linux-kernel - Re: Processes hang in an unkillable state

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Message-ID: <20110412182809.GA1218@redhat.com>
Date:	Tue, 12 Apr 2011 20:28:09 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	Robert Święcki <robert@...ecki.net>,
	linux-kernel@...r.kernel.org
Subject: Re: Processes hang in an unkillable state

On 04/12, Américo Wang wrote:
>
> 2011/4/12 Robert Święcki <robert@...ecki.net>:
> > Hi, while fuzzing Linux system calls (32bit fuzzer, 64bi linux
> > kernel), it happens after some time (10-20mins) that some processes
> > enter a state which makes them un-killable. They are either in R or D
> > state.
> >
> > # strace ps wwuax
> > ...
> > ...
> > open("/proc/450/cmdline", O_RDONLY)     = 6
> > read(6,  -             hangs....
> >
> > # kill -9 450
> > # kill -9 450 (no ESRCH)
> >
> > More data in the attachment - I'll keep it in the kdb session for
> > further examination.
>
> http://marc.info/?t.0260440100004
>
> Hmm, it must be stuck at
>
> lib/rwsem.c
>
>         /* wait to be given the lock */
>         for (;;) {
>                 if (!waiter.task)
>                         break;
>                 schedule();
>                 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
>         }
>
> don't know why it still can't acquire the ->mmap_sem...
>
> Cc'ing Oleg...

I seem to understand...

Please wait a bit, I need to recheck.

Oleg.

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