drm/i915: Lock out execlist tasklet while peeking inside for busy-stats
authorChris Wilson <chris@chris-wilson.co.uk>
Tue, 13 Feb 2018 09:57:44 +0000 (09:57 +0000)
committerRodrigo Vivi <rodrigo.vivi@intel.com>
Wed, 14 Feb 2018 00:55:55 +0000 (16:55 -0800)
commitedb76b01ac1629bfe17158bea56fcc16bfb57854
tree62d149e960539e0b3df202aca2a19a17a6b68573
parent117172c8f9d40ba1de8cb35c6e614422faa03330
drm/i915: Lock out execlist tasklet while peeking inside for busy-stats

In order to prevent a race condition where we may end up overaccounting
the active state and leaving the busy-stats believing the GPU is 100%
busy, lock out the tasklet while we reconstruct the busy state. There is
no direct spinlock guard for the execlists->port[], so we need to
utilise tasklet_disable() as a synchronous barrier to prevent it, the
only writer to execlists->port[], from running at the same time as the
enable.

Fixes: 4900727d35bb ("drm/i915/pmu: Reconstruct active state on starting busy-stats")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180115092041.13509-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
(cherry picked from commit 99e48bf98dd036090b480a12c39e8b971731247e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180213095747.2424-1-tvrtko.ursulin@linux.intel.com
drivers/gpu/drm/i915/intel_engine_cs.c