Optimize semaphore wait with zero timeout on POSIX

minetest · Nov 14, 2019 · 49365b2 · 49365b2
1 parent b5f5e00
commit 49365b2
Showing 1 changed file with 16 additions and 11 deletions.
diff --git a/src/threading/semaphore.cpp b/src/threading/semaphore.cpp
@@ -140,22 +140,27 @@ bool Semaphore::wait(unsigned int time_ms)
 			errno = EINVAL;
 	}
 # else
-	struct timespec wait_time;
-	struct timeval now;
+	int ret;
+	if (time_ms > 0) {
+		struct timespec wait_time;
+		struct timeval now;
 
-	if (gettimeofday(&now, NULL) == -1) {
-		std::cerr << "Semaphore::wait(ms): Unable to get time with gettimeofday!" << std::endl;
-		abort();
-	}
+		if (gettimeofday(&now, NULL) == -1) {
+			std::cerr << "Semaphore::wait(ms): Unable to get time with gettimeofday!" << std::endl;
+			abort();
+		}
 
-	wait_time.tv_nsec = ((time_ms % 1000) * 1000 * 1000) + (now.tv_usec * 1000);
-	wait_time.tv_sec  = (time_ms / 1000) + (wait_time.tv_nsec / (1000 * 1000 * 1000)) + now.tv_sec;
-	wait_time.tv_nsec %= 1000 * 1000 * 1000;
+		wait_time.tv_nsec = ((time_ms % 1000) * 1000 * 1000) + (now.tv_usec * 1000);
+		wait_time.tv_sec  = (time_ms / 1000) + (wait_time.tv_nsec / (1000 * 1000 * 1000)) + now.tv_sec;
+		wait_time.tv_nsec %= 1000 * 1000 * 1000;
 
-	int ret = sem_timedwait(&semaphore, &wait_time);
+		ret = sem_timedwait(&semaphore, &wait_time);
+	} else {
+		ret = sem_trywait(&semaphore);
+	}
 # endif
 
-	assert(!ret || (errno == ETIMEDOUT || errno == EINTR));
+	assert(!ret || (errno == ETIMEDOUT || errno == EINTR || errno == EAGAIN));
 	return !ret;
 #endif
 }