[PATCH 0/1] drm/i915/active: Fix misuse of non-idle barriers as fence trackers

[Janusz Krzysztofik]

Test-with: <20230213095040.13457-2-janusz.krzysztofik at linux.intel.com>

Users reported oopses on list corruptions when using i915 perf with a
number of concurrently running graphics applications.  Root cause analysis
pointed out to an issue in barrier processing code -- a race among perf
open / close replacing active barriers with perf requests on kernel
contexts and concurrent barrier preallocate / acquire operations performed
during user context first pin / last unpin.

Respect results of barrier deletion attempts -- mark the barrier as idle
only after successfully deleted from the list.  Then, before proceeding
with setting our fence as the one currently tracked, make sure that the
tracker we've got is not a non-idle barrier.  If that check fails, don't
use that tracker but go back and try to acquire a new, usable one.

Note:
I'm submitting this fix with a request to CI for testing it with a new
subtest igt at gem_barrier_race@remote-request, developed for that case,
not yet in upstream IGT.  I've selected trybot submission of the test,
with the test added to BAT testlist, to get results from the widest
possible HW range.

Janusz Krzysztofik (1):
  drm/i915/active: Fix misuse of non-idle barriers as fence trackers

 drivers/gpu/drm/i915/i915_active.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

-- 
2.25.1