!978 Optimize sem_timedwait performance

Merge pull request !978 from qijinquan/sem_timedwait

musl_src.gni

@@ -2223,6 +2223,7 @@ musl_src_porting_file = [
   "src/aio/aio.c",
   "src/misc/aarch64/syscall.s",
   "src/stdlib/strtod.c",
+  "src/thread/sem_timedwait.c",
   "src/stdio/vfscanf.c",
   "src/stdio/fileno.c",
 ]

porting/linux/user/src/thread/sem_timedwait.c

+#include <semaphore.h>
+#include "pthread_impl.h"
+
+static void cleanup(void *p)
+{
+	a_dec(p);
+}
+int __sem_timedwait(sem_t *restrict sem, const struct timespec *restrict at)
+{
+	int spins = 100;
+	while (spins-- && sem->__val[0] <= 0 && !sem->__val[1]) a_spin();
+
+	while (sem_trywait(sem)) {
+		int r;
+		a_inc(sem->__val+1);
+		a_cas(sem->__val, 0, -1);
+		pthread_cleanup_push(cleanup, (void *)(sem->__val+1));
+		r = __timedwait_cp(sem->__val, -1, CLOCK_REALTIME, at, sem->__val[2]);
+		pthread_cleanup_pop(1);
+		if (r) {
+			errno = r;
+			return -1;
+		}
+	}
+	return 0;
+}
+int sem_timedwait(sem_t *restrict sem, const struct timespec *restrict at)
+{
+	pthread_testcancel();
+
+	if (!sem_trywait(sem)) return 0;
+
+	return __sem_timedwait(sem, at);
+}