[PATCH v3 2/6] dma-buf: set signaling bit for the stub fence

[Arvind Yadav <Arvind.Yadav@amd.com>]

Here's setting software signaling bit for the stub fence
which is always signaled. If this fence signaling bit is
not set then the AMD GPU scheduler will cause a GPU reset
due to a GPU scheduler cleanup activity timeout.

Signed-off-by: Arvind Yadav <Arvind.Yadav@amd.com>
---

Changes in v1 :
1- Addressing Christian's comment to remove unnecessary callback.
2- Replacing CONFIG_DEBUG_WW_MUTEX_SLOWPATH instead of CONFIG_DEBUG_FS.
3- The version of this patch is also changed and previously
it was [PATCH 3/4]

Changes in v2 : 
1 - perviously using  __dma_fence_enable_signaling() for enable
signaling.
2 - #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH  removed

---
 drivers/dma-buf/dma-fence.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 64c99739ad23..bead1a6e9f59 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -136,6 +136,10 @@ struct dma_fence *dma_fence_get_stub(void)
 			       &dma_fence_stub_ops,
 			       &dma_fence_stub_lock,
 			       0, 0);
+
+		set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
+			&dma_fence_stub.flags);
+
 		dma_fence_signal_locked(&dma_fence_stub);
 	}
 	spin_unlock(&dma_fence_stub_lock);
-- 
2.25.1