Initial version

1 files changed, 13 insertions, 0 deletions

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
new file mode 100644
index 0000000..beb435d
--- /dev/null
+++ b/src/thread/sem_trywait.c
@@ -0,0 +1,13 @@
+#include <semaphore.h>
+#include <limits.h>
+#include "pthread_impl.h"
+
+int sem_trywait(sem_t *sem)
+{
+	int val;
+	while ((val=sem->__val[0]) & SEM_VALUE_MAX) {
+		if (a_cas(sem->__val, val, val-1)==val) return 0;
+	}
+	errno = EAGAIN;
+	return -1;
+}