new helper: sigsuspend()

guts of saved_sigmask-based sigsuspend/rt_sigsuspend.  Takes
kernel sigset_t *.

Open-coded instances replaced with calling it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/alpha/kernel/signal.c

@@ -121,17 +121,8 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
 SYSCALL_DEFINE1(sigsuspend, old_sigset_t, mask)
 {
 	sigset_t blocked;
-
-	current->saved_sigmask = current->blocked;
-
-	mask &= _BLOCKABLE;
 	siginitset(&blocked, mask);
-	set_current_blocked(&blocked);
-
-	current->state = TASK_INTERRUPTIBLE;
-	schedule();
-	set_thread_flag(TIF_RESTORE_SIGMASK);
-	return -ERESTARTNOHAND;
+	return sigsuspend(&blocked);
 }
 
 asmlinkage int