On Fri, Apr 05, 2024 at 04:18:27PM +0200, Sebastian Andrzej Siewior wrote:
> intel_guc_send_busy_loop() looks at in_atomic() and irqs_disabled() to
> decide if it should busy-spin while waiting or if it may sleep.
> Both checks will report false on PREEMPT_RT if sleeping spinlocks are
> acquired leading to RCU splats while the function sleeps.
>
> Check also if RCU has been disabled.
>
> Reported-by: "John B. Wyatt IV" <jwyatt@xxxxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/uc/intel_guc.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> index be70c46604b49..387cc1911302f 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> @@ -360,7 +360,7 @@ static inline int intel_guc_send_busy_loop(struct intel_guc *guc,
> {
> int err;
> unsigned int sleep_period_ms = 1;
> - bool not_atomic = !in_atomic() && !irqs_disabled();
> + bool not_atomic = !in_atomic() && !irqs_disabled() && !rcu_preempt_depth();
>
> /*
> * FIXME: Have caller pass in if we are in an atomic context to avoid
> --
> 2.43.0
>
