[PATCH] x86 spinlock: Fix memory corruption on completing completions

Raghavendra K T
2015-02-08T17:49:33Z

On 02/06/2015 09:55 PM, Linus Torvalds wrote:
> On Fri, Feb 6, 2015 at 6:49 AM, Raghavendra K T
> <raghavendra.kt at linux.vnet.ibm.com> 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).
>

Understood and agreed.

> 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?
>

I have been running several benchmarks (kern, sys, hack, ebizzy etc in
in 1x,2x scenarios. I run them for performance test as well.
(In the current patch I did not get kvm hang in normal run, But
overcommit reproduced it).