linux-kernel - Re: [BUG] ftrace: available_filter_functions empty after unloading module

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Date:	Thu, 13 Dec 2012 08:34:58 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Piotr Haber <phaber@...adcom.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] ftrace: available_filter_functions empty after unloading
 module

On Mon, 2012-12-10 at 12:45 +0100, Piotr Haber wrote:

> > So you unloaded a module that you were tracing, correct? Hmm, the
> > warning that you hit was an accounting error. The accounting of what
> > functions are traced and what isn't. For some reason it tried to disable
> > a function that wasn't being traced.
> Yes, it happens when i unload a module that i traced before
> 
> > Can you easily reproduce this? If so, can you give my your .config and
> > the steps you used to trigger it.
> Not 100% but it happens often enough to be annoying
> Attached is the config
> As for reproduction, i load the brcmsmac module, add all it symbols to
> set_ftrace_filter, associate with AP and unload the module
> nothing fancy, i use 'function' tracer

Thanks, I'll see if I can reproduce it.

> 
> BTW.
> is it a feature that when there is a traceon trigger added on a function
> from module (like: echo 'brcms_free:traceon' > set_ftrace_filter) after
> module unloading it is not removed?
> just function name gets changed to symbol address

Um, ah, yyyeah! Yeah, yeah, feature. Yep that's a feature alright.

But I think it may be deprecated in the near future.

-- Steve


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