Date:   Tue, 14 Mar 2023 13:27:25 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     Frederic Weisbecker <frederic@kernel.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 6.3-rc2
Message-ID: <20230314122725.GI1845660@hirez.programming.kicks-ass.net>
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On Tue, Mar 14, 2023 at 01:01:27PM +0100, Ard Biesheuvel wrote:
> On Tue, 14 Mar 2023 at 12:40, Peter Zijlstra <peterz@infradead.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?

That is certainly the easiest and least risky approach yes.