linux-kernel - Re: [PATCH] seqlock, procfs: Fix scoped_seqlock_read() critical section in do_task

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Message-ID: <aS6VX56DuPWY3bXk@redhat.com>
Date: Tue, 2 Dec 2025 08:29:35 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] seqlock, procfs: Fix scoped_seqlock_read() critical
 section in do_task_stat()

On 12/02, Ingo Molnar wrote:
>
> RCU read-lock should not nest inside a read-seqlock
> irqsave ->stats_lock IRQs-off critical section,

Hmm... I agree with this patch, but is it actually wrong?

I thought that rcu_read_lock/unlock is safe under spin_lock_irq...

> +	{
> +		guard(rcu)();
> +		scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) {

how about

	scoped_guard(rcu)  {
		scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) {
			...
		}
	}
		
?

Oleg.