signals: move handle_stop_signal() into send_signal()

Move handle_stop_signal() into send_signal().  This factors out a couple of
callsites and allows us to do further unifications.

Also, with this change specific_send_sig_info() does handle_stop_signal().
Not that this is really important, we never send STOP/CONT via send_sig() and
friends, but still this looks more consistent.

The only (afaics) special case is get_signal_to_deliver().  If the traced task
dequeues SIGCONT, it can re-send it to itself after ptrace_stop() if the
signal was blocked by debugger.  In that case handle_stop_signal() is
unnecessary, but hopefully not a problem.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -660,8 +660,10 @@ static inline int legacy_queue(struct sigpending *signals, int sig)
 static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
 			struct sigpending *signals)
 {
-	struct sigqueue * q = NULL;
+	struct sigqueue *q;
 
+	assert_spin_locked(&t->sighand->siglock);
+	handle_stop_signal(sig, t);
 	/*
 	 * Short-circuit ignored signals and support queuing
 	 * exactly one non-rt signal, so that we can get more
@@ -766,9 +768,6 @@ specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
 {
 	int ret;
 
-	BUG_ON(!irqs_disabled());
-	assert_spin_locked(&t->sighand->siglock);
-
 	ret = send_signal(sig, info, t, &t->pending);
 	if (ret <= 0)
 		return ret;
@@ -923,9 +922,6 @@ __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
 	int ret;
 
-	assert_spin_locked(&p->sighand->siglock);
-	handle_stop_signal(sig, p);
-
 	/*
 	 * Put this signal on the shared-pending queue, or fail with EAGAIN.
 	 * We always use the shared queue for process-wide signals,
@@ -2241,7 +2237,6 @@ static int do_tkill(int tgid, int pid, int sig)
 		 */
 		if (!error && sig && p->sighand) {
 			spin_lock_irq(&p->sighand->siglock);
-			handle_stop_signal(sig, p);
 			error = specific_send_sig_info(sig, &info, p);
 			spin_unlock_irq(&p->sighand->siglock);
 		}