Re: [PATCH v3 30/30] locking/lockdep: Remove irq-safe to irq-unsafe read check

Yuyang Du
2019-07-10T06:30:21Z

Thanks for review.

On Wed, 10 Jul 2019 at 13:30, Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Fri, Jun 28, 2019 at 05:15:28PM +0800, Yuyang Du wrote:
> > We have a lockdep warning:
> >
> > ========================================================
> > WARNING: possible irq lock inversion dependency detected
> > 5.1.0-rc7+ #141 Not tainted
> > --------------------------------------------------------
> > kworker/8:2/328 just changed the state of lock:
> > 0000000007f1a95b (&(&host->lock)->rlock){-...}, at: ata_bmdma_interrupt+0x27/0x1c0 [libata]
> > but this lock took another, HARDIRQ-READ-unsafe lock in the past:
> > (&trig->leddev_list_lock){.+.?}
> >
> > and interrupts could create inverse lock ordering between them.
> >
> > other info that might help us debug this:
> > Possible interrupt unsafe locking scenario:
> >
> > CPU0 CPU1
> > ---- ----
> > lock(&trig->leddev_list_lock);
> > local_irq_disable();
> > lock(&(&host->lock)->rlock);
> > lock(&trig->leddev_list_lock);
> > <Interrupt>
> > lock(&(&host->lock)->rlock);
> >
> > *** DEADLOCK ***
> >
> > This splat is a false positive, which is enabled by the addition of
>
> If so, I think the better way is to reorder this patch before recursive
> read lock suppport, for better bisect-ability.

Good suggestion.

Thanks,
Yuyang