[PATCH] dma-buf/sync_file: Increment refcount of fence when all are signaled.

[Chris Wilson]

On Wed, Sep 14, 2016 at 04:46:18PM -0700, Rafael Antognolli wrote:
> When we merge several fences, if all of them are signaled already, we
> still keep one of them. So instead of using add_fence(), which will not
> increase the refcount of signaled fences, we should explicitly call
> fence_get() for the fence we are keeping.
> 
> This patch fixes a kernel panic that can be triggered by creating a fence that
> is expired (or increasing the timeline until it expires), then creating a
> merged fence out of it, and deleting the merged fence. This will make the
> original expired fence's refcount go to zero.
> 

Testcase: igt/sw_sync/...?
> Signed-off-by: Rafael Antognolli <rafael.antognolli at intel.com>

Lgtm,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre