cgroup: Call cgroup_release() before __exit_signal()

commit 6b115bf58e6f013ca75e7115aabcbd56c20ff31d upstream.

cgroup_release() calls cgroup_subsys->release() which is used by the
pids controller to uncharge its pid.  We want to use it to manage
iteration of dying tasks which requires putting it before
__unhash_process().  Move cgroup_release() above __exit_signal().
While this makes it uncharge before the pid is freed, pid is RCU freed
anyway and the window is very narrow.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index 5c0964d..e10de98 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -194,6 +194,7 @@ repeat:
        rcu_read_unlock();
 
        proc_flush_task(p);
+       cgroup_release(p);
 
        write_lock_irq(&tasklist_lock);
        ptrace_release_task(p);
@@ -219,7 +220,6 @@ repeat:
        }
 
        write_unlock_irq(&tasklist_lock);
-       cgroup_release(p);
        release_thread(p);
        call_rcu(&p->rcu, delayed_put_task_struct);