linux-kernel - Re: Debugging process hanging in D status and not responding to SIGKILL

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Message-ID: <2c0942db0712210818q1a16291au3b3ddf395867542a@mail.gmail.com>
Date:	Fri, 21 Dec 2007 08:18:50 -0800
From:	"Ray Lee" <ray-lk@...rabbit.org>
To:	"Christian Hammers" <ch@...hspell.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Debugging process hanging in D status and not responding to SIGKILL

On Dec 21, 2007 7:38 AM, Christian Hammers <ch@...hspell.de> wrote:
> Hello
>
> Occasionally all my apache2 processes hang in "D" process status where they are
> no longer responsible to SIGKILL which makes the server almost un-rebootable.
> The processes usually vanish after about 15-30min.
>
> I know that this usually means "I/O wait" somewhere deep inside a kernel
> function where signals are not handled.
>
> But using "strace -p <pid>" I can only see that the last called function is
> flock() (according to /proc/<pid>/fd somebody produced a deadlock when using
> PHP sessions). But flock() normally terminates on SIGTERM and SIGKILL.
>
> Could it be a problem with my SCSI driver who's involed in the flock process?
> The problem usually occurs on two other webserver at the same time, one using
> the same hardware and one being a Dell 6850 with Dell PERC RAID, though.
>
> How can I get further debugging information that could give me a hint?

Do an

   echo t >/proc/sysrq-trigger

and see what it shows.
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