSED)
return 0;
}
+# endif
+
int
pthread_spin_destroy (pthread_spinlock_t *lock)
{