From: Tejun Heo <tj@kernel.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Andrew Morton <akpm@linux-foundation.org>,
Cong Wang <xiyou.wangcong@gmail.com>,
David Rientjes <rientjes@google.com>,
Oleg Nesterov <oleg@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Linux PM list <linux-pm@vger.kernel.org>
Subject: Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend
Date: Tue, 4 Nov 2014 14:27:05 -0500 [thread overview]
Message-ID: <20141104192705.GA22163@htj.dyndns.org> (raw)
In-Reply-To: <20141021142939.GG9415@dhcp22.suse.cz>
Hello,
Sorry about the delay.
On Tue, Oct 21, 2014 at 04:29:39PM +0200, Michal Hocko wrote:
> Reduce the race window by checking all tasks after OOM killer has been
Ugh... this is never a good direction to take. It often just ends up
making bugs harder to reproduce and track down.
> disabled. This is still not race free completely unfortunately because
> oom_killer_disable cannot stop an already ongoing OOM killer so a task
> might still wake up from the fridge and get killed without
> freeze_processes noticing. Full synchronization of OOM and freezer is,
> however, too heavy weight for this highly unlikely case.
Both oom killing and PM freezing are exremely rare events and I have
difficult time why their exclusion would be heavy weight. Care to
elaborate?
Overall, this is a lot of complexity for something which doesn't
really fix the problem and the comments while referring to the race
don't mention that the implemented "fix" is broken, which is pretty
bad as it gives readers of the code a false sense of security and
another hurdle to overcome in actually tracking down what went wrong
if this thing ever shows up as an actual breakage.
I'd strongly recommend implementing something which is actually
correct.
Thanks.
--
tejun
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next prev parent reply other threads:[~2014-11-04 19:27 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-21 7:27 [PATCH 0/4 -v2] OOM vs. freezer interaction fixes Michal Hocko
2014-10-21 7:27 ` [PATCH 1/4] freezer: Do not freeze tasks killed by OOM killer Michal Hocko
2014-10-21 12:04 ` Rafael J. Wysocki
2014-10-21 7:27 ` [PATCH 2/4] freezer: remove obsolete comments in __thaw_task() Michal Hocko
2014-10-21 12:04 ` Rafael J. Wysocki
2014-10-21 7:27 ` [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend Michal Hocko
2014-10-21 12:09 ` Rafael J. Wysocki
2014-10-21 13:14 ` Michal Hocko
2014-10-21 13:42 ` Rafael J. Wysocki
2014-10-21 14:11 ` Michal Hocko
2014-10-21 14:41 ` Rafael J. Wysocki
2014-10-21 14:29 ` Michal Hocko
2014-10-22 14:39 ` Rafael J. Wysocki
2014-10-22 14:22 ` Michal Hocko
2014-10-22 21:18 ` Rafael J. Wysocki
2014-10-26 18:49 ` Pavel Machek
2014-11-04 19:27 ` Tejun Heo [this message]
2014-11-05 12:46 ` Michal Hocko
2014-11-05 13:02 ` Tejun Heo
2014-11-05 13:31 ` Michal Hocko
2014-11-05 13:42 ` Michal Hocko
2014-11-05 14:14 ` Michal Hocko
2014-11-05 15:45 ` Michal Hocko
2014-11-05 15:44 ` Tejun Heo
2014-11-05 16:01 ` Michal Hocko
2014-11-05 16:29 ` Tejun Heo
