On Fri, 2015-02-06 at 16:15 -0500, Sasha Levin wrote:

On 02/06/2015 02:42 PM, Davidlohr Bueso wrote:

quoted

On Fri, 2015-02-06 at 08:25 -0800, Linus Torvalds wrote:

quoted

On Fri, Feb 6, 2015 at 6:49 AM, Raghavendra K T
[off-list ref] wrote:

quoted

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.

Would it catch lifetime issues too? I thought it just tests out correctness.

Given enough contention it should, yeah. The spinlock can be acquired by
another thread right after releasing the lock in the unlock's slowpath.
And all locktorture does is pound on locks with random hold times.

Thanks,
Davidlohr