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

[Pierre Moreau]

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.

Best regards,
Pierre

[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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