From: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
To: Martijn Coenen <maco-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Vladimir Davydov
<vdavydov-5HdwGun5lf+gSpxsJD1C4w@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 15:56:53 -0500 [thread overview]
Message-ID: <20160115205653.GA26524@cmpxchg.org> (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: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org>
To: Martijn Coenen <maco@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov@virtuozzo.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] memcg: Only free spare array when readers are done
Date: Fri, 15 Jan 2016 15:56:53 -0500 [thread overview]
Message-ID: <20160115205653.GA26524@cmpxchg.org> (raw)
In-Reply-To: <001a113abaa499606605294b5b17@google.com>
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@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org>
To: Martijn Coenen <maco@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov@virtuozzo.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] memcg: Only free spare array when readers are done
Date: Fri, 15 Jan 2016 15:56:53 -0500 [thread overview]
Message-ID: <20160115205653.GA26524@cmpxchg.org> (raw)
In-Reply-To: <001a113abaa499606605294b5b17@google.com>
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@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2016-01-15 20:56 UTC|newest]
Thread overview: 14+ 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
2016-01-14 13:33 ` Martijn Coenen
[not found] ` <001a113abaa499606605294b5b17-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2016-01-14 14:38 ` Michal Hocko
2016-01-14 14:38 ` Michal Hocko
2016-01-14 14:38 ` Michal Hocko
2016-01-14 15:23 ` Martijn Coenen
2016-01-14 15:33 ` Martijn Coenen
2016-01-14 15:33 ` Martijn Coenen
2016-01-15 11:16 ` Vladimir Davydov
2016-01-15 11:16 ` Vladimir Davydov
2016-01-15 11:16 ` Vladimir Davydov
2016-01-15 20:56 ` Johannes Weiner [this message]
2016-01-15 20:56 ` Johannes Weiner
2016-01-15 20:56 ` Johannes Weiner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160115205653.GA26524@cmpxchg.org \
--to=hannes-druugvl0lcnafugrpc6u6w@public.gmane.org \
--cc=cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org \
--cc=maco-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org \
--cc=mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org \
--cc=vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.