linux-kernel - Re: Strange system hangs

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Message-ID: <Pine.LNX.4.64.0709291746010.30793@bizon.gios.gov.pl>
Date:	Sat, 29 Sep 2007 17:54:32 +0200 (CEST)
From:	Krzysztof Oledzki <olel@....pl>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Strange system hangs



On Sat, 29 Sep 2007, Nick Piggin wrote:

> On Friday 28 September 2007 18:42, Krzysztof Oledzki wrote:
>> Hello,
>>
>> I am experiencing weird system hangs. Once about 2-5 weeks system freezes
>> and stops accepting remote connections, so it is no longer possible to
>> connect to most important services: smtp (postfix), www (squid) or even
>> ssh. Such connection is accepted but then it hangs.
>>
>> What is strange, that previously established ssh session is usable. It is
>> possible to work on such system until you do something stupid like "less
>> /var/log/all.log". Using strace I found that process blocks on:
>
> Is this a regression? If so, what's the most recent kernel that didn't show
> the problem?

I don't know. First kernel I ran was 2.6.20.x. This is quite fresh system.

> The symptoms could be consistent with some place doing a
> balance_dirty_pages while holding a lock that is required for IO, but I can't
> see a smoking gun (you've got contention on i_mutex, but that should be
> OK).
>
> Can you see if there is any memory under writeback that isn't being
> completed (sysrq+M), also a list the locks held after the hang might be
> helpful (compile in lockdep and sysrq+D)

OK. I'll try to do it next time if there will be a chance. It may take 
some time, BTW.

> Is anything currently running? (sysrq+P and even a full sysrq+T task list
> could be useful).

I'll have to check - maybe I have this captured. If not I'll check it next 
time.

> Are any IO errors occurring at all?

Didn't notice - so no.

Thank you.

Best regards,


 			Krzysztof Olędzki