From: Oleg Nesterov <oleg@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, Andrey Vagin <avagin@openvz.org>
Subject: Re: [patch -mm] oom: avoid deferring oom killer if exiting task is being traced
Date: Mon, 14 Mar 2011 18:40:19 +0100 [thread overview]
Message-ID: <20110314174019.GA14328@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1103121715030.10317@chino.kir.corp.google.com>
On 03/12, David Rientjes wrote:
>
> The oom killer naturally defers killing anything if it finds an eligible
> task that is already exiting and has yet to detach its ->mm. This avoids
> unnecessarily killing tasks when one is already in the exit path and may
> free enough memory that the oom killer is no longer needed. This is
> detected by PF_EXITING since threads that have already detached its ->mm
> are no longer considered at all.
So, this is on top of oom-prevent-unnecessary-oom-kills-or-kernel-panics.patch
I still can't understand which problems that patch tries to solve. Could
you explain why this patch helps in details?
Speaking of "already exiting and has yet to detach its ->mm", did you look
at "[PATCH 2/3] oom: select_bad_process: improve the PF_EXITING check" ?
> The problem with always deferring when a thread is PF_EXITING, however,
> is that it may never actually exit when being traced, specifically if
> another task is tracing it with PTRACE_O_TRACEEXIT. The oom killer does
> not want to defer in this case since there is no guarantee that thread
> will ever exit without intervention.
IOW, you are trying to fight with the test-case I sent,
> + } else {
> + /*
> + * If this task is not being ptraced on exit,
> + * then wait for it to finish before killing
> + * some other task unnecessarily.
> + */
> + if (!(task_ptrace(p->group_leader) &
> + PT_TRACE_EXIT))
> + return ERR_PTR(-1UL);
No, this can't help afaics. It is trivial to change the exploit and
get the same result.
Perhaps I missed something, I didn't read this patch carefully. Will
try to do later.
However. could you please answer my question above?
Also. We have the serious and easily exploitable bugs, I think we
should fix them first. I'll report more details later today.
Oleg.
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prev parent reply other threads:[~2011-03-14 17:49 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
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 [this message]
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