2014-11-05 16:39 ` Michal Hocko
2014-11-05 16:54 ` Tejun Heo
2014-11-05 17:01 ` Tejun Heo
2014-11-06 13:05 ` Michal Hocko
2014-11-06 15:09 ` Tejun Heo
2014-11-06 16:01 ` Michal Hocko
2014-11-06 16:12 ` Tejun Heo
2014-11-06 16:31 ` Michal Hocko
2014-11-06 16:33 ` Tejun Heo
2014-11-06 16:58 ` Michal Hocko
2014-11-05 17:46 ` Michal Hocko
2014-11-05 17:55 ` Tejun Heo
2014-11-06 12:49 ` Michal Hocko
2014-11-06 15:01 ` Tejun Heo
2014-11-06 16:02 ` Michal Hocko
2014-11-06 16:28 ` Tejun Heo
2014-11-10 16:30 ` Michal Hocko
2014-11-12 18:58 ` [RFC 0/4] OOM vs PM freezer fixes Michal Hocko
2014-11-12 18:58 ` [RFC 1/4] OOM, PM: Do not miss OOM killed frozen tasks Michal Hocko
2014-11-14 17:55 ` Tejun Heo
2014-11-12 18:58 ` [RFC 2/4] OOM, PM: make OOM detection in the freezer path raceless Michal Hocko
2014-11-12 18:58 ` [RFC 3/4] OOM, PM: handle pm freezer as an OOM victim correctly Michal Hocko
2014-11-12 18:58 ` [RFC 4/4] OOM: thaw the OOM victim if it is frozen Michal Hocko
2014-11-14 20:14 ` [RFC 0/4] OOM vs PM freezer fixes Tejun Heo
2014-11-18 21:08 ` Michal Hocko
2014-11-18 21:10 ` [RFC 1/2] oom: add helper for setting and clearing TIF_MEMDIE Michal Hocko
2014-11-18 21:10 ` [RFC 2/2] OOM, PM: make OOM detection in the freezer path raceless Michal Hocko
2014-11-27 0:47 ` Rafael J. Wysocki
2014-12-02 22:08 ` Tejun Heo
2014-12-04 14:16 ` Michal Hocko
2014-12-04 14:44 ` Tejun Heo
2014-12-04 16:56 ` Michal Hocko
2014-12-04 17:18 ` Michal Hocko
2014-12-05 16:41 ` [PATCH 0/4] OOM vs PM freezer fixes Michal Hocko
2014-12-05 16:41 ` [PATCH -v2 1/5] oom: add helpers for setting and clearing TIF_MEMDIE Michal Hocko
2014-12-06 12:56 ` Tejun Heo
2014-12-07 10:13 ` Michal Hocko
2015-01-07 17:57 ` Tejun Heo
2015-01-07 18:23 ` Michal Hocko
2014-12-05 16:41 ` [PATCH -v2 2/5] OOM: thaw the OOM victim if it is frozen Michal Hocko
2014-12-06 13:06 ` Tejun Heo
2014-12-07 10:24 ` Michal Hocko
2014-12-07 10:45 ` Michal Hocko
2014-12-07 13:59 ` Tejun Heo
2014-12-07 18:55 ` Michal Hocko
2014-12-05 16:41 ` [PATCH -v2 3/5] PM: convert printk to pr_* equivalent Michal Hocko
2014-12-05 22:40 ` Rafael J. Wysocki
2014-12-07 10:26 ` Michal Hocko
2014-12-06 13:08 ` Tejun Heo
2014-12-05 16:41 ` [PATCH -v2 4/5] sysrq: " Michal Hocko
2014-12-06 13:09 ` Tejun Heo
2014-12-05 16:41 ` [PATCH -v2 5/5] OOM, PM: make OOM detection in the freezer path raceless Michal Hocko
2014-12-06 13:11 ` Tejun Heo
2014-12-07 10:11 ` Michal Hocko
2015-01-07 18:41 ` Tejun Heo
2015-01-07 18:48 ` Michal Hocko
2015-01-08 11:51 ` Michal Hocko
2014-12-07 10:09 ` [PATCH 0/4] OOM vs PM freezer fixes Michal Hocko
2014-12-07 13:55 ` Tejun Heo
2014-12-07 19:00 ` Michal Hocko
2014-12-18 16:27 ` Michal Hocko
2014-11-05 14:55 ` [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend Michal Hocko
2014-10-26 18:40 ` Pavel Machek
2014-10-21 7:27 ` [PATCH 4/4] PM: convert do_each_thread to for_each_process_thread Michal Hocko
2014-10-21 12:10 ` Rafael J. Wysocki
2014-10-21 13:19 ` Michal Hocko
2014-10-21 13:43 ` Rafael J. Wysocki
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