do_poll: return -EINTR when signalled

do_poll() checks signal_pending() but returns 0 when interrupted.  This means
the caller has to check signal_pending() again.

Change it to return -EINTR when signal_pending() and count == 0.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andi Kleen <ak@suse.de>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Vadim Lobanov <vlobanov@speakeasy.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/select.c

@@ -586,7 +586,7 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 	/* Optimise the no-wait case */
 	if (!(*timeout))
 		pt = NULL;
- 
+
 	for (;;) {
 		struct poll_list *walk;
 		long __timeout;
@@ -616,10 +616,12 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 		 * a poll_table to them on the next loop iteration.
 		 */
 		pt = NULL;
-		if (count || !*timeout || signal_pending(current))
-			break;
-		count = wait->error;
-		if (count)
+		if (!count) {
+			count = wait->error;
+			if (signal_pending(current))
+				count = -EINTR;
+		}
+		if (count || !*timeout)
 			break;
 
 		if (*timeout < 0) {
@@ -689,8 +691,6 @@ int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
 
 	poll_initwait(&table);
 	fdcount = do_poll(nfds, head, &table, timeout);
-	if (!fdcount && signal_pending(current))
-		fdcount = -EINTR;
 	poll_freewait(&table);
 
 	for (walk = head; walk; walk = walk->next) {