linux-kernel - Re: 2.6.33 GP fault only when built with tracing

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Date:	Fri, 19 Mar 2010 17:12:53 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	rostedt@...dmis.org
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: 2.6.33 GP fault only when built with tracing

On 03/18/10 16:55, Steven Rostedt wrote:
> On Thu, 2010-03-18 at 16:26 -0700, Randy Dunlap wrote:
>> I can build/boot 2.6.33 with CONFIG_TRACE/TRACING disabled successfully,
>> but when I enable lots of tracing config options and then boot with
>> ftrace=nop on the kernel command line, I see a GP fault when the parport &
>> parport_pc modules are loading/initializing.
> 
> Do you see it without adding the "ftrace=nop"? The only thing that
> should do is expand the ring buffer on boot up.

Yes, it happens with or without "ftrace=nop" as a kernel boot argument.


>>
>> It happens in drivers/parport/share.c::parport_register_device(), when that
>> function calls try_module_get().
>>
>> If I comment out the trace_module_get() calls in include/linux/module.h,
>> the kernel boots with no problems.
> 
> 
> Interesting. Well, trace_module_get() is a TRACE_EVENT tracepoint. But
> should be disabled here. It may be something to do with DEFINE_TRACE. 
> 
> (added Mathieu to Cc since he wrote that code)


-- 
~Randy
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