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/x86/kernel/signal.c

@@ -478,18 +478,8 @@ asmlinkage int
 sys_sigsuspend(int history0, int history1, 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_restore_sigmask();
-	return -ERESTARTNOHAND;
+	return sigsuspend(&blocked);
 }
 
 asmlinkage int