On Tue, Apr 07, 2015 at 03:51:44PM +0200, Maarten Lankhorst wrote:
> Op 07-04-15 om 15:37 schreef Daniel Vetter:
> > On Tue, Apr 07, 2015 at 11:32:02AM +0200, Maarten Lankhorst wrote:
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> >> ---
> >> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> >> index b13c5526a73b..7aaf8eddf19c 100644
> >> --- a/drivers/gpu/drm/i915/i915_drv.h
> >> +++ b/drivers/gpu/drm/i915/i915_drv.h
> >> @@ -2146,14 +2146,14 @@ i915_gem_request_unreference(struct drm_i915_gem_request *req)
> >> static inline void
> >> i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
> >> {
> >> - if (req && !atomic_add_unless(&req->ref.refcount, -1, 1)) {
> >> - struct drm_device *dev = req->ring->dev;
> >> + struct drm_device *dev;
> >> +
> >> + if (!req)
> >> + return;
> >>
> >> - mutex_lock(&dev->struct_mutex);
> >> - if (likely(atomic_dec_and_test(&req->ref.refcount)))
> >> - i915_gem_request_free(&req->ref);
> >> + dev = req->ring->dev;
> >> + if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
> >> mutex_unlock(&dev->struct_mutex);
> > We don't need this conditional unlock here since that's only possible if
> > you have a weak reference somewhere (i.e. using kref_get_unless_zero). If
> > the object only has strong references and you're dropping the last one it
> > can't magically get resurrected somehow.
> Because we use the same put call for kref_put and kref_put_mutex we do need to unlock struct_mutex here,
> kref_put_mutex doesn't release the mutex if true, so either the release call needs to do it or the callee.
Indeed I didn't realize that all existing users of kref_put_mutex unlock
the mutex in the free callback. So looks all good, so applied it.
Thanks, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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