linux-kernel - Re: [PATCH -v2] seqlock, procfs: Match scoped_seqlock_read() critical section vs. RCU ordering in do_task_stat() to do_io

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Message-ID: <aS689gFv5gi1qTwF@gmail.com>
Date: Tue, 2 Dec 2025 11:18:30 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -v2] seqlock, procfs: Match scoped_seqlock_read()
 critical section vs. RCU ordering in do_task_stat() to do_io_accounting()

* Oleg Nesterov <oleg@...hat.com> wrote:

> On 12/02, Ingo Molnar wrote:
> >
> > * Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > > 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...
> >
> > Yeah, true - it's allowed and not a bug,
> 
> OK, thanks ;)
> 
> > merely
> > discouraged inside irqs-off sections if it can be
> > avoided, and it's an inconsistency versus
> > do_io_accounting().
> 
> Yes, yes, agreed
> 
> > How about the -v2 phrasing below? I also removed the
> > Fixes tags.
> 
> Acked-by: Oleg Nesterov <oleg@...hat.com>

Thanks Oleg!

	Ingo