Quoting Tvrtko Ursulin (2020-11-20 09:56:35)
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> Guc->mmio_msg is set under the guc->irq_lock in guc_get_mmio_msg so it
> should be consumed under the same lock from guc_handle_mmio_msg.
>
> I am not sure if the overall flow here makes complete sense but at least
> the correct lock is now used.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/uc/intel_uc.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> index 4e6070e95fe9..220626c3ad81 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> @@ -175,19 +175,15 @@ static void guc_get_mmio_msg(struct intel_guc *guc)
>
> static void guc_handle_mmio_msg(struct intel_guc *guc)
> {
> - struct drm_i915_private *i915 = guc_to_gt(guc)->i915;
> -
> /* we need communication to be enabled to reply to GuC */
> GEM_BUG_ON(!guc_communication_enabled(guc));
>
> - if (!guc->mmio_msg)
> - return;
> -
> - spin_lock_irq(&i915->irq_lock);
> - intel_guc_to_host_process_recv_msg(guc, &guc->mmio_msg, 1);
> - spin_unlock_irq(&i915->irq_lock);
> -
> - guc->mmio_msg = 0;
> + spin_lock_irq(&guc->irq_lock);
> + if (guc->mmio_msg) {
> + intel_guc_to_host_process_recv_msg(guc, &guc->mmio_msg, 1);
> + guc->mmio_msg = 0;
> + }
> + spin_unlock_irq(&guc->irq_lock);
Based on just looking at mmio_msg, the locking should be guc->irq_lock, and
guc->mmio_msg = 0 should be pulled under the lock.
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris
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