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Commit b1379d49 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Replace lockless_dereference(bool) with READ_ONCE() 



After Joonas complained about using READ_ONCE() on the only use of the
variable in the function, where the intent was to simply document that
the read was intentionally racy and unlocked, I switched the READ_ONCE()
over to lockless_dereference(). However, in linux-next that has a
stronger type-check to only allow pointers and is no longer
interchangeable with READ_ONCE(), see commit 331b6d8c
("locking/barriers: Validate lockless_dereference() is used on a pointer
type")

Reported-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Fixes: 67d97da3 ("drm/i915: Only start retire worker when idle")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1467705276-707-1-git-send-email-chris@chris-wilson.co.uk


Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@intel.com>
parent af1346a0

drivers/gpu/drm/i915/i915_gem.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -3290,7 +3290,7 @@ i915_gem_retire_work_handler(struct work_struct *work) 
	 * We do not need to do this test under locking as in the worst-case

	 * We do not need to do this test under locking as in the worst-case

	 * we queue the retire worker once too often.

	 * we queue the retire worker once too often.

	 */

	 */

	if (lockless_dereference(dev_priv->gt.awake))

	if (READ_ONCE(dev_priv->gt.awake))

		queue_delayed_work(dev_priv->wq,

		queue_delayed_work(dev_priv->wq,

				   &dev_priv->gt.retire_work,

				   &dev_priv->gt.retire_work,

				   round_jiffies_up_relative(HZ));

				   round_jiffies_up_relative(HZ));

drivers/gpu/drm/i915/i915_irq.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -3095,7 +3095,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work) 
	if (!i915.enable_hangcheck)

	if (!i915.enable_hangcheck)

		return;

		return;





	if (!lockless_dereference(dev_priv->gt.awake))

	if (!READ_ONCE(dev_priv->gt.awake))

		return;

		return;





	/* As enabling the GPU requires fairly extensive mmio access,

	/* As enabling the GPU requires fairly extensive mmio access,