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drm/nouveau/pm: fix a potential race condition when creating an engine context 

There is always the possiblity that the ppm->context pointer would get
partially updated and accidentally would equal ctx. This would allow two
contexts to co-exist, which is not acceptable. Moving the test to the
critical section takes care of this problem.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Signed-off-by: Martin Peres <martin.peres@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Samuel Pitoiset 2015-06-07 22:40:12 +02:00 committed by Ben Skeggs
parent 3693d54405
commit 305c1959ea
1 changed files with 3 additions and 4 deletions
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7
drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
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@ -358,12 +358,11 @@ nvkm_perfctx_ctor(struct nvkm_object *parent, struct nvkm_object *engine,
mutex_lock(&nv_subdev(ppm)->mutex);
if (ppm->context == NULL)
ppm->context = ctx;
if (ctx != ppm->context)
ret = -EBUSY;
mutex_unlock(&nv_subdev(ppm)->mutex);
if (ctx != ppm->context)
return -EBUSY;
return 0;
return ret;
}
struct nvkm_oclass