Re: [PATCH igt v2] lib: Avoid actually throttling from igt_require_gem()

["Fiedorowicz, Lukasz" <lukasz.fiedorowicz@intel.com>]

On Thu, 2017-08-24 at 13:42 +0100, Chris Wilson wrote:
> igt_require_gem() checks whether we can use the i915 fd for
> submitting
> requests by detecting a wedged driver. It was intended to be used
> just
> after opening DRIVER_INTEL for a gem test to provide an early skip if
> the device was unusable. However, it is also used at the start of
> library functions like igt_spin_batch_new() which may be called after
> the test has setup some state, and importantly submitted some
> batches.
> igt_require_gem() has the risk of then waiting on those batches,
> unless
> we tell it to use a clean fd.
> 
> v2: Chase the /proc/self/fd/$fd link
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Michał Winiarski <michal.winiarski@intel.com>
> ---
>  lib/ioctl_wrappers.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/lib/ioctl_wrappers.c b/lib/ioctl_wrappers.c
> index 51000bac..d91f29c8 100644
> --- a/lib/ioctl_wrappers.c
> +++ b/lib/ioctl_wrappers.c
> @@ -1598,13 +1598,23 @@ void gem_require_caching(int fd)
>  
>  void igt_require_gem(int fd)
>  {
> +	char path[256];
>  	int err;
>  
>  	igt_require_intel(fd);
>  
> +	/* We only want to use the throttle-ioctl for its -EIO
> reporting
> +	 * of a wedged device, not for actually waiting on
> outstanding
> +	 * requests! So create a new drm_file for the device that is
> clean.
> +	 */
> +	snprintf(path, sizeof(path), "/proc/self/fd/%d", fd);
> +	fd = open(path, O_RDWR);
> +	igt_assert_lte(0, fd);
> +
>  	err = 0;
>  	if (ioctl(fd, DRM_IOCTL_I915_GEM_THROTTLE))
>  		err = -errno;
> +	close(fd);
>  
>  	igt_require_f(err == 0, "Unresponsive i915/GEM device\n");
>  }

I would use PATH_MAX but other than this:
Reviewed-by: Lukasz Fiedorowicz <lukasz.fiedorowicz@intel.com>
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