[Nouveau] [PATCH] drm/nouveau/imem/nv50: fix incorrect use of refcount API

[Ard Biesheuvel]

On 18 December 2017 at 13:16, Pierre Moreau <pierre.morrow at free.fr> wrote:
> Hey Ard,
>
> It seems that Ben already committed a similar patch to his tree (see [0]). I do
> not know whether he is planning to have it part of a pull request of fixes for
> 4.15.
>

Hi Pierre,

Thanks for the reply. If a fix has been queued, I don't mind leaving
it up to Ben to decide when it gets sent onwards.

-- 
Ard.

> [0]: https://github.com/skeggsb/nouveau/commit/9068f1df2394f0e4ab2b2a28cac06b462fe0a0aa
>
> On 2017-12-18 — 09:27, Ard Biesheuvel wrote:
>> On 8 December 2017 at 19:30, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
>> > Commit be55287aa5b ("drm/nouveau/imem/nv50: embed nvkm_instobj directly
>> > into nv04_instobj") introduced some new calls to the refcount api to
>> > the nv50 mapping code. In one particular instance, it does the
>> > following:
>> >
>> >     if (!refcount_inc_not_zero(&iobj->maps)) {
>> >             ...
>> >             refcount_inc(&iobj->maps);
>> >     }
>> >
>> > i.e., it calls refcount_inc() to increment the refcount when it is known
>> > to be zero, which is explicitly forbidden by the API. Instead, use
>> > refcount_set() to set it to 1.
>> >
>> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> > ---
>> >
>> > Apologies if this was already found and fixed. I don't usually follow
>> > the DRM or nouveau mailing lists.
>> >
>> >  drivers/gpu/drm/nouveau/nvkm/subdev/instmem/nv50.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/nv50.c b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/nv50.c
>> > index 1ba7289684aa..db48a1daca0c 100644
>> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/nv50.c
>> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/nv50.c
>> > @@ -249,7 +249,7 @@ nv50_instobj_acquire(struct nvkm_memory *memory)
>> >                         iobj->base.memory.ptrs = &nv50_instobj_fast;
>> >                 else
>> >                         iobj->base.memory.ptrs = &nv50_instobj_slow;
>> > -               refcount_inc(&iobj->maps);
>> > +               refcount_set(&iobj->maps, 1);
>> >         }
>> >
>> >         mutex_unlock(&imem->subdev.mutex);
>> > --
>> > 2.11.0
>> >
>>
>> Ping?
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