Re: [PATCH] drm/radeon: hold reference to fences in radeon_sa_bo_new (3.17 and older)

[Luis Henriques <luis.henriques@canonical.com>]

On Tue, Mar 15, 2016 at 12:56:45PM -0500, Nicolai Hähnle wrote:
> From: Nicolai Hähnle <nicolai.haehnle@amd.com>
> 
> [Backport of upstream commit f6ff4f67cdf8455d0a4226eeeaf5af17c37d05eb, with
>  an additional NULL pointer guard that is required for kernels 3.17 and older.
>

Thank you, Nicolai.  I'll queue this backport for the 3.16.

Cheers,
--
Luís


>  To be precise, any kernel that does *not* have commit 954605ca3 "drm/radeon:
>  use common fence implementation for fences, v4" requires this additional
>  NULL pointer guard.]
> 
> An arbitrary amount of time can pass between spin_unlock and
> radeon_fence_wait_any, so we need to ensure that nobody frees the
> fences from under us.
> 
> Based on the analogous fix for amdgpu.
> 
> Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
> Reviewed-by: Christian König <christian.koenig@amd.com> (v1 + fix)
> Tested-by: Lutz Euler <lutz.euler@freenet.de>
> Cc: stable@vger.kernel.org
> ---
>  drivers/gpu/drm/radeon/radeon_sa.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_sa.c b/drivers/gpu/drm/radeon/radeon_sa.c
> index c507896..7d11901 100644
> --- a/drivers/gpu/drm/radeon/radeon_sa.c
> +++ b/drivers/gpu/drm/radeon/radeon_sa.c
> @@ -349,8 +349,15 @@ int radeon_sa_bo_new(struct radeon_device *rdev,
>  			/* see if we can skip over some allocations */
>  		} while (radeon_sa_bo_next_hole(sa_manager, fences, tries));
>  
> +		for (i = 0; i < RADEON_NUM_RINGS; ++i) {
> +			if (fences[i])
> +				radeon_fence_ref(fences[i]);
> +		}
> +
>  		spin_unlock(&sa_manager->wq.lock);
>  		r = radeon_fence_wait_any(rdev, fences, false);
> +		for (i = 0; i < RADEON_NUM_RINGS; ++i)
> +			radeon_fence_unref(&fences[i]);
>  		spin_lock(&sa_manager->wq.lock);
>  		/* if we have nothing to wait for block */
>  		if (r == -ENOENT) {
> -- 
> 2.5.0
> 
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