Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260

Peter Zijlstra
2016-03-30T10:36:07Z

On Wed, Mar 30, 2016 at 05:59:54PM +0800, Boqun Feng wrote:
> > @@ -3164,6 +3181,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
> > hlock->acquire_ip = ip;
> > hlock->instance = lock;
> > hlock->nest_lock = nest_lock;
> > + hlock->irq_context = 2*(!!curr->hardirq_context) + !!curr->softirq_context;
> > hlock->trylock = trylock;
> > hlock->read = read;
> > hlock->check = check;
>
> This is just for cleaning up, right? However ->hardirq_context and
> ->softirq_context only defined when CONFIG_TRACE_IRQFLAGS=y.

Ah, that is the reason it was in a 'funny' place.

The other reason is that we're careful to reduce hardirq_context to 0,1
but don't do so for softirq_context.

> So we should use macro like current_hardirq_context() here? Or
> considering the two helpers introduced in my RFC:
>
> http://lkml.kernel.org/g/1455602265-16490-2-git-send-email-boqun.feng@gmail.com
>
> if you don't think that overkills ;-)

Yeah, that might work, although I would like to keep the !! on both,
makes me worry less.