Re: [PATCH v3 2/2] locking/percpu-rwsem: Annotate rwsem ownership transfer by setting RWSEM_OWNER_UNKNOWN

[Peter Zijlstra]

On Tue, May 15, 2018 at 11:02:19AM -0700, Matthew Wilcox wrote:
> On Tue, May 15, 2018 at 07:58:05PM +0200, Peter Zijlstra wrote:
> > On Tue, May 15, 2018 at 01:38:04PM -0400, Waiman Long wrote:
> > > +/*
> > > + * Owner value to indicate the rwsem's owner is not currently known.
> > > + */
> > > +#define RWSEM_OWNER_UNKNOWN	((struct task_struct *)-1)
> > 
> > It might be nice to comment that this works and relies on having that
> > ANON_OWNER bit set.
> 
> I'd rather change the definition to be ((struct task_struct *)2)
> otherwise this is both reader-owned and anonymously-owned which doesn't
> make much sense.

Works for me.