From: Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
To: Martijn Coenen <maco-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] memcg: Only free spare array when readers are done
Date: Fri, 15 Jan 2016 14:16:23 +0300 [thread overview]
Message-ID: <20160115111623.GA13257@esperanza> (raw)
In-Reply-To: <001a113abaa499606605294b5b17-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
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-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Acked-by: Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
next prev parent reply other threads:[~2016-01-15 11:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 13:33 [PATCH] memcg: Only free spare array when readers are done Martijn Coenen
[not found] ` <001a113abaa499606605294b5b17-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2016-01-14 14:38 ` Michal Hocko
2016-01-14 15:23 ` Martijn Coenen
2016-01-14 15:33 ` Martijn Coenen
2016-01-15 11:16 ` Vladimir Davydov [this message]
2016-01-15 20:56 ` Johannes Weiner
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