[PATCH] fix pdeath_signal SMP locking

Obviously almost noone uses the pdeath_signal feature, since this has gone
unnoticed for quite some time.

This patch calls the function that does the right locking for the context
of this call (inside exit_notify).  The names of the signal.c entrypoints
are a little confusing.

include/linux/signal.h

@@ -207,6 +207,7 @@ static inline void init_sigpending(struct sigpending *sig)
 	INIT_LIST_HEAD(&sig->list);
 }
 
+extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p);
 extern long do_sigpending(void __user *, unsigned long);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
 

kernel/exit.c

@@ -529,7 +529,8 @@ static inline void reparent_thread(task_t *p, task_t *father, int traced)
 	p->self_exec_id++;
 
 	if (p->pdeath_signal)
-		send_group_sig_info(p->pdeath_signal, 0, p);
+		/* We already hold the tasklist_lock here.  */
+		group_send_sig_info(p->pdeath_signal, (void *) 0, p);
 
 	/* Move the child from its dying parent to the new one.  */
 	if (unlikely(traced)) {