[Intel-gfx] [PATCH igt] lib: Avoid actually throttling from igt_require_gem()

[Michał Winiarski]

On Fri, Aug 18, 2017 at 11:53:22AM +0100, Chris Wilson wrote:
> Quoting Chris Wilson (2017-08-18 11:46:19)
> > 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.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> > ---
> >  lib/drmtest.c        | 37 +++++++++++++++++++++++++++++++++++++
> >  lib/ioctl_wrappers.c |  8 ++++++++
> >  2 files changed, 45 insertions(+)
> > 
> > diff --git a/lib/drmtest.c b/lib/drmtest.c
> > index 158af682..0f8bd604 100644
> > --- a/lib/drmtest.c
> > +++ b/lib/drmtest.c
> > @@ -318,6 +318,43 @@ static int __drm_open_driver_render(int chipset)
> >         return fd;
> >  }
> >  
> > +int __drm_reopen_driver(int fd)
> > +{
> > +       struct stat target;
> > +       const char *base;
> > +       int offset;
> > +
> > +       if (fstat(fd, &target))
> > +               return -errno;
> > +
> > +       if (target.st_rdev & 0x80) { /* render node */
> > +               base = "/dev/dri/renderD%d";
> > +               offset = 0x80;
> > +       } else {
> > +               base = "/dev/dri/card%d";
> > +               offset = 0;
> > +       }
> > +
> > +       for (int i = 0; i < 16; i++) {
> > +               struct stat st;
> > +               char buf[256];
> > +
> > +               snprintf(buf, sizeof(buf), base, i + offset);
> > +               fd = open(buf, O_RDWR);
> > +               if (fd < 0)
> > +                       continue;
> > +
> > +               if (fstat(fd, &st) == 0 &&
> > +                   st.st_mode == target.st_mode &&
> > +                   st.st_rdev == target.st_rdev)
> > +                       return fd;
> 
> Or should we try a readlink of /proc/self/fd/$fd?
> -Chris

Seems simpler - we won't need to "duplicate" drm_open_driver.

-Michał