linux-kernel - Re: oops in tracepoint_update_probe_range() (was: Re: [oops -tip] : x86 AMD 64)

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Message-ID: <20090318165407.GA921@elte.hu>
Date:	Wed, 18 Mar 2009 17:54:07 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: oops in tracepoint_update_probe_range() (was: Re: [oops -tip]
	: x86 AMD 64)


* Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:

> On Wed, 2009-03-18 at 17:35 +0100, Ingo Molnar wrote:
> > * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> > 
> > > Good: f4c3c4cdb1de232
> > > Bad : 1e08816af0bc345
> > > 
> > > Config:
> > > http://userweb.kernel.org/~jaswinder/oops_20090318/config-hpdv5-tip-bad-20090318
> > > 
> > > oops:
> > > http://userweb.kernel.org/~jaswinder/oops_20090318/oops_page1.jpg
> > > http://userweb.kernel.org/~jaswinder/oops_20090318/oops_page2.jpg
> > > http://userweb.kernel.org/~jaswinder/oops_20090318/oops_page3.jpg
> > > http://userweb.kernel.org/~jaswinder/oops_20090318/oops_page4.jpg
> > > 
> > > <freeze>
> > 
> > Steve, Frederic - the crashes above are in:
> > 
> > 	tracepoint_update_probe_range()
> > 
> > in a modular kernel apparently.
> > 
> 
> This fixed the oops for me, Is this looks OK to you:
> 
> Subject: [PATCH] x86: tracepoint.c fix oops
> 
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<ffffffff8107d4de>] tracepoint_update_probe_range+0x1f/0x9b
> PGD 13d5fb067 PUD 13d688067 PMD 0
> Oops: 0000 [#1] SMP
> 
> Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> ---
>  kernel/tracepoint.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 7960274..80d1353 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -280,6 +280,8 @@ void tracepoint_update_probe_range(struct tracepoint *begin,
>  
>  	mutex_lock(&tracepoints_mutex);
>  	for (iter = begin; iter < end; iter++) {
> +		if (!iter)
> +			goto out;
>  		mark_entry = get_tracepoint(iter->name);
>  		if (mark_entry) {
>  			set_tracepoint(&mark_entry, iter,
> @@ -288,6 +290,7 @@ void tracepoint_update_probe_range(struct tracepoint *begin,
>  			disable_tracepoint(iter);
>  		}
>  	}
> +out:
>  	mutex_unlock(&tracepoints_mutex);

hm, that does not look right - how can 'iter' become zero? It's a 
text-ish symbol.

I think what we might have here is a corruption of the tracepoint 
data structures.

	Ingo
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