[PATCH AUTOSEL 6.6 19/23] drm/amdgpu: grab an additional reference on the gang fence v2

[Sasha Levin]

From: Christian König <christian.koe...@amd.com>

[ Upstream commit 0d9a95099dcb05b5f4719c830d15bf4fdcad0dc2 ]

We keep the gang submission fence around in adev, make sure that it
stays alive.

v2: fix memory leak on retry

Signed-off-by: Christian König <christian.koe...@amd.com>
Acked-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 45dd6cbad81e7..10f5a3d0f5916 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -6015,6 +6015,7 @@ struct dma_fence *amdgpu_device_switch_gang(struct 
amdgpu_device *adev,
 {
        struct dma_fence *old = NULL;
 
+       dma_fence_get(gang);
        do {
                dma_fence_put(old);
                rcu_read_lock();
@@ -6024,12 +6025,19 @@ struct dma_fence *amdgpu_device_switch_gang(struct 
amdgpu_device *adev,
                if (old == gang)
                        break;
 
-               if (!dma_fence_is_signaled(old))
+               if (!dma_fence_is_signaled(old)) {
+                       dma_fence_put(gang);
                        return old;
+               }
 
        } while (cmpxchg((struct dma_fence __force **)&adev->gang_submit,
                         old, gang) != old);
 
+       /*
+        * Drop it once for the exchanged reference in adev and once for the
+        * thread local reference acquired in amdgpu_device_get_gang().
+        */
+       dma_fence_put(old);
        dma_fence_put(old);
        return NULL;
 }
-- 
2.39.5