Question about ARM function graph tracing
tim.bird at am.sony.com
Fri Feb 4 15:29:25 EST 2011
For a quick update, see below.
On 02/03/2011 08:07 PM, Rabin Vincent wrote:
> On Fri, Feb 4, 2011 at 05:12, Tim Bird <tim.bird at am.sony.com> wrote:
>> I sheepishly admit that I haven't been following mainline very
>> well. �I was happily surprised to see you have mainlined ARMj
>> function graph tracing. �I gave it a test on my old OMAP
>> OSK board, with the results shown below.
> OMAP is missing a notrace annotation on omap_readl():
> Part of that patch was merged through rmk's work, but the
> omap_readl() annotation seems to have been missed.
Yep. It's missing in 2.6.38-rc3.
> Also, if this is OMAP1 and not latest mainline, I think you
> will need a notrace on omap_rev() also (called from inside
> omap_readl() until recently).
I couldn't find that in the sched_clock code paths, but
I 'notrace'd it anyways.
> I think this is most probably what is wrong, since IIRC I saw
> crashes like this on BeagleBoard before I added the notrace on
> omap_readl. Could you please try with these changes?
I have sprinkled 'notrace's liberally throughout the sched_clock
code (including omap_readl() and omap_rev()), and I'm still
seeing problems. I put a recursion guard in
prepare_ftrace_return, and I'm seeing lots of recursion. So
there's still a notrace missing somewhere.
I'm sure this is the problem, so thanks for pointing me in the
right direction. I'll keep trying to pin it down, and let
you know what I find.
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Network Entertainment
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