linux-kernel - Re: ftrace WARNING during boot

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Message-ID: <20091003163645.GI32486@mea-ext.zmailer.org>
Date:	Sat, 3 Oct 2009 19:36:45 +0300
From:	Matti Aarnio <matti.aarnio@...iler.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Matti Aarnio <matti.aarnio@...iler.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: ftrace WARNING during boot

On Sat, Oct 03, 2009 at 11:59:21AM -0400, Steven Rostedt wrote:
> On Sat, 2009-10-03 at 14:28 +0300, Matti Aarnio wrote:
> 
....
> > > >  kernel: ---[ end trace fbf9054ae0f212c7 ]---
> > > >  kernel: ftrace faulted on writing [<ffffffffa0003072>] i2c_new_dummy+0x8/0x5e [i2c_core]
> 
> This means the update to modify the call to mcount to a nop failed.
> Everything else passed (the read and compare). I think I saw some
> patches go by that works on making the text in modules read only.
> 
> The ftrace update for text in core kernel makes the text writable for
> the small window where we call kstop machine and update the text. Then
> it makes that code read only again. At the time this code was written,
> the modules were always read/write. If this has changed, I believe the
> ftrace update needs to be fixed too.

Lattest kernel on Fedora 12 beta series does not have this trouble.
(It has troubles elsewere, but not at ftrace.)

  ACPI: Core revision 20090521
  ftrace: converting mcount calls to 0f 1f 44 00 00
  ftrace: allocating 21030 entries in 83 pages
  Setting APIC routing to flat

> -- Steve

/Matti Aarnio
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