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-Tag: v4.14.138~6
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d7b538a6c9678fcc6f00b6024bcbfd4bb0593d1c;p=users%2Fdwmw2%2Flinux.git

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 95ce231ff5e24..15437cfdcd70d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -193,6 +193,7 @@ repeat:
 	rcu_read_unlock();
 
 	proc_flush_task(p);
+	cgroup_release(p);
 
 	write_lock_irq(&tasklist_lock);
 	ptrace_release_task(p);
@@ -218,7 +219,6 @@ repeat:
 	}
 
 	write_unlock_irq(&tasklist_lock);
-	cgroup_release(p);
 	release_thread(p);
 	call_rcu(&p->rcu, delayed_put_task_struct);