From: Tejun Heo <tj@kernel.org>
Date: Fri, 31 May 2019 17:38:57 +0000 (-0700)
Subject: cgroup: Call cgroup_release() before __exit_signal()
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=6b115bf58e6f013ca75e7115aabcbd56c20ff31d;p=openwrt%2Fstaging%2Fblogic.git

cgroup: Call cgroup_release() before __exit_signal()

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>
---

diff --git a/kernel/exit.c b/kernel/exit.c
index 1803efb2922f..a75b6a7f458a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -195,6 +195,7 @@ repeat:
 	rcu_read_unlock();
 
 	proc_flush_task(p);
+	cgroup_release(p);
 
 	write_lock_irq(&tasklist_lock);
 	ptrace_release_task(p);
@@ -220,7 +221,6 @@ repeat:
 	}
 
 	write_unlock_irq(&tasklist_lock);
-	cgroup_release(p);
 	release_thread(p);
 	call_rcu(&p->rcu, delayed_put_task_struct);