On Fri, 30 Sep 2016 20:43:26 +0200 (CEST)
Thomas Gleixner [off-list ref] wrote:

On Fri, 30 Sep 2016, Steven Rostedt wrote:

quoted

This looks awfully complex. Would something as simple as this work?

What harm can happen by moving the holding of the lock after the
wakeups for RT?  

That's exactly bringing us back to the state before we added the delayed
wakeup so that the woken waiter will not be blocked on hb->lock right
away. That's 2 extra context switches for nothing.

Ah crap, that's the wake up of the owner that's about to grab the lock,
in which case (if on the same CPU) may preempt this guy, just to grab
the hb->lock and block again.

Grumble, how come the easy way is never a possibility :-p

-- Steve