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Date: Fri, 15 Jan 2016 15:56:53 -0500 From: Johannes Weiner <hannes@...xchg.org> To: Martijn Coenen <maco@...gle.com> Cc: Michal Hocko <mhocko@...nel.org>, Vladimir Davydov <vdavydov@...tuozzo.com>, cgroups@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] memcg: Only free spare array when readers are done On Thu, Jan 14, 2016 at 02:33:52PM +0100, Martijn Coenen wrote: > A spare array holding mem cgroup threshold events is kept around > to make sure we can always safely deregister an event and have an > array to store the new set of events in. > > In the scenario where we're going from 1 to 0 registered events, the > pointer to the primary array containing 1 event is copied to the spare > slot, and then the spare slot is freed because no events are left. > However, it is freed before calling synchronize_rcu(), which means > readers may still be accessing threshold->primary after it is freed. > > Fixed by only freeing after synchronize_rcu(). > > Signed-off-by: Martijn Coenen <maco@...gle.com> Acked-by: Johannes Weiner <hannes@...xchg.org>
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