Re: [patch] voluntary-preempt-2.6.8.1-P2

[Ingo Molnar]

* Thomas Charbonnel <thomas@xxxxxxxxxx> wrote:

> When entering check_preempt_timing, preempt_thresh was 0, and
> preempt_max_latency had been freshly reset to 100. It should have
> triggered this code :
>
> 		if (latency < preempt_max_latency)
> 			goto out;
>
> but for some reason it didn't (or there is a problem in the tracing
> code, not showing events that would have increased 'latency').

there is one case where we could 'miss' a new latency: when
/proc/latency_trace is accessed. For the duration of /proc/latency_trace
access, the updating of the max latency is stopped:

        if (down_trylock(&max_mutex))
                goto out;

this is not really a practical problem and fixing it would be quite 
complex.

	Ingo
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