Measure WaitLatch's timeout parameter in milliseconds, not microseconds.

The original definition had the problem that timeouts exceeding about 2100
seconds couldn't be specified on 32-bit machines.  Milliseconds seem like
sufficient resolution, and finer grain than that would be fantasy anyway
on many platforms.

Back-patch to 9.1 so that this aspect of the latch API won't change between
9.1 and later releases.

Peter Geoghegan

2 files changed, 7 insertions, 10 deletions

diff --git a/src/backend/port/unix_latch.c b/src/backend/port/unix_latch.c
index 950a3a4011..ff4ed8f16c 100644
--- a/src/backend/port/unix_latch.c
+++ b/src/backend/port/unix_latch.c
@@ -137,7 +137,7 @@ DisownLatch(volatile Latch *latch)
  * to wait for. If the latch is already set (and WL_LATCH_SET is given), the
  * function returns immediately.
  *
- * The 'timeout' is given in microseconds. It must be >= 0 if WL_TIMEOUT flag
+ * The 'timeout' is given in milliseconds. It must be >= 0 if WL_TIMEOUT flag
  * is given.  On some platforms, signals cause the timeout to be restarted,
  * so beware that the function can sleep for several times longer than the
  * specified timeout.
@@ -156,6 +156,7 @@ DisownLatch(volatile Latch *latch)
  * have been satisfied. That should be rare in practice, but the caller
  * should not use the return value for anything critical, re-checking the
  * situation with PostmasterIsAlive() or read() on a socket as necessary.
+ * The latch and timeout flag bits can be trusted, however.
  */
 int
 WaitLatch(volatile Latch *latch, int wakeEvents, long timeout)
@@ -191,8 +192,8 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
 	if (wakeEvents & WL_TIMEOUT)
 	{
 		Assert(timeout >= 0);
-		tv.tv_sec = timeout / 1000000L;
-		tv.tv_usec = timeout % 1000000L;
+		tv.tv_sec = timeout / 1000L;
+		tv.tv_usec = (timeout % 1000L) * 1000L;
 		tvp = &tv;
 	}
 
diff --git a/src/backend/port/win32_latch.c b/src/backend/port/win32_latch.c
index eeb85a96ce..10a4006701 100644
--- a/src/backend/port/win32_latch.c
+++ b/src/backend/port/win32_latch.c
@@ -99,7 +99,6 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
 	int			numevents;
 	int			result = 0;
 	int			pmdeath_eventno = 0;
-	long		timeout_ms;
 
 	/* Ignore WL_SOCKET_* events if no valid socket is given */
 	if (sock == PGINVALID_SOCKET)
@@ -110,14 +109,11 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
 	if ((wakeEvents & WL_LATCH_SET) && latch->owner_pid != MyProcPid)
 		elog(ERROR, "cannot wait on a latch owned by another process");
 
-	/* Convert timeout to milliseconds for WaitForMultipleObjects() */
+	/* Convert timeout to form used by WaitForMultipleObjects() */
 	if (wakeEvents & WL_TIMEOUT)
-	{
 		Assert(timeout >= 0);
-		timeout_ms = timeout / 1000;
-	}
 	else
-		timeout_ms = INFINITE;
+		timeout = INFINITE;
 
 	/* Construct an array of event handles for WaitforMultipleObjects() */
 	latchevent = latch->event;
@@ -165,7 +161,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
 			break;
 		}
 
-		rc = WaitForMultipleObjects(numevents, events, FALSE, timeout_ms);
+		rc = WaitForMultipleObjects(numevents, events, FALSE, timeout);
 
 		if (rc == WAIT_FAILED)
 			elog(ERROR, "WaitForMultipleObjects() failed: error code %d", (int) GetLastError());