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Date:      Fri, 21 May 2010 15:39:26 -0700
From:      Carl Johnson <carlj@peak.org>
To:        freebsd-questions@freebsd.org
Subject:   Re: Bash lockups
Message-ID:  <87k4qwswv5.fsf@cjlinux.localnet>
In-Reply-To: <8739xlnhzz.fsf@kobe.laptop> (Giorgos Keramidas's message of "Fri\, 21 May 2010 22\:59\:28 %2B0300")
References:  <877hmzbi1f.fsf@cjlinux.localnet> <878w7d7qbb.fsf@kobe.laptop> <87pr0przea.fsf@cjlinux.localnet> <8739xlnhzz.fsf@kobe.laptop>

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Giorgos Keramidas <keramida@ceid.upatras.gr> writes:

> On Fri, 21 May 2010 09:30:05 -0700, Carl Johnson <carlj@peak.org> wrote:
>> Giorgos Keramidas <keramida@ceid.upatras.gr> writes:
>>> Does this lock-up happen if you leave the shell 'idle' for too long
>>> over an ssh session?  There may be problems with stateful connection
>>> tracking between your terminal and the remote shell :-/
>>
>> No, I don't think that could be the problem.  I am just using ssh
>> between local machines and there is no firewall between them.  It also
>> often seems to happen to a shell as I switch away from it to another
>> one.  One suspicion is that something is sending a signal to the shell
>> as it switches, and bash sometimes doesn't handle that signal
>> properly.
>>
>> I also should have mentioned that I have been running bash as my
>> default shell for years under Linux and have never seen this problem
>> there.
>>
>> Thanks for the suggestion.
>
> That's ok.  If you can attach to the bash process with ktrace please try
> to grab a ktrace file from a deadlocked shell.  We may be able to see
> why it gets deadlocked by running kdump(8) on the shell trace file.
>
> You can run a second shell under ktrace (and hope that the parent
> doesn't deadlock before the traced child shell), by running:
>
>     bash$ ktrace -f bash.trace bash --login
>
> When you exit from the child shell you can dump ktrace(8) events from
> the bash.trace file with:
>
>     bash$ kdump -f bash.trace > logfile 2>&1
>
> Looking near the last records dumped in 'logfile' should be quite
> informative if the process is dead-locked or spinning around the same
> code over and over again.

Thanks for the detailed information.  I have been mostly a linux user,
so this is new for me.  It hasn't been happening very often lately, so
it might be a while now.  I will definitely try to keep any hung
processes around to try your suggestions.

-- 
Carl Johnson		carlj@peak.org




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