linux-kernel - Re: [RFC][PATCH 4/4] futex: Rewrite FUTEX_UNLOCK

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Message-ID: <20161005082102.lm3jze3hzikkzxcg@linutronix.de>
Date:   Wed, 5 Oct 2016 10:21:02 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, tglx@...utronix.de, juri.lelli@....com,
        rostedt@...dmis.org, xlpang@...hat.com,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        jdesfossez@...icios.com, bristot@...hat.com
Subject: Re: [RFC][PATCH 4/4] futex: Rewrite FUTEX_UNLOCK_PI

On 2016-10-05 10:09:12 [+0200], Peter Zijlstra wrote:
> On Wed, Oct 05, 2016 at 09:41:47AM +0200, Sebastian Andrzej Siewior wrote:
> > are those problems DL related?
> 
> One of them, the other is that PI thing you did that ugly nodeboost
> thing for, right?

this no-de-boost yes. This is probably a problem since we have this
"delayed" wake-up. I've been thinking about a marked in PI state to
ignore a de-boost so the spin_unlock() won't be a problem. But if I
understand it right, then this won't solve the DL problem since you
can't have two tasks at the same priority.

Sebastian