linux-kernel - RE: console problem?, close(2) hangs /sbin/init

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Date:	Sat, 22 Jan 2011 15:40:25 -0700
From:	John Linn <John.Linn@...inx.com>
To:	Jesper Juhl <jj@...osbits.net>
CC:	<linux-kernel@...r.kernel.org>
Subject: RE: console problem?, close(2) hangs /sbin/init

> -----Original Message-----
> From: Jesper Juhl [mailto:jj@...osbits.net]
> Sent: Saturday, January 22, 2011 3:14 PM
> To: John Linn
> Cc: linux-kernel@...r.kernel.org
> Subject: Re: console problem?, close(2) hangs /sbin/init
> 
> On Sat, 22 Jan 2011, John Linn wrote:
> 
> > I have a kernel that runs fine
> 
> What kernel exactely?
> 
> >with a busybox root file system using
> > inittab.  When I move to a non-busybox init (sysvinit), I see init
> > hanging when doing a close of standard error very early when it
starts.
> > I have debugged it with GDB but not found the source of the hang as
it's
> > in the kernel it appears.

I seems like it's any of the descriptors for the console, 0, 1, or 2 as
I try to isolate it.
Init closes all 3 when it begins and this is where the problem seems to
start.

At one point during some debug, I saw the kernel spit out a message
about a hung task which
showed tty_lock/mutex_lock_slowpath from a sys_open origin.

I had written it off in the beginning because I don't always see it, but
maybe this is also
a symptom I should be debugging.

> >
> > To debug this, I use init=/bin/sh on the kernel command line, then
exec
> > init to start it. The same root file system works on another board
with
> > a different kernel.
> 
> What other kernel version exactely?
> 
> > I have also noticed that building init with
> > INITDEBUG on so that it forks for debugging makes it work fine. This
> > seems to indicate the device nodes are all fine to me.
> >
> > It seems related to PID 1 and the console device.
> >
> > Adding debug to the kernel in sys_close() shows it hanging in
> > filp_close() and I'm still digging more (maybe locking issue). The
> > console is a serial device with a newer driver which I suspected to
be
> > the issue, but can't see anything wrong.
> >
> > Any hints or similar problems seen would be much appreciated.
> > Thanks,
> > John
> >
> 
> --
> Jesper Juhl <jj@...osbits.net>            http://www.chaosbits.net/
> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
> Plain text mails only, please.
> 


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