linux-kernel - Re: [MEMO] ftrace suckage++

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Message-ID: <20081031020537.GJ21459@tesla>
Date:	Thu, 30 Oct 2008 19:05:37 -0700
From:	"Luis R. Rodriguez" <lrodriguez@...eros.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	"Luis R. Rodriguez" <mcgrof@...il.com>,
	Tim Gardner <tim.gardner@...onical.com>,
	Tomas Winkler <tomasw@...il.com>,
	reinette chatre <reinette.chatre@...ux.intel.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [MEMO] ftrace suckage++

On Thu, Oct 30, 2008 at 06:54:00PM -0700, Steven Rostedt wrote:
> 
> On Thu, 30 Oct 2008, Luis R. Rodriguez wrote:
> 
> > As johannes pointed out to me the culprit to the e1000e corruption was
> > determined to be ftrace related [1]. Well it seems I hit an oops with
> > ftrace using iwlagn after a simple load of the module using
> > wireless-testing. I'm not sure if john's tree yet has ftrace fixes.
> > Both Fedora 10 and Ubuntu 8.10 had dynamic ftrace enabled so users on
> > these first kernels and using compat-wireless may run into this so
> > just putting this out there. I'll can check for this flag in
> > compat-wireless for now and bitch/exit if its enabled unless someone
> > has a better idea.
> >
> > [1] http://lwn.net/Articles/303390/
> >
> > Oops, using wireless-testing and iwlagn with these options enabled:
> >
> > CONFIG_HAVE_FTRACE=y
> > CONFIG_HAVE_DYNAMIC_FTRACE=y
> > CONFIG_FTRACE=y
> > CONFIG_DYNAMIC_FTRACE=y
> >
> 
> Yes, ftrace in 2.6.27 is known to be broken. That's why 2.6.27.1 labeled
> it as such. What is currently in Linus's 2.6.28 git tree is a completely
> rewritten version of the dynamic ftracer, which addresses all of the
> issues that caused breakage in the 2.6.27 release.
> 
> Do not use the 2.6.27 dynamic ftracer, it is known bad. 2.6.28 is fine. If
> you find issues with what is currently in 2.6.28, please let me know.
> There is currently some, "make allyesconfig" breakage that ftrace caused
> on archs other than x86,ppc and sparc, but patches to fix them are
> in queue to Linus.

OK then in that case if *and only if* on 27 and if dynamic tracer is enabled
I'll set compat stuff to simply bail out at compile time.

Thanks,

  Luis
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