linux-kernel - Re: [PATCH V4 1/6] Sched: Scheduler time slice extension

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Message-ID: <e7e5acae-f372-45f9-aa7d-c4126ea4be1a@efficios.com>
Date: Fri, 23 May 2025 16:06:31 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Prakash Sangappa <prakash.sangappa@...cle.com>,
 linux-kernel@...r.kernel.org
Cc: peterz@...radead.org, rostedt@...dmis.org, tglx@...utronix.de,
 bigeasy@...utronix.de, kprateek.nayak@....com
Subject: Re: [PATCH V4 1/6] Sched: Scheduler time slice extension

On 2025-05-13 17:45, Prakash Sangappa wrote:
[...]
> diff --git a/kernel/rseq.c b/kernel/rseq.c
> index b7a1ec327e81..dba44ca9f624 100644
> --- a/kernel/rseq.c
> +++ b/kernel/rseq.c
> @@ -448,6 +448,62 @@ void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs)
>   	force_sigsegv(sig);
>   }
>   
> +bool rseq_delay_resched(void)
> +{
> +	struct task_struct *t = current;
> +	u32 flags;
> +
> +	if (!IS_ENABLED(CONFIG_SCHED_HRTICK))
> +		return false;
> +
> +	if (!t->rseq)
> +		return false;
> +
> +	if (t->sched_time_delay)
> +		return false;
> +
> +	if (copy_from_user_nofault(&flags, &t->rseq->flags, sizeof(flags)))
> +		return false;

This considers rseq->flags, but not rseq->rseq_cs->flags. Am I missing
something ?

Thanks,

Mathieu

> +
> +	if (!(flags & RSEQ_CS_FLAG_DELAY_RESCHED))
> +		return false;
> +
> +	flags &= ~RSEQ_CS_FLAG_DELAY_RESCHED;
> +	if (copy_to_user_nofault(&t->rseq->flags, &flags, sizeof(flags)))
> +		return false;
> +
> +	t->sched_time_delay = 1;
> +
> +	return true;
> +}
> +


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