linux-kernel - Re: [patch 06/12] rseq: Implement sys_rseq_slice

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Message-ID: <e61943a6-0005-4146-a5bd-485d3b32e709@amd.com>
Date: Wed, 10 Sep 2025 16:45:01 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
CC: Arnd Bergmann <arnd@...db.de>, <linux-arch@...r.kernel.org>, Peter Zilstra
	<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>, Prakash Sangappa
	<prakash.sangappa@...cle.com>, Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>, Sebastian Andrzej Siewior
	<bigeasy@...utronix.de>
Subject: Re: [patch 06/12] rseq: Implement sys_rseq_slice_yield()

Hello Thomas,

On 9/9/2025 4:30 AM, Thomas Gleixner wrote:
> --- a/kernel/rseq.c
> +++ b/kernel/rseq.c
> @@ -542,6 +542,15 @@ int rseq_slice_extension_prctl(unsigned
>  	return -EFAULT;
>  }
>  

nit.

Perhaps a small note here to highlight how need_resched() is true
for tasks who had the slice extension granted. Something like:

/**
 * sys_rseq_slice_yield - yield the current processor if a task granted with
 * slice extension is done with the critical work before being forced out.
 *
 * This syscall entry work ensures NEED_RESCHED is set if the task was granted
 * a slice extension before arriving here.
 *
 * Return: 1 if the task successfully yielded the CPU within the granted slice.
 *	   0 if the slice extension was either never granted or was revoked by
 *	   going over the granted extension.
 */

> +SYSCALL_DEFINE0(rseq_slice_yield)
> +{
> +	if (need_resched()) {
> +		schedule();
> +		return 1;
> +	}
> +	return 0;
> +}

-- 
Thanks and Regards,
Prateek