[Linaro-mm-sig] [PATCH] dma-buf: add some lockdep asserts to the reservation object implementation

[Lucas Stach]

Am Donnerstag, den 11.01.2018, 11:54 +0100 schrieb Christian König:
> Yeah, somehow missed that one.
> 
> The patch looks mostly good, except for reservation_object_get_excl().
> 
> For that one an RCU protection is usually sufficient, so annotating it 
> with reservation_object_assert_held() sounds incorrect to me.

Ah, you are correct. I was confused about this one as
reservation_object_get_excl_rcu() exists and and the doc
above reservation_object_get_excl() states "The obj->lock must be
held.", which is misleading for the read-only case.

I'll send a v2 with that fixed.

Regards,
Lucas

> Regards,
> Christian.
> 
> Am 11.01.2018 um 11:43 schrieb Lucas Stach:
> > Did this fall through the cracks over the holidays? It really has made
> > my work much easier while reworking some of the reservation object
> > handling in etnaviv and I think it might benefit others.
> > 
> > Regards,
> > Lucas
> > 
> > Am Freitag, den 01.12.2017, 12:12 +0100 schrieb Lucas Stach:
> > > This adds lockdep asserts to the reservation functions which state in their
> > > documentation that obj->lock must be held. Allows builds with PROVE_LOCKING
> > > enabled to check that the locking requirements are met.
> > > 
> > > > Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
> > > 
> > > ---
> > >   drivers/dma-buf/reservation.c | 8 ++++++++
> > >   include/linux/reservation.h   | 2 ++
> > >   2 files changed, 10 insertions(+)
> > > 
> > > diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> > > index b44d9d7db347..accd398e2ea6 100644
> > > --- a/drivers/dma-buf/reservation.c
> > > +++ b/drivers/dma-buf/reservation.c
> > > @@ -71,6 +71,8 @@ int reservation_object_reserve_shared(struct reservation_object *obj)
> > > > > > > >   	struct reservation_object_list *fobj, *old;
> > > >   	u32 max;
> > > 
> > >   
> > > > +	reservation_object_assert_held(obj);
> > > 
> > > +
> > > >   	old = reservation_object_get_list(obj);
> > > 
> > >   
> > > >   	if (old && old->shared_max) {
> > > 
> > > @@ -211,6 +213,8 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
> > >   {
> > > >   	struct reservation_object_list *old, *fobj = obj->staged;
> > > 
> > >   
> > > > +	reservation_object_assert_held(obj);
> > > 
> > > +
> > > > > > > >   	old = reservation_object_get_list(obj);
> > > >   	obj->staged = NULL;
> > > 
> > >   
> > > @@ -236,6 +240,8 @@ void reservation_object_add_excl_fence(struct reservation_object *obj,
> > > > > > > >   	struct reservation_object_list *old;
> > > >   	u32 i = 0;
> > > 
> > >   
> > > > +	reservation_object_assert_held(obj);
> > > 
> > > +
> > > > > > > >   	old = reservation_object_get_list(obj);
> > > > > > > >   	if (old)
> > > >   		i = old->shared_count;
> > > 
> > > @@ -276,6 +282,8 @@ int reservation_object_copy_fences(struct reservation_object *dst,
> > > > > > > >   	size_t size;
> > > >   	unsigned i;
> > > 
> > >   
> > > > +	reservation_object_assert_held(dst);
> > > 
> > > +
> > > > > > > >   	rcu_read_lock();
> > > >   	src_list = rcu_dereference(src->fence);
> > > 
> > >   
> > > diff --git a/include/linux/reservation.h b/include/linux/reservation.h
> > > index 21fc84d82d41..55e7318800fd 100644
> > > --- a/include/linux/reservation.h
> > > +++ b/include/linux/reservation.h
> > > @@ -212,6 +212,8 @@ reservation_object_unlock(struct reservation_object *obj)
> > >   static inline struct dma_fence *
> > >   reservation_object_get_excl(struct reservation_object *obj)
> > >   {
> > > > +	reservation_object_assert_held(obj);
> > > 
> > > +
> > > > > > > >   	return rcu_dereference_protected(obj->fence_excl,
> > > >   					 reservation_object_held(obj));
> > > 
> > >   }
> > 
> > _______________________________________________
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> 
>