ttm_bo_vm_fault_reserved() invokes dma_fence_get(), which returns a
reference of the specified dma_fence object to "moving" with increased
refcnt.
When ttm_bo_vm_fault_reserved() returns, local variable "moving" becomes
invalid, so the refcount should be decreased to keep refcount balanced.
The reference counting issue happens in several exception handling paths
of ttm_bo_vm_fault_reserved(). When those error scenarios occur such as
"err" equals to -EBUSY, the function forgets to decrease the refcnt
increased by dma_fence_get(), causing a refcnt leak.
Fix this issue by calling dma_fence_put() when no_wait_gpu flag is
equals to true.
Signed-off-by: Xiyu Yang <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index a43aa7275f12..fa03fab02076 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -300,8 +300,10 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
break;
case -EBUSY:
case -ERESTARTSYS:
+ dma_fence_put(moving);
return VM_FAULT_NOPAGE;
default:
+ dma_fence_put(moving);
return VM_FAULT_SIGBUS;
}
--
2.7.4
Am 13.06.20 um 14:28 schrieb Xiyu Yang:
> ttm_bo_vm_fault_reserved() invokes dma_fence_get(), which returns a
> reference of the specified dma_fence object to "moving" with increased
> refcnt.
>
> When ttm_bo_vm_fault_reserved() returns, local variable "moving" becomes
> invalid, so the refcount should be decreased to keep refcount balanced.
>
> The reference counting issue happens in several exception handling paths
> of ttm_bo_vm_fault_reserved(). When those error scenarios occur such as
> "err" equals to -EBUSY, the function forgets to decrease the refcnt
> increased by dma_fence_get(), causing a refcnt leak.
>
> Fix this issue by calling dma_fence_put() when no_wait_gpu flag is
> equals to true.
>
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
Good catch, Reviewed-by: Christian König <[email protected]>.
Going to pick that up for drm-misc-fixes.
Christian.
> ---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index a43aa7275f12..fa03fab02076 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -300,8 +300,10 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> break;
> case -EBUSY:
> case -ERESTARTSYS:
> + dma_fence_put(moving);
> return VM_FAULT_NOPAGE;
> default:
> + dma_fence_put(moving);
> return VM_FAULT_SIGBUS;
> }
>