Re: [PATCH 1/2] dma-buf: keep only not signaled fence in reservation_object_add_shared_replace v2

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 31.10.2017 um 09:51 schrieb Chunming Zhou:
> On 2017年10月31日 16:43, Christian König wrote:
> > The amdgpu issue to also need signaled fences in the reservation objects
> > should be fixed by now.
> >
> > Optimize the list by keeping only the not signaled yet fences around.
> >
> > v2: temporary put the signaled fences at the end of the new container
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   drivers/dma-buf/reservation.c | 36 
> > ++++++++++++++++++++++++++----------
> >   1 file changed, 26 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/dma-buf/reservation.c 
> > b/drivers/dma-buf/reservation.c
> > index b44d9d7db347..6fc794576997 100644
> > --- a/drivers/dma-buf/reservation.c
> > +++ b/drivers/dma-buf/reservation.c
> > @@ -145,8 +145,8 @@ reservation_object_add_shared_replace(struct 
> > reservation_object *obj,
> >                         struct reservation_object_list *fobj,
> >                         struct dma_fence *fence)
> >   {
> > -    unsigned i;
> >       struct dma_fence *old_fence = NULL;
> > +    unsigned i, j, k;
> >         dma_fence_get(fence);
> >   @@ -162,9 +162,7 @@ reservation_object_add_shared_replace(struct 
> > reservation_object *obj,
> >        * references from the old struct are carried over to
> >        * the new.
> >        */
> > -    fobj->shared_count = old->shared_count;
> > -
> > -    for (i = 0; i < old->shared_count; ++i) {
> > +    for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; 
> > ++i) {
> >           struct dma_fence *check;
> >             check = rcu_dereference_protected(old->shared[i],
> > @@ -172,10 +170,18 @@ reservation_object_add_shared_replace(struct 
> > reservation_object *obj,
> >             if (!old_fence && check->context == fence->context) {
> >               old_fence = check;
> > -            RCU_INIT_POINTER(fobj->shared[i], fence);
> > -        } else
> > -            RCU_INIT_POINTER(fobj->shared[i], check);
> > +            RCU_INIT_POINTER(fobj->shared[j++], fence);
> > +        } else if (!dma_fence_is_signaled(check)) {
> > +            RCU_INIT_POINTER(fobj->shared[j++], check);
> > +        } else {
> > +            /*
> > +             * Temporary save the signaled fences at the end of the
> > +             * new container
> > +             */
> > +            RCU_INIT_POINTER(fobj->shared[--k], check);
> > +        }
> >       }
> > +    fobj->shared_count = j;
> >       if (!old_fence) {
> > RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
> Seems you still don't address here, how do you sure 
> fobj->shared[fobj->shared_count] is null? if not NULL, the old one 
> will be leak.

I've put them at the end of the container, see above "k = 
fobj->shared_max". Since shared_max >> shared_count (at least twice as 
large in this situation) we should be on the save side.

Regards,
Christian.

> Regards,
> David Zhou
> >           fobj->shared_count++;
> > @@ -192,10 +198,20 @@ reservation_object_add_shared_replace(struct 
> > reservation_object *obj,
> >       write_seqcount_end(&obj->seq);
> >       preempt_enable();
> >   -    if (old)
> > -        kfree_rcu(old, rcu);
> > -
> >       dma_fence_put(old_fence);
> > +
> > +    if (!old)
> > +        return;
> > +
> > +    /* Drop the references to the signaled fences */
> > +    for (i = k; i < fobj->shared_max; ++i) {
> > +        struct dma_fence *f;
> > +
> > +        f = rcu_dereference_protected(fobj->shared[i],
> > +                          reservation_object_held(obj));
> > +        dma_fence_put(f);
> > +    }
> > +    kfree_rcu(old, rcu);
> >   }
> >     /**

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