alpha: take SIGPENDING/NOTIFY_RESUME loop into signal.c

Turn the slow side of work_pending into C function, including all
the looping.  What we get out of that:
	* we do _not_ call get_signal_to_deliver() with IRQs disabled
anymore
	* no need to save/restore volatiles on each pass if there
turns to be more than one (unlikely, but still)
	* all double-restart prevention is in C now.
	* glue gets simpler.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/alpha/kernel/entry.S

@@ -390,15 +390,9 @@ $work_notifysig:
 	bsr	$1, do_switch_stack
 	mov	$sp, $17
 	mov	$5, $18
-	mov	$19, $9		/* save old syscall number */
-	mov	$20, $10	/* save old a3 */
-	and	$5, _TIF_SIGPENDING, $2
-	cmovne	$2, 0, $9	/* we don't want double syscall restarts */
-	jsr	$26, do_notify_resume
-	mov	$9, $19
-	mov	$10, $20
+	jsr	$26, do_work_pending
 	bsr	$1, undo_switch_stack
-	br	ret_to_user
+	br	restore_all
 .end work_pending
 
 /*

arch/alpha/kernel/signal.c

@@ -568,15 +568,24 @@ do_signal(struct pt_regs * regs, struct switch_stack * sw,
 }
 
 void
-do_notify_resume(struct pt_regs *regs, struct switch_stack *sw,
-		 unsigned long thread_info_flags,
+do_work_pending(struct pt_regs *regs, struct switch_stack *sw,
+		 unsigned long thread_flags,
 		 unsigned long r0, unsigned long r19)
 {
-	if (thread_info_flags & _TIF_SIGPENDING)
-		do_signal(regs, sw, r0, r19);
-
-	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
-		clear_thread_flag(TIF_NOTIFY_RESUME);
-		tracehook_notify_resume(regs);
-	}
+	do {
+		if (thread_flags & _TIF_NEED_RESCHED) {
+			schedule();
+		} else {
+			local_irq_enable();
+			if (thread_flags & _TIF_SIGPENDING) {
+				do_signal(regs, sw, r0, r19);
+				r0 = 0;
+			} else {
+				clear_thread_flag(TIF_NOTIFY_RESUME);
+				tracehook_notify_resume(regs);
+			}
+		}
+		local_irq_disable();
+		thread_flags = current_thread_info()->flags;
+	} while (thread_flags & _TIF_WORK_MASK);
 }