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Re: [PATCH RT] kernel/futex: don't deboost too early

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On Fri, 30 Sep 2016 20:43:26 +0200 (CEST)
Thomas Gleixner <tglx@linutronix.de> wrote:

> On Fri, 30 Sep 2016, Steven Rostedt wrote:
> > 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

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[PATCH RT] kernel/futex: don't deboost too early Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-09-30 10:40 +0200
  Re: [PATCH RT] kernel/futex: don't deboost too early Steven Rostedt <rostedt@goodmis.org> - 2016-09-30 18:10 +0200
    Re: [PATCH RT] kernel/futex: don't deboost too early Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-09-30 18:20 +0200
    Re: [PATCH RT] kernel/futex: don't deboost too early Thomas Gleixner <tglx@linutronix.de> - 2016-09-30 20:50 +0200
      Re: [PATCH RT] kernel/futex: don't deboost too early Steven Rostedt <rostedt@goodmis.org> - 2016-10-02 12:10 +0200
        Re: [PATCH RT] kernel/futex: don't deboost too early Thomas Gleixner <tglx@linutronix.de> - 2016-10-03 19:50 +0200

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