Re: [RFC][PATCH] preempt: Debug for possible missed preemption checks

From: Peter Zijlstra
Date: Fri Jan 17 2014 - 04:09:19 EST


On Thu, Jan 16, 2014 at 09:12:14PM -0800, Andrew Morton wrote:
> On Thu, 16 Jan 2014 23:57:51 -0500 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> > When PROVE_LOCKING and PREEMPT is configured, the preempt state
> > tracking is active. Testing this out, I added a module that did the
> > following:
>
> So I assume your kernel at least has no instances of this bug, so we
> don't need the patch ;) It *is* a fairly daft thing to do.

Yeah, its exceedingly daft, but I do run into it every so often. Say
once a year or so.

Also, its usually not really a problem on 'normal' kernels, but it
absolutely blows on -rt.
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