linux-kernel - Re: Linux 6.3-rc2

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Message-ID: <CAMj1kXHC+UCaWLRrujEJeqVaQ_4Wn3dQ+Mq+1ryQj6C=Qsb53w@mail.gmail.com>
Date:   Tue, 14 Mar 2023 13:01:27 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 6.3-rc2

On Tue, 14 Mar 2023 at 12:40, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Mar 14, 2023 at 12:18:33PM +0100, Frederic Weisbecker wrote:
> > How does the following look like as a culprit?
> >
> > 62b95a7b44d1 (ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled)
>
> Ooh yeah, that asm implementation of local_bh_{dis,en}able completely
> miss out on the lockdep state tracking. Also I think it breaks RCU, note
> how __local_bh_disable_ip() explicitly does rcu_read_lock() for the
> first bh-disable.
>

Thanks a lot for the diagnosis, doctor :-)

I may need some hand holding getting this fixed - probably better to
run the C implementations wherever feasible, right?