drm/radeon: hold reference to fences in radeon_sa_bo_new (3.17 and older)

[Backport of upstream commit f6ff4f67cdf8455d0a4226eeeaf5af17c37d05eb, with
 an additional NULL pointer guard that is required for kernels 3.17 and older.

 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/gpu/drm/radeon/radeon_sa.c b/drivers/gpu/drm/radeon/radeon_sa.c
index f0bac68254b79a5dd31cfdc14ce80a98bca91065..8962411b5f2b7afa8058a65ca456132b2763dfe5 100644 (file)
--- 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 && block) {