linux-kernel - Re: [PATCH] microblaze: Fix ftrace_update_ftrace

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Message-ID: <4BBAD4BC.3000300@monstr.eu>
Date:	Tue, 06 Apr 2010 08:29:16 +0200
From:	Michal Simek <monstr@...str.eu>
To:	steve@...idescorp.com
CC:	microblaze-uclinux@...e.uq.edu.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] microblaze: Fix ftrace_update_ftrace_func panic

Steven J. Magnani wrote:
> On Mon, 2010-04-05 at 16:26 +0200, Michal Simek wrote:
>> Steven J. Magnani wrote:
>>> The Microblaze dynamic ftrace code assumes a call ordering that is not met
>>> in all scenarios. Specifically, executing a command similar to:
>>>
>>>   echo 105 > /sys/kernel/debug/tracing/set_ftrace_pid
>>>
>>> before any other tracing-related commands results in a kernel panic:
>>>
>>>   BUG: failure at arch/microblaze/kernel/ftrace.c:198/ftrace_update_ftrace_func()!
>>>
>>> Recoding ftrace_update_ftrace_func() to use &ftrace_caller directly eliminates 
>>> the need to capture its address elsewhere (and thus rely on a particular call 
>>> sequence).
>> I would like to replicate this problem to see that there is. I am not 
>> able to reach this fault
>> Please copy & paste log with your commands.
> 

> # echo 80 > /sys/kernel/debug/tracing/set_ftrace_pid
> BUG: failure at
> arch/microblaze/kernel/ftrace.c:202/ftrace_update_ftrace_func()!
> Kernel panic - not syncing: BUG!

I am able to replicate this fault on both versions.
Added to next branch.

Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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