linux-kernel - Re: Kernel Error Message: modprobe used greatest stack depth

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Date:	Wed, 3 Dec 2008 17:03:36 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Peter Teoh" <htmldeveloper@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Kernel Error Message: modprobe used greatest stack depth

Hi Peter.

2008/12/3 Peter Teoh <htmldeveloper@...il.com>:
> In less than 6 hours since I turned on the machine I have been getting
> these message (spread over different times) in my dmesg:
>
> Machine A (AMD Athlon 4200, 3G RAM):
>
> khelper used greatest stack depth: 7484 bytes left
> modprobe used greatest stack depth: 7184 bytes left
> mknod used greatest stack depth: 6976 bytes left
> showconsole used greatest stack depth: 6904 bytes left
> modprobe used greatest stack depth: 5600 bytes left
> mysearch.pl used greatest stack depth: 5536 bytes left
> mysearch.pl used greatest stack depth: 5496 bytes left
> firefox-bin used greatest stack depth: 5484 bytes left
> totem-video-thu used greatest stack depth: 5324 bytes left
> thunderbird-bin used greatest stack depth: 4864 bytes left
>
> And another machine (intel, 3G RAM):
>
> [    0.123030] khelper used greatest stack depth: 2768 bytes left
> [    3.518510] insmod used greatest stack depth: 2148 bytes left
> [    6.203832] insmod used greatest stack depth: 1424 bytes left


This is the result of CONFIG_DEBUG_STACK_USAGE turned on.
When a process exits, kernel/exit.c:check_stack_usage() is called.


> Seemingly harmless, but when it hit firefox, the entire firefox will
> hang - and it does not respond to any keyboard/mouse input.   Since it
> has hit two of my machine simultaneously, I don't it should be
> ignored.



When firefox exits, this function is called... If you think that
check_stack_usage()
could be responsible of this hang, perhaps you can put a printk()
after its call to check it.
I don't know, it depends on when it happens.

>
> Can someone help me?
>
> a.   How do I probe further the cause of the error?
> b.   Seemingly repeatable ..... how to generate a BUG() stack trace at
> the point of error - recompiling really needed?
> c.   Kernel version 2.6.28-rc6, with FTRACE compiled option turned on.
>  HOw do I used FTRACE to de


You should first try to find a way to reproduce it..... When does it happen?
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