signals: check_kill_permission: remove tasklist_lock

Now that task_session() can't return a false NULL, check_kill_permission()
doesn't need tasklist_lock.

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>

diff --git a/kernel/signal.c b/kernel/signal.c
index 24be82c..02ef354 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -551,9 +551,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
            !capable(CAP_KILL)) {
                switch (sig) {
                case SIGCONT:
-                       read_lock(&tasklist_lock);
                        sid = task_session(t);
-                       read_unlock(&tasklist_lock);
                        /*
                         * We don't return the error if sid == NULL. The
                         * task was unhashed, the caller must notice this.