From: Johannes Weiner <hannes@cmpxchg.org>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 next] memcg: fix deadlock by avoiding stat lock when anon
Date: Thu, 1 Mar 2012 11:00:35 +0100 [thread overview]
Message-ID: <20120301100035.GC1665@cmpxchg.org> (raw)
In-Reply-To: <alpine.LSU.2.00.1202291843120.14002@eggly.anvils>
On Wed, Feb 29, 2012 at 06:44:59PM -0800, Hugh Dickins wrote:
> Fix deadlock in "memcg: use new logic for page stat accounting".
>
> page_remove_rmap() first calls mem_cgroup_begin_update_page_stat(),
> which may take move_lock_mem_cgroup(), unlocked at the end of
> page_remove_rmap() by mem_cgroup_end_update_page_stat().
>
> The PageAnon case never needs to mem_cgroup_dec_page_stat(page,
> MEMCG_NR_FILE_MAPPED); but it often needs to mem_cgroup_uncharge_page(),
> which does lock_page_cgroup(), while holding that move_lock_mem_cgroup().
> Whereas mem_cgroup_move_account() calls move_lock_mem_cgroup() while
> holding lock_page_cgroup().
>
> Since mem_cgroup_begin and end are unnecessary here for PageAnon,
> simply avoid the deadlock and wasted calls in that case.
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
Agreed, let's keep that lock ordering for now, and the comment makes
it clear. Thanks!
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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next prev parent reply other threads:[~2012-03-01 10:00 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-29 5:25 [PATCH 3.3] memcg: fix deadlock by inverting lrucare nesting Hugh Dickins
2012-02-29 5:26 ` [PATCH next] memcg: fix deadlock by avoiding stat lock when anon Hugh Dickins
2012-02-29 19:35 ` Johannes Weiner
2012-03-01 1:18 ` Hugh Dickins
2012-03-01 2:44 ` [PATCH v2 " Hugh Dickins
2012-03-01 9:18 ` KAMEZAWA Hiroyuki
2012-03-01 10:00 ` Johannes Weiner [this message]
2012-02-29 5:28 ` [PATCH next] memcg: remove PCG_FILE_MAPPED fix cosmetic fix Hugh Dickins
2012-02-29 5:40 ` KAMEZAWA Hiroyuki
2012-02-29 19:35 ` Johannes Weiner
2012-02-29 5:30 ` [PATCH next] memcg: remove PCG_CACHE page_cgroup flag fix Hugh Dickins
2012-02-29 5:54 ` KAMEZAWA Hiroyuki
2012-02-29 19:43 ` Johannes Weiner
2012-03-01 1:21 ` Hugh Dickins
2012-03-01 2:42 ` [PATCH next] memcg: remove PCG_CACHE page_cgroup flag fix2 Hugh Dickins
2012-03-01 9:16 ` KAMEZAWA Hiroyuki
2012-02-29 5:39 ` [PATCH 3.3] memcg: fix deadlock by inverting lrucare nesting KAMEZAWA Hiroyuki
2012-02-29 19:00 ` Johannes Weiner
2012-02-29 22:04 ` Andrew Morton
2012-03-01 0:43 ` Hugh Dickins
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