drm/i915/execlists: Relax the locked clear_bit(IRQ_EXECLIST)
authorChris Wilson <chris@chris-wilson.co.uk>
Thu, 23 Mar 2017 13:48:03 +0000 (13:48 +0000)
committerChris Wilson <chris@chris-wilson.co.uk>
Thu, 23 Mar 2017 22:13:51 +0000 (22:13 +0000)
commit2e70b8c6bf0003bf1691ac5cab5aff128747d494
tree3e5305d47eb23cb88529fa6cc9637cf748c01c65
parent292889e1ffa8bb56fda2c6208d3f884ce97e1189
drm/i915/execlists: Relax the locked clear_bit(IRQ_EXECLIST)

We only need to care about the ordering of the clearing of the bit with
the uncached CSB read in order to correctly detect a new interrupt
before the read completes. The uncached read itself acts as a full
memory barrier, so we do not need to enforce another in the form of a
locked clear_bit.

v2: Clarify why the split and unlocked test/clear is harmless.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170323134803.10418-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
drivers/gpu/drm/i915/intel_lrc.c