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Date: Thu, 2 Mar 2017 11:52:25 +0900
From: Byungchul Park <byungchul.park@lge.com>
To: Peter Zijlstra <peterz@infradead.org>
CC: <mingo@kernel.org>, <tglx@linutronix.de>, <walken@google.com>,
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Subject: Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature
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On Wed, Mar 01, 2017 at 02:17:07PM +0900, Byungchul Park wrote:
> > > +void lock_commit_crosslock(struct lockdep_map *lock)
> > > +{
> > > +	struct cross_lock *xlock;
> > > +	unsigned long flags;
> > > +
> > > +	if (!current->xhlocks)
> > > +		return;
> > > +
> > > +	if (unlikely(current->lockdep_recursion))
> > > +		return;
> > > +
> > > +	raw_local_irq_save(flags);
> > > +	check_flags(flags);
> > > +	current->lockdep_recursion = 1;
> > > +
> > > +	if (unlikely(!debug_locks))
> > > +		return;
> > > +
> > > +	if (!graph_lock())
> > > +		return;
> > > +
> > > +	xlock = &((struct lockdep_map_cross *)lock)->xlock;
> > > +	if (atomic_read(&xlock->ref) > 0 && !commit_xhlocks(xlock))
> > 
> > You terminate with graph_lock() held.
> 
> Oops. What did I do? I'll fix it.

I remembered it. It's no problem because it would terminate there, only
if _both_ 'xlock->ref > 0' and 'commit_xhlocks returns 0' are true.
Otherwise, it will unlock the lock safely.