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Date: Tue, 23 Aug 2016 14:45:19 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Waiman Long <waiman.long@hpe.com>, Jason Low <jason.low2@hpe.com>,
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Subject: Re: [PATCH v4] locking/mutex: Prevent lock starvation when spinning
 is disabled
Message-ID: <20160823124519.GB10138@twins.programming.kicks-ass.net>
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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..