linux-kernel - Re: [patch] oom: dump stack and VM state when oom killer panics

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Message-Id: <20090921134104.79668479.akpm@linux-foundation.org>
Date:	Mon, 21 Sep 2009 13:41:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	rientjes@...gle.com, kosaki.motohiro@...fujitsu.com,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] oom: dump stack and VM state when oom killer panics

On Fri, 18 Sep 2009 09:26:37 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:

> Hello
> 
> > The oom killer header, including information such as the allocation order
> > and gfp mask, current's cpuset and memory controller, call trace, and VM
> > state information is currently only shown when the oom killer has
> > selected a task to kill.
> > 
> > This information is omitted, however, when the oom killer panics either
> > because of panic_on_oom sysctl settings or when no killable task was
> > found.  It is still relevant to know crucial pieces of information such
> > as the allocation order and VM state when diagnosing such issues,
> > especially at boot.
> > 
> > This patch displays the oom killer header whenever it panics so that bug
> > reports can include pertinent information to debug the issue, if
> > possible.
> > 
> > Signed-off-by: David Rientjes <rientjes@...gle.com>
> 
> Good patch :)
> 
> I have one request. In panic case, I don't hope to call printk_ratelimit().
> the infomation should be displayed always.
> 

The code shouldn't be using printk_ratelimit() - in fact nothing should
be using it and we should remove printk_ratelimit() from the kernel, I
suspect.

Because it uses global state, so a printk_ratelimit() in some random
net driver could cause printks from the oom-killer to be suppressed.

Switching to __ratelimit() would fix such interactions.
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