From: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
To: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Cc: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>,
KAMEZAWA Hiroyuki
<kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>,
Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH] memcg: take reference before releasing rcu_read_lock
Date: Fri, 29 Mar 2013 14:48:42 +0400 [thread overview]
Message-ID: <5155718A.90108@parallels.com> (raw)
In-Reply-To: <51556CE9.9060000-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
On 03/29/2013 02:28 PM, Li Zefan wrote:
> The memcg is not referenced, so it can be destroyed at anytime right
> after we exit rcu read section, so it's not safe to access it.
>
> To fix this, we call css_tryget() to get a reference while we're still
> in rcu read section.
>
> This also removes a bogus comment above __memcg_create_cache_enqueue().
>
Out of curiosity, did you see that happening ?
Theoretically, the race you describe seem real, and the fix is sound.
Acked-by: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
WARNING: multiple messages have this Message-ID (diff)
From: Glauber Costa <glommer@parallels.com>
To: Li Zefan <lizefan@huawei.com>
Cc: Michal Hocko <mhocko@suse.cz>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] memcg: take reference before releasing rcu_read_lock
Date: Fri, 29 Mar 2013 14:48:42 +0400 [thread overview]
Message-ID: <5155718A.90108@parallels.com> (raw)
In-Reply-To: <51556CE9.9060000@huawei.com>
On 03/29/2013 02:28 PM, Li Zefan wrote:
> The memcg is not referenced, so it can be destroyed at anytime right
> after we exit rcu read section, so it's not safe to access it.
>
> To fix this, we call css_tryget() to get a reference while we're still
> in rcu read section.
>
> This also removes a bogus comment above __memcg_create_cache_enqueue().
>
Out of curiosity, did you see that happening ?
Theoretically, the race you describe seem real, and the fix is sound.
Acked-by: Glauber Costa <glommer@parallels.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Glauber Costa <glommer@parallels.com>
To: Li Zefan <lizefan@huawei.com>
Cc: Michal Hocko <mhocko@suse.cz>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>, <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] memcg: take reference before releasing rcu_read_lock
Date: Fri, 29 Mar 2013 14:48:42 +0400 [thread overview]
Message-ID: <5155718A.90108@parallels.com> (raw)
In-Reply-To: <51556CE9.9060000@huawei.com>
On 03/29/2013 02:28 PM, Li Zefan wrote:
> The memcg is not referenced, so it can be destroyed at anytime right
> after we exit rcu read section, so it's not safe to access it.
>
> To fix this, we call css_tryget() to get a reference while we're still
> in rcu read section.
>
> This also removes a bogus comment above __memcg_create_cache_enqueue().
>
Out of curiosity, did you see that happening ?
Theoretically, the race you describe seem real, and the fix is sound.
Acked-by: Glauber Costa <glommer@parallels.com>
next prev parent reply other threads:[~2013-03-29 10:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-29 10:28 [PATCH] memcg: take reference before releasing rcu_read_lock Li Zefan
2013-03-29 10:28 ` Li Zefan
2013-03-29 10:28 ` Li Zefan
[not found] ` <51556CE9.9060000-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-03-29 10:48 ` Glauber Costa [this message]
2013-03-29 10:48 ` Glauber Costa
2013-03-29 10:48 ` Glauber Costa
[not found] ` <5155718A.90108-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2013-03-30 0:35 ` Li Zefan
2013-03-30 0:35 ` Li Zefan
2013-03-30 0:35 ` Li Zefan
2013-04-01 7:24 ` Glauber Costa
2013-04-01 7:24 ` Glauber Costa
2013-03-29 14:59 ` Michal Hocko
2013-03-29 14:59 ` Michal Hocko
2013-03-29 14:59 ` Michal Hocko
2013-04-01 5:03 ` Kamezawa Hiroyuki
2013-04-01 5:03 ` Kamezawa Hiroyuki
2013-04-01 5:03 ` Kamezawa Hiroyuki
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