linux-kernel - Re: [RFC PATCH 0/7] locking/rtqspinlock: Realtime queued spinlocks

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Date:   Thu, 5 Jan 2017 10:26:37 +0100
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Waiman Long <longman@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC PATCH 0/7] locking/rtqspinlock: Realtime queued spinlocks

On 01/04/2017 04:25 PM, Waiman Long wrote:
>> OK, so a single numerical field isn't sufficient to describe priority
>> anymore, since we added DEADLINE support things have gotten a lot more
>> complex.
> From what I read from the code, DL tasks all have the same priority that
> is higher than any of the RT tasks. So you mean DL tasks have other
> property that kind of categorizing them into different sub-priorities
> that is not being reflected in their priority level. Is that right?

DL tasks are scheduled according to their absolute deadline, which
stored in the u64 curr->dl.deadline.

It is more complex because the priority of a deadline task is always
changing. The priority of a DL task changes on every new
periodic/sporadic replenishment/activation.


-- Daniel