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drm/amdgpu/userq: Fix fence reference leak on queue teardown v2

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The user mode queue keeps a pointer to the most recent fence in
userq->last_fence. This pointer holds an extra dma_fence reference.

When the queue is destroyed, we free the fence driver and its xarray,
but we forgot to drop the last_fence reference.

Because of the missing dma_fence_put(), the last fence object can stay
alive when the driver unloads. This leaves an allocated object in the
amdgpu_userq_fence slab cache and triggers

This is visible during driver unload as:

  BUG amdgpu_userq_fence: Objects remaining on __kmem_cache_shutdown()
  kmem_cache_destroy amdgpu_userq_fence: Slab cache still has objects
  Call Trace:
    kmem_cache_destroy
    amdgpu_userq_fence_slab_fini
    amdgpu_exit
    __do_sys_delete_module

Fix this by putting userq->last_fence and clearing the pointer during
amdgpu_userq_fence_driver_free().

This makes sure the fence reference is released and the slab cache is
empty when the module exits.

v2: Update to only release userq->last_fence with dma_fence_put()
    (Christian)

Fixes: edc762a51c ("drm/amdgpu/userq: move some code around")
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Srinivasan Shanmugam
2026-01-14 16:14:53 +05:30
committed by Alex Deucher
parent 3fd20580b9
commit 8e051e38a8
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
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@@ -141,6 +141,8 @@ static void amdgpu_userq_walk_and_drop_fence_drv(struct xarray *xa)
void
amdgpu_userq_fence_driver_free(struct amdgpu_usermode_queue *userq)
{
dma_fence_put(userq->last_fence);
amdgpu_userq_walk_and_drop_fence_drv(&userq->fence_drv_xa);
xa_destroy(&userq->fence_drv_xa);
/* Drop the fence_drv reference held by user queue */