linux-kernel - Re: [PATCH -v2 3/9] sched/deadline/rtmutex: Dont miss the dl_runtime/dl

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Date:   Thu, 29 Sep 2016 10:48:13 -0400 (EDT)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     mingo@...nel.org, juri.lelli@....com, rostedt@...dmis.org,
        xlpang@...hat.com, bigeasy@...utronix.de,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        jdesfossez@...icios.com, bristot@...hat.com,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH -v2 3/9] sched/deadline/rtmutex: Dont miss the
 dl_runtime/dl_period update

On Mon, 26 Sep 2016, Peter Zijlstra wrote:

> Currently dl tasks will actually return at the very beginning
> of rt_mutex_adjust_prio_chain() in !detect_deadlock cases:
> 
>     if (waiter->prio == task->prio) {
>         if (!detect_deadlock)
>             goto out_unlock_pi; // out here
>         else
>             requeue = false;
>     }
> 
> As the deadline value of blocked deadline tasks(waiters) without
> changing their sched_class(thus prio doesn't change) never changes,
> this seems reasonable, but it actually misses the chance of updating
> rt_mutex_waiter's "dl_runtime(period)_copy" if a waiter updates its
> deadline parameters(dl_runtime, dl_period) or boosted waiter changes
> to !deadline class.
> 
> Thus, force deadline task not out by adding the !dl_prio() condition.

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>