From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH -v2 3/6] memcg: mm == NULL is not allowed for mem_cgroup_try_charge_mm
Date: Tue, 4 Feb 2014 11:05:58 -0500 [thread overview]
Message-ID: <20140204160558.GO6963@cmpxchg.org> (raw)
In-Reply-To: <1391520540-17436-4-git-send-email-mhocko@suse.cz>
On Tue, Feb 04, 2014 at 02:28:57PM +0100, Michal Hocko wrote:
> An ancient comment tries to explain that a given mm might be NULL when a
> task is migrated. It has been introduced by 8a9f3ccd (Memory controller:
> memory accounting) along with other bigger changes so it is not much
> more specific about the conditions.
>
> Anyway, Even if the task is migrated to another memcg there is no way we
> can see NULL mm struct. So either this was not correct from the very
> beginning or it is not true anymore.
> The only remaining case would be seeing charges after exit_mm but that
> would be a bug on its own as the task doesn't have an address space
> anymore.
>
> This patch replaces the check by VM_BUG_ON to make it obvious that we
> really expect non-NULL mm_struct.
>
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH -v2 3/6] memcg: mm == NULL is not allowed for mem_cgroup_try_charge_mm
Date: Tue, 4 Feb 2014 11:05:58 -0500 [thread overview]
Message-ID: <20140204160558.GO6963@cmpxchg.org> (raw)
In-Reply-To: <1391520540-17436-4-git-send-email-mhocko@suse.cz>
On Tue, Feb 04, 2014 at 02:28:57PM +0100, Michal Hocko wrote:
> An ancient comment tries to explain that a given mm might be NULL when a
> task is migrated. It has been introduced by 8a9f3ccd (Memory controller:
> memory accounting) along with other bigger changes so it is not much
> more specific about the conditions.
>
> Anyway, Even if the task is migrated to another memcg there is no way we
> can see NULL mm struct. So either this was not correct from the very
> beginning or it is not true anymore.
> The only remaining case would be seeing charges after exit_mm but that
> would be a bug on its own as the task doesn't have an address space
> anymore.
>
> This patch replaces the check by VM_BUG_ON to make it obvious that we
> really expect non-NULL mm_struct.
>
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2014-02-04 16:06 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-04 13:28 [PATCH -v2 0/6] memcg: some charge path cleanups + css offline vs. charge race fix Michal Hocko
2014-02-04 13:28 ` Michal Hocko
2014-02-04 13:28 ` [PATCH -v2 1/6] memcg: do not replicate try_get_mem_cgroup_from_mm in __mem_cgroup_try_charge Michal Hocko
2014-02-04 13:28 ` Michal Hocko
2014-02-04 15:55 ` Johannes Weiner
2014-02-04 15:55 ` Johannes Weiner
2014-02-04 16:05 ` Michal Hocko
2014-02-04 16:05 ` Michal Hocko
2014-02-05 13:49 ` Michal Hocko
2014-02-05 13:49 ` Michal Hocko
2014-02-04 13:28 ` [PATCH -v2 2/6] memcg: cleanup charge routines Michal Hocko
2014-02-04 13:28 ` Michal Hocko
2014-02-04 16:05 ` Johannes Weiner
2014-02-04 16:05 ` Johannes Weiner
2014-02-04 16:12 ` Michal Hocko
2014-02-04 16:12 ` Michal Hocko
2014-02-04 16:40 ` Johannes Weiner
2014-02-04 16:40 ` Johannes Weiner
2014-02-04 19:11 ` Michal Hocko
2014-02-04 19:11 ` Michal Hocko
2014-02-04 19:36 ` Johannes Weiner
2014-02-04 19:36 ` Johannes Weiner
2014-02-04 13:28 ` [PATCH -v2 3/6] memcg: mm == NULL is not allowed for mem_cgroup_try_charge_mm Michal Hocko
2014-02-04 13:28 ` Michal Hocko
2014-02-04 16:05 ` Johannes Weiner [this message]
2014-02-04 16:05 ` Johannes Weiner
2014-02-04 13:28 ` [PATCH -v2 4/6] memcg: make sure that memcg is not offline when charging Michal Hocko
2014-02-04 13:28 ` Michal Hocko
2014-02-04 16:29 ` Johannes Weiner
2014-02-04 16:29 ` Johannes Weiner
2014-02-05 13:38 ` Michal Hocko
2014-02-05 13:38 ` Michal Hocko
2014-02-05 15:28 ` Johannes Weiner
2014-02-05 15:28 ` Johannes Weiner
2014-02-05 15:42 ` Tejun Heo
2014-02-05 15:42 ` Tejun Heo
2014-02-05 16:19 ` Michal Hocko
2014-02-05 16:19 ` Michal Hocko
2014-02-05 16:29 ` Michal Hocko
2014-02-05 16:29 ` Michal Hocko
2014-02-05 16:30 ` Tejun Heo
2014-02-05 16:30 ` Tejun Heo
2014-02-05 16:45 ` Johannes Weiner
2014-02-05 16:45 ` Johannes Weiner
2014-02-05 17:23 ` Michal Hocko
2014-02-05 17:23 ` Michal Hocko
2014-02-04 13:28 ` [PATCH -v2 5/6] memcg, kmem: clean up memcg parameter handling Michal Hocko
2014-02-04 13:28 ` Michal Hocko
2014-02-04 16:32 ` Johannes Weiner
2014-02-04 16:32 ` Johannes Weiner
2014-02-04 16:42 ` Michal Hocko
2014-02-04 16:42 ` Michal Hocko
2014-02-04 13:29 ` [PATCH -v2 6/6] Revert "mm: memcg: fix race condition between memcg teardown and swapin" Michal Hocko
2014-02-04 13:29 ` Michal Hocko
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