linux-kernel - Re: [patch V2 05/12] rseq: Add prctl() to enable time slice extensions

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Message-ID: <20251027094019.foWBPFO2@linutronix.de>
Date: Mon, 27 Oct 2025 10:40:19 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	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>, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org
Subject: Re: [patch V2 05/12] rseq: Add prctl() to enable time slice
 extensions

On 2025-10-22 14:57:34 [+0200], Thomas Gleixner wrote:
> --- a/include/linux/rseq.h
> +++ b/include/linux/rseq.h
> @@ -164,4 +164,13 @@ void rseq_syscall(struct pt_regs *regs);
>  static inline void rseq_syscall(struct pt_regs *regs) { }
>  #endif /* !CONFIG_DEBUG_RSEQ */
>  
> +#ifdef CONFIG_RSEQ_SLICE_EXTENSION
> +int rseq_slice_extension_prctl(unsigned long arg2, unsigned long arg3);
> +#else /* CONFIG_RSEQ_SLICE_EXTENSION */
> +static inline int rseq_slice_extension_prctl(unsigned long arg2, unsigned long arg3)
> +{
> +	return -EINVAL;

This should be -ENOTSUPP as in the !rseq_slice_extension_enabled() case.
After all it is the same condition.

> +}

Sebastian