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

Ard Biesheuvel ard.biesheuvel at linaro.org
Fri Dec 8 18:30:34 UTC 2017

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

    if (!refcount_inc_not_zero(&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;
 			iobj->base.memory.ptrs = &nv50_instobj_slow;
-		refcount_inc(&iobj->maps);
+		refcount_set(&iobj->maps, 1);

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