Fix WaitLatchOrSocket to handle EOF on socket correctly.

tglsfdc · tglsfdc · commit 31ad6553646c · 2012-05-12T16:36:47.000-04:00
When using poll(), EOF on a socket is reported with the POLLHUP not
POLLIN flag (at least on Linux).  WaitLatchOrSocket failed to check
this bit, causing it to go into a busy-wait loop if EOF occurs.
We earlier fixed the same mistake in the test for the state of the
postmaster_alive socket, but missed it for the caller-supplied socket.
Fortunately, this error is new in 9.2, since 9.1 only had a select()
based code path not a poll() based one.
diff --git a/src/backend/port/unix_latch.c b/src/backend/port/unix_latch.c
@@ -293,7 +293,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
 			result |= WL_TIMEOUT;
 		}
 		if ((wakeEvents & WL_SOCKET_READABLE) &&
-			(pfds[0].revents & POLLIN))
+			(pfds[0].revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
 		{
 			/* data available in socket */
 			result |= WL_SOCKET_READABLE;

Original file line number	Diff line number	Diff line change
`@@ -293,7 +293,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,`
`293`	`293`	`result \|= WL_TIMEOUT;`
`294`	`294`	`}`
`295`	`295`	`if ((wakeEvents & WL_SOCKET_READABLE) &&`
`296`		`- (pfds[0].revents & POLLIN))`
	`296`	`+ (pfds[0].revents & (POLLIN \| POLLHUP \| POLLERR \| POLLNVAL)))`
`297`	`297`	`{`
`298`	`298`	`/* data available in socket */`
`299`	`299`	`result \|= WL_SOCKET_READABLE;`