linux-kernel - Re: [RFC PATCH 0/4] Extend rseq with sched

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Date:   Wed, 17 May 2023 14:36:50 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "H . Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
        linux-api@...r.kernel.org, Christian Brauner <brauner@...nel.org>,
        Florian Weimer <fw@...eb.enyo.de>, David.Laight@...LAB.COM,
        carlos@...hat.com, Peter Oskolkov <posk@...k.io>,
        Alexander Mikhalitsyn <alexander@...alicyn.com>,
        Chris Kennelly <ckennelly@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Darren Hart <dvhart@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        André Almeida <andrealmeid@...lia.com>,
        libc-alpha@...rceware.org, Jonathan Corbet <corbet@....net>
Subject: Re: [RFC PATCH 0/4] Extend rseq with sched_state field

On Wed, 17 May 2023 11:26:50 -0400
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> This prototype extends struct rseq with a new sched_state field, which
> contains a "on-cpu" flag kept up-to-date by the scheduler.
> 
> It is meant to be used by userspace adaptative mutexes to decide between
> busy-wait and futex wait system call (releasing the CPU) behaviors based
> on the current state of the mutex owner.

Woot!

I'm so glad I talked Jon into hanging around for André's spurious talk.
He's the one that brought up rseq (as he mentioned in his article), and I
guess you read that :-)

Unfortunately, I'm in the process of a lot of trips and
meetings/presentations over the next few weeks, and I will not be able to
look into this. But I hope that André could test it out.

Cheers!

-- Steve