From: Oleg Nesterov <oleg@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, Andrey Vagin <avagin@openvz.org>
Subject: Re: [patch] oom: prevent unnecessary oom kills or kernel panics
Date: Thu, 10 Mar 2011 13:05:19 +0100 [thread overview]
Message-ID: <20110310120519.GA18415@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1103091222420.13353@chino.kir.corp.google.com>
On 03/09, David Rientjes wrote:
>
> On Wed, 9 Mar 2011, Oleg Nesterov wrote:
>
> > > Using for_each_process() does not consider threads that have failed to
> > > exit after the oom killed parent and, thus, we select another innocent
> > > task to kill when we're really just waiting for those threads to exit
> >
> > How so? select_bad_process() checks TIF_MEMDIE and returns ERR_PTR()
> > if it is set.
> >
>
> TIF_MEMDIE is quite obviously a per-thread flag
Yes, and this is why I think it should be replaced.
> That leader may exit and leave behind several other
> threads
No, it can't.
More precisely, it can, and it can even exit _before_ this process starts
to use a lot of memory, then later this process can be oom-killed.
But, until all threads disappear, the leader can't go away and
for_each_process() must see it.
IOW. If for_each_process() doesn't see the leader, there are no threads
from its thread group. If it does see, the process is not dead yet. It
may be exiting, and the current check tries to detect this case but it
is not perfect. And btw "if (p != current)" code is wrong.
I told this many times. This was one of the reasons why initial ->mm != NULL
in select_bad_process() were completely wrong. Now we are going to re-introduce
them, although Andrey's patch is not that wrong (but should be dropped anyway
imho).
However,
> > And, exactly because we use for_each_process() we do not need to check
> > other threads. The main thread can't disappear until they all exit.
> >
>
> That's obviously false,
I still can't convince you ;)
Oleg.
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next prev parent reply other threads:[~2011-03-10 12:14 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-01 19:09 [patch] oom: prevent unnecessary oom kills or kernel panics David Rientjes
2011-03-03 1:20 ` KOSAKI Motohiro
2011-03-03 19:53 ` David Rientjes
2011-03-06 11:14 ` KOSAKI Motohiro
2011-03-06 22:06 ` David Rientjes
2011-03-08 0:24 ` KOSAKI Motohiro
2011-03-08 2:01 ` KOSAKI Motohiro
2011-03-08 13:42 ` Oleg Nesterov
2011-03-08 23:57 ` David Rientjes
2011-03-09 10:36 ` KOSAKI Motohiro
2011-03-09 11:06 ` Oleg Nesterov
2011-03-09 20:32 ` David Rientjes
2011-03-10 12:05 ` Oleg Nesterov [this message]
2011-03-10 15:40 ` [PATCH 0/1] Was: " Oleg Nesterov
2011-03-10 15:41 ` [PATCH 1/1] oom_kill_task: mark every thread as TIF_MEMDIE Oleg Nesterov
2011-03-13 1:08 ` David Rientjes
2011-03-10 16:36 ` [PATCH 0/1] select_bad_process: improve the PF_EXITING check Oleg Nesterov
2011-03-10 16:37 ` [PATCH 1/1] " Oleg Nesterov
2011-03-10 16:40 ` [PATCH 0/1] " Oleg Nesterov
2011-03-10 17:18 ` [PATCH v2 " Oleg Nesterov
2011-03-10 17:19 ` [PATCH v2 1/1] " Oleg Nesterov
2011-03-13 1:06 ` [patch] oom: prevent unnecessary oom kills or kernel panics David Rientjes
2011-03-09 23:19 ` Andrew Morton
2011-03-11 19:45 ` David Rientjes
2011-03-12 12:34 ` Oleg Nesterov
2011-03-12 13:43 ` [PATCH 0/3] oom: TIF_MEMDIE/PF_EXITING fixes Oleg Nesterov
2011-03-12 13:44 ` [PATCH 1/3] oom: oom_kill_task: mark every thread as TIF_MEMDIE Oleg Nesterov
2011-03-13 1:14 ` David Rientjes
2011-03-12 13:44 ` [PATCH 2/3] oom: select_bad_process: improve the PF_EXITING check Oleg Nesterov
2011-03-12 13:44 ` [PATCH 3/3] oom: select_bad_process: use same_thread_group() Oleg Nesterov
2011-03-12 19:40 ` [PATCH 0/3] oom: TIF_MEMDIE/PF_EXITING fixes Hugh Dickins
2011-03-13 8:53 ` KOSAKI Motohiro
2011-03-13 21:27 ` Oleg Nesterov
2011-03-14 19:04 ` [PATCH 0/3 for 2.6.38] oom: fixes Oleg Nesterov
2011-03-14 19:04 ` [PATCH 1/3 for 2.6.38] oom: oom_kill_process: don't set TIF_MEMDIE if !p->mm Oleg Nesterov
2011-03-14 19:35 ` Linus Torvalds
2011-03-14 20:31 ` Oleg Nesterov
2011-03-14 20:32 ` David Rientjes
2011-03-15 19:12 ` Oleg Nesterov
2011-03-15 19:51 ` David Rientjes
2011-03-14 20:22 ` David Rientjes
2011-03-15 18:53 ` Oleg Nesterov
2011-03-15 19:54 ` David Rientjes
2011-03-15 21:16 ` Oleg Nesterov
2011-03-14 19:05 ` [PATCH 2/3 for 2.6.38] oom: select_bad_process: ignore TIF_MEMDIE zombies Oleg Nesterov
2011-03-14 20:50 ` David Rientjes
2011-03-14 19:05 ` [PATCH 3/3 for 2.6.38] oom: oom_kill_process: fix the child_points logic Oleg Nesterov
2011-03-14 20:41 ` David Rientjes
2011-03-15 19:21 ` Oleg Nesterov
2011-03-13 11:36 ` [PATCH 0/3] oom: TIF_MEMDIE/PF_EXITING fixes KOSAKI Motohiro
2011-03-13 1:11 ` [patch] oom: prevent unnecessary oom kills or kernel panics David Rientjes
2011-03-13 1:15 ` [patch -mm] oom: avoid deferring oom killer if exiting task is being traced David Rientjes
2011-03-14 17:40 ` Oleg Nesterov
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