Re: [PATCH v4] locking/mutex: Prevent lock starvation when spinning is disabled

Peter Zijlstra
2016-08-23T12:45:53Z

On Fri, Aug 19, 2016 at 12:45:27PM -0700, Linus Torvalds wrote:
> On Fri, Aug 19, 2016 at 12:33 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > That seems more messy to me..
>
> Can't we just say that we always spin? Are there any really valid
> cases where spinning isn't ok?
>
> We've historically disabled spinning when mutex debugging is enabled,
> but since the spinning is limited anyway, couldn't we just spin even
> with debugging enabled?
>
> I hate how these patches are trying to solve a problem that doesn't
> even happen under normal circumstances, and add special-case code for
> something that is already a special-case condition. So rather than
> adding even more special cases, could we look at _removing_ the
> special cases that cause problems instead?

So I think I have a bunch of patches that solves the fundamental issues,
_However_... they're quite invasive and would need some serious
benchmarking.

I'll post them in a separate thread as RFC..