On Tue, Feb 18, 2020 at 08:48:21PM -0800, Darrick J. Wong wrote:
> > > +static inline bool
> > > +__xfs_rwsem_islocked(
> > > + struct rw_semaphore *rwsem,
> > > + bool shared,
> > > + bool excl)
> > > +{
> > > + bool locked = false;
> > > +
> > > + if (!rwsem_is_locked(rwsem))
> > > + return false;
> > > +
> > > + if (!debug_locks)
> > > + return true;
> > > +
> > > + if (shared)
> > > + locked = lockdep_is_held_type(rwsem, 0);
> > > +
> > > + if (excl)
> > > + locked |= lockdep_is_held_type(rwsem, 1);
> > > +
> > > + return locked;
> >
> > This could use some comments explaining the logic, especially why we
> > need the shared and excl flags, which seems very confusing given that
> > a lock can be held either shared or exclusive, but not neither and not
> > both.
>
> Yes, this predicate should document that callers are allowed to pass in
> shared==true and excl==true when the caller wants to assert that either
> lock type (shared or excl) of a given lock class (e.g. iolock) are held.
Looking at the lockdep_is_held_type implementation, and our existing
code for i_rwsem I really don't see the point of the extra shared
check. Something like:
static inline bool
__xfs_rwsem_islocked(
struct rw_semaphore *rwsem,
bool excl)
{
if (rwsem_is_locked(rwsem)) {
if (debug_locks && excl)
return lockdep_is_held_type(rwsem, 1);
return true;
}
return false;
}
should be all that we really need.
