linux-kernel - Re: [patch V3 02/12] rseq: Add fields and constants for time slice extension

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Message-ID: <7e44ca0b-e898-4b7f-aaaa-30d8ac52c643@efficios.com>
Date: Fri, 31 Oct 2025 15:31:10 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
 "Paul E. McKenney" <paulmck@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Jonathan Corbet <corbet@....net>,
 Prakash Sangappa <prakash.sangappa@...cle.com>,
 Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
 K Prateek Nayak <kprateek.nayak@....com>,
 Steven Rostedt <rostedt@...dmis.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org
Subject: Re: [patch V3 02/12] rseq: Add fields and constants for time slice
 extension

On 2025-10-29 09:22, Thomas Gleixner wrote:
[...]
> +
> +The thread has to enable the functionality via prctl(2)::
> +
> +    prctl(PR_RSEQ_SLICE_EXTENSION, PR_RSEQ_SLICE_EXTENSION_SET,
> +          PR_RSEQ_SLICE_EXT_ENABLE, 0, 0);

Enabling specifically for each thread requires hooking into thread
creation, and is not a good fit for enabling this from executable or
library constructor function.

What is the use-case for enabling it only for a few threads within
a process rather than for the entire process ?

> +
> +The kernel indicates the grant by clearing rseq::slice_ctrl::reqeust and

reqeust -> request

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com