[Mesa-dev] [PATCH] i965: Solve Android native fence fd double close issue

[Emil Velikov]

On 27 April 2017 at 12:14, Xu, Randy <randy.xu at intel.com> wrote:
> Hi, Chad
>
> Please review this patch, we need it to solve some instability issues
>
The patch is correct, although the commit message can be improved upon.
Read through the following example and consider the alternative
solution mentioned within.

Then either polish and resend, or send patch that implements plan B.
If you opt for B you want to drop the dup/close from the existing
users - freedreno and etnaviv.

"
The semantics of __DRI2fenceExtensionRec::create_fence_fd are unclear
if the DRI driver takes ownership of the fd or not.
Since the i965 driver supports both "in" and "out" fd it assumes "yes,
driver takes ownership", which results in a double close.
First time in our destroy_fence() callback and then in the loader.

Other DRI modules rely on the loader issuing close().

Thus we have two solutions:
 - dup() the file descriptor
 - close() only if we have an out fence.

This patch implements the former, simpler solution.

Fixes: 6403e376511 ("i965/sync: Implement fences based on Linux sync_file")
Reviewed-by: Emil Velikov <emil.velikov at collabora.com>
"

In either case you want to augment create_fence_fd and destroy_fence
(in dri_interface.h) to explicitly define the behaviour.
Please keep that a separate patch part of this series.

Thanks
Emil