Re: [PATCH v2] tracing/function-graph-tracer: prevent from hrtimer interrupt infinite loop

From: Frédéric Weisbecker
Date: Thu Dec 18 2008 - 16:36:36 EST


2008/12/18 Ingo Molnar <mingo@xxxxxxx>:
>
> * Frédéric Weisbecker <fweisbec@xxxxxxxxx> wrote:
>
>> Hmm. No, I just tested by setting 1000 HZ and disabled NOHZ, the system
>> doesn't lockup unless I turn on the function graph tracer.
>
> but that's what we are interested in: the system locks up with HZ=1000 and
> with the tracer on - right?

Yes.

> Which means that it's not some hrtimer problem, but simply the traced
> timer tick takes more than 1 millisecond to execute under this
> virtualization.
>
> Ingo
>

Oh ok I see. Sorry I'm a bit slow today...
So the solution would be to adapt dynamically the timeout between
hrtimer irq. But I don't know that much hrtimer
to implement such a feature...
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