lockfile: convert retry timeout computations to millisecond

When the goal is to wait for some random amount of time up to one
second, it is not necessary to compute with microsecond precision.
This is a preparation to re-use sleep_millisec().

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

lockfile.c

@@ -184,7 +184,7 @@ static int lock_file_timeout(struct lock_file *lk, const char *path,
 {
 	int n = 1;
 	int multiplier = 1;
-	long remaining_us = 0;
+	long remaining_ms = 0;
 	static int random_initialized = 0;
 
 	if (timeout_ms == 0)
@@ -195,16 +195,11 @@ static int lock_file_timeout(struct lock_file *lk, const char *path,
 		random_initialized = 1;
 	}
 
-	if (timeout_ms > 0) {
-		/* avoid overflow */
-		if (timeout_ms <= LONG_MAX / 1000)
-			remaining_us = timeout_ms * 1000;
-		else
-			remaining_us = LONG_MAX;
-	}
+	if (timeout_ms > 0)
+		remaining_ms = timeout_ms;
 
 	while (1) {
-		long backoff_ms, wait_us;
+		long backoff_ms, wait_ms;
 		int fd;
 
 		fd = lock_file(lk, path, flags);
@@ -213,14 +208,14 @@ static int lock_file_timeout(struct lock_file *lk, const char *path,
 			return fd; /* success */
 		else if (errno != EEXIST)
 			return -1; /* failure other than lock held */
-		else if (timeout_ms > 0 && remaining_us <= 0)
+		else if (timeout_ms > 0 && remaining_ms <= 0)
 			return -1; /* failure due to timeout */
 
 		backoff_ms = multiplier * INITIAL_BACKOFF_MS;
 		/* back off for between 0.75*backoff_ms and 1.25*backoff_ms */
-		wait_us = (750 + rand() % 500) * backoff_ms;
-		sleep_microseconds(wait_us);
-		remaining_us -= wait_us;
+		wait_ms = (750 + rand() % 500) * backoff_ms / 1000;
+		sleep_microseconds(wait_ms*1000);
+		remaining_ms -= wait_ms;
 
 		/* Recursion: (n+1)^2 = n^2 + 2n + 1 */
 		multiplier += 2*n + 1;