Commit 9cd9be84 authored Dec 20, 2016 by Pavankumar Kondeti

sched: drop related_thread_group_lock before calling call_rcu()



When the last task is removed from a related thread group, the
group is freed by invoking an asynchronous RCU callback. The
call_rcu() can wakeup rcu, kswapd tasks. Hence drop the
related thread group lock, otherwise the wakeup path tries
to acquire the same lock and results in deadlock.

Change-Id: Idfb38a0276edbf6816369b3bab7f21bef5ccc556
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>

parent a3c6f163

kernel/sched/core.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -3964,7 +3964,14 @@ static void remove_task_from_group(struct task_struct *p)

		if (empty_group) {
		list_del(&grp->list);
		/*
		* RCU, kswapd etc tasks can get woken up from
		* call_rcu(). As the wakeup path also acquires
		* the related_thread_group_lock, drop it here.
		*/
		write_unlock(&related_thread_group_lock);
		call_rcu(&grp->rcu, free_related_thread_group);
		write_lock(&related_thread_group_lock);
		}
		}