Re: [PATCH 1/2] ftrace: Add duration filtering to function graph tracer

[Tim Bird <tim.bird@am.sony.com>]

Steven Rostedt wrote:
> On Mon, 6 Jul 2009, Tim Bird wrote:
>> Another thing I thought of was to not commit the entry event until function
>> exit.  I'm not sure the ring buffer supports having an entry outstanding for
>> long periods of time, though. This would, I believe, hold readers at the entries for
>> the last 'completed' functions, which might solve reader/writer races.
> 
> Heh, I doubt that would be acceptable. The problem is that between reserve 
> and commit, we disable preemption. Thus every function (even the scheduler 
> itself) would have preemption disabled ;-)

Doh!  I think I saw that, but only had a vague recollection of it.
Yeah, that would be a problem ;-)

I'll give the issues some more thought, and see if I can come
up with something.

Thanks for the feedback.
 -- Tim

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Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
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