linux-kernel - Re: 2.6.26.3 mount process looping on ext3 rw remount

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Message-Id: <20080905112221.8be36263.akpm@linux-foundation.org>
Date:	Fri, 5 Sep 2008 11:22:21 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Marc Haber <mh+linux-kernel@...schlus.de>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.26.3 mount process looping on ext3 rw remount

On Fri, 5 Sep 2008 13:39:02 +0200 Marc Haber <mh+linux-kernel@...schlus.de> wrote:

> On Mon, Aug 25, 2008 at 06:35:28PM -0700, Andrew Morton wrote:
> > Please try to get a kernel profile while it's happening.  oprofile
> > maybe, or just the plain old timer-based profiler.  There's some info
> > in Documentation/basic_profiling.txt.
> 
> I'll boot my next kernel with profile=2.
> 
> > Actually, a simple alternative is to hit sysrq-P five or ten times. 
> > Most of the resulting stack traces will point back at where the CPU is
> > stuck.
> 
> Where are they written to? "P" in a sysrqd telnet session does not
> result in anything being written to the kernel log or to dmesg.

alt-sysrq-p from the attached keyboard.

When operating remotely, use `echo p > /proc/sysrq-trigger'.

The output will be in /var/log/messages and is accessible via
`dmesg -s 1000000'.

Please avoid email client wordwrapping when sending these logs.  99% of
people do this and it makes the text very hard to read.

> > This gets a bit hit-or-miss if you have multiple CPUs, because the
> > sysrq-p trace can land on the wrong CPU.  We recently added a sysrq-l
> > which will generate a trace on all CPUS.
> 
> "l" results in the SysRq HELP being written to the kernel log, so I
> guess that "recently" means "not yet in 2.6.26.3".

ok
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