Re: [Xen-devel] [PATCH] x86 spinlock: Fix memory corruption on completing completions

[Davidlohr Bueso <dave@xxxxxxxxxxxx>]

On Fri, 2015-02-06 at 08:25 -0800, Linus Torvalds wrote:
> On Fri, Feb 6, 2015 at 6:49 AM, Raghavendra K T
> <raghavendra.kt@xxxxxxxxxxxxxxxxxx> wrote:
> > Paravirt spinlock clears slowpath flag after doing unlock.
> [ fix edited out ]
> 
> So I'm not going to be applying this for 3.19, because it's much too
> late and the patch is too scary. Plus the bug probably effectively
> never shows up in real life (it is probably easy to trigger the
> speculative *read* but probably never the actual speculative write
> after dropping the lock last).
> 
> This will need a lot of testing by the paravirt people - both
> performance and correctness. So *maybe* for 3.20, but maybe for even
> later, and then marked for stable, of course.
> 
> Are there any good paravirt stress-tests that people could run for
> extended times?

locktorture inside a VM should give a proper pounding.


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