Re: [PATCH 2/3 v2] futex: avoid double wake up in futex_wake() on -RT

From: Peter Zijlstra
Date: Thu Apr 16 2015 - 06:17:04 EST


On Thu, Apr 16, 2015 at 11:19:41AM +0200, Thomas Gleixner wrote:
> So any code which does not handle a spurious wakeup is broken
> independent of the futex changes. So really nothing to worry about.

Back when we did this:

http://lkml.iu.edu/hypermail/linux/kernel/1109.1/01941.html
http://lkml.iu.edu/hypermail/linux/kernel/1109.1/01943.html

Things came apart -- notably sysvsems.

And yes its true that anything not dealing with spuriuos wakups is
borken, but there's still quite a lot of borken out there, although I
think we fixed all the really common ones.

But if we decide we want to go do this, I'd propose we reintroduce this
delayed wake list thing again.
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