[Mesa-dev] [PATCH] clover: Handle NULL pipe_loader_device returned by pipe_loader_probe()

[Francisco Jerez]

Tom Stellard <thomas.stellard at amd.com> writes:

> pipe_loader_probe() may initalize an entry in the device list to NULL,
> while still counting this device in the number of devices that it
> returns, so we need to handle this situation.

If this is related to the patch you sent last Saturday
(1448679128-20276-1-git-send-email-thomas.stellard at amd.com), I don't
think that's what happens.  What happens is that pipe_loader_sw_probe()
returns an incorrect device count the first time around (one regardless
of whether the software null device is actually available), so Clover
allocates and zero-initializes a pointer in the ldevs array for a device
which is never returned by pipe-loader, and then crashes.

Please mention in the commit message that this is actually working
around a pipe-loader bug, but it makes sense to do it anyway because it
fixes the theoretical race condition you pointed out in your last patch.

> ---
>
> This is the most simple fix possible to get clover working again.  We can
> discuss fixing the other issues in clover in a follow on patch.
>
> src/gallium/state_trackers/clover/core/platform.cpp | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/src/gallium/state_trackers/clover/core/platform.cpp b/src/gallium/state_trackers/clover/core/platform.cpp
> index 328b71c..871b90e 100644
> --- a/src/gallium/state_trackers/clover/core/platform.cpp
> +++ b/src/gallium/state_trackers/clover/core/platform.cpp
> @@ -31,6 +31,9 @@ platform::platform() : adaptor_range(evals(), devs) {
>     pipe_loader_probe(&ldevs.front(), n);
>  
>     for (pipe_loader_device *ldev : ldevs) {
> +      if (!ldev) {
> +         continue;
> +      }
>        try {

Just nitpicking now, but I'd prefer to simplify this even more by doing
the following here:

+        if (ldev)

>           devs.push_back(create<device>(*this, ldev));
>        } catch (error &) {
> -- 
> 2.0.4
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