[PATCH] drm/amdgpu: don't try to unreserve NULL pointer

[Zhu, Rex]

> -----Original Message-----
> From: Christian König <ckoenig.leichtzumerken at gmail.com>
> Sent: Tuesday, September 18, 2018 3:14 PM
> To: Zhu, Rex <Rex.Zhu at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: don't try to unreserve NULL pointer
> 
> Am 18.09.2018 um 08:16 schrieb Zhu, Rex:
> >
> >> -----Original Message-----
> >> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
> >> Christian König
> >> Sent: Tuesday, September 18, 2018 2:07 AM
> >> To: amd-gfx at lists.freedesktop.org
> >> Subject: [PATCH] drm/amdgpu: don't try to unreserve NULL pointer
> >>
> >> Don't try to unreserve a BO we doesn't allocated.
> >>
> >> Fixes: 07012fdd497e drm/amdgpu: don't allocate zero sized kernel BOs
> >>
> >> Signed-off-by: Christian König <christian.koenig at amd.com>
> >> ---
> >>   drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 3 ++-
> >>   1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> >> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> >> index 84d82d5382f9..c1387efc0c91 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> >> @@ -348,7 +348,8 @@ int amdgpu_bo_create_kernel(struct
> amdgpu_device
> >> *adev,
> >>	if (r)
> >>   		return r;
> >> -	amdgpu_bo_unreserve(*bo_ptr);
> >> +	if (*bo_ptr)
> >> +		amdgpu_bo_unreserve(*bo_ptr);
> >>
> >>   	return 0;
> >>   }
> > It is weird.
> > If we return true for allocate bo with size  0.
> > Does that mean we need to check all the bo_ptr before we use them.
> 
> No, allocating a BO with zero size doesn't make much sense and was
> essentially undefined behavior previously.
> 
> So now we get a defined behavior, but not necessary the one you expected.
> 
> Is that only a rhetorical question or really a problem somewhere?

Logically, the code is trick. It also make the  code
if (r)
	return r; 
redundant.

Regards
Rex

> Regards,
> Christian.
> 
> >
> > Best Regards
> > Rex
> >
> >> --
> >> 2.14.1
> >>
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