[PATCH] RCU signal handling

made this BUG_ON() unsafe. This code runs under ->siglock,
while switch_exec_pids() takes tasklist_lock.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kernel/signal.c

@@ -975,7 +975,6 @@ __group_complete_signal(int sig, struct task_struct *p)
 		if (t == NULL)
 			/* restart balancing at this thread */
 			t = p->signal->curr_target = p;
-		BUG_ON(t->tgid != p->tgid);
 
 		while (!wants_signal(sig, t)) {
 			t = next_thread(t);