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

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Message-ID: <228e2fb7-e141-462c-8796-3cf78aa01902@amd.com>
Date: Mon, 22 Sep 2025 11:27:42 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Prakash Sangappa <prakash.sangappa@...cle.com>, Thomas Gleixner
	<tglx@...utronix.de>
CC: LKML <linux-kernel@...r.kernel.org>, Peter Zijlstra
	<peterz@...radead.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Paul E. McKenney" <paulmck@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
	Jonathan Corbet <corbet@....net>, Madadi Vineeth Reddy
	<vineethr@...ux.ibm.com>, Steven Rostedt <rostedt@...dmis.org>, "Sebastian
 Andrzej Siewior" <bigeasy@...utronix.de>, Arnd Bergmann <arnd@...db.de>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [patch 02/12] rseq: Add fields and constants for time slice
 extension

Hello Prakash,

On 9/22/2025 10:58 AM, Prakash Sangappa wrote:
> With use of a new structure member for slice control, could there be discrepancy 
> with rseq structure size(older version) registered by libc?  In that case the application 
> may  not be able to use slice extension feature unless Libc’s use of rseq is disabled.

In this case, wouldn't GLIBC's rseq registration fail if presumed
__rseq_size is smaller than the "struct rseq" size?

And if it has allocated a large enough area, then the prctl() should
help to query the slice extension feature's availability.

-- 
Thanks and Regards,
Prateek