sigwait eats blocked default-ignore signals

While a signal is blocked, it must be posted even if its action is
SIG_IGN or is SIG_DFL with the default action to ignore.  This works
right most of the time, but is broken when a sigwait (rt_sigtimedwait)
is in progress.  This changes the early-discard check to respect
real_blocked.  ~blocked is the set to check for "should wake up now",
but ~(blocked|real_blocked) is the set for "blocked" semantics as
defined by POSIX.

This fixes bugzilla entry 9347, see

	http://bugzilla.kernel.org/show_bug.cgi?id=9347Signed-off-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -55,7 +55,7 @@ static int sig_ignored(struct task_struct *t, int sig)
 	 * signal handler may change by the time it is
 	 * unblocked.
 	 */
-	if (sigismember(&t->blocked, sig))
+	if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
 		return 0;
 
 	/* Is it explicitly or implicitly ignored? */