[PATCH] kill_pid_info: kill acquired_tasklist_lock

Kill acquired_tasklist_lock, sig_needs_tasklist() is very cheap nowadays.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -1119,19 +1119,18 @@ kill_pg_info(int sig, struct siginfo *info, pid_t pgrp)
 int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
 {
 	int error;
-	int acquired_tasklist_lock = 0;
 	struct task_struct *p;
 
 	rcu_read_lock();
-	if (unlikely(sig_needs_tasklist(sig))) {
+	if (unlikely(sig_needs_tasklist(sig)))
 		read_lock(&tasklist_lock);
-		acquired_tasklist_lock = 1;
-	}
+
 	p = pid_task(pid, PIDTYPE_PID);
 	error = -ESRCH;
 	if (p)
 		error = group_send_sig_info(sig, info, p);
-	if (unlikely(acquired_tasklist_lock))
+
+	if (unlikely(sig_needs_tasklist(sig)))
 		read_unlock(&tasklist_lock);
 	rcu_read_unlock();
 	return error;