cpuidle, arm64: Fix the ARM64 cpuidle logic

The recent cpuidle changes started triggering RCU splats on
Juno development boards:

  | =============================
  | WARNING: suspicious RCU usage
  | -----------------------------
  | include/trace/events/ipi.h:19 suspicious rcu_dereference_check() usage!

Fix cpuidle on ARM64:

 - ... by introducing a new 'is_rcu' flag to the cpuidle helpers & make
   ARM64 use it, as ARM64 wants to keep RCU active longer and wants to
   do the ct_cpuidle_enter()/exit() dance itself.

 - Also update the PSCI driver accordingly.

 - This also removes the last known RCU_NONIDLE() user as a bonus.

Reported-by: Mark Rutland <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Tested-by: Sudeep Holla <[email protected]>
Tested-by: Mark Rutland <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

--

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index e7bcfca4159f..f3a044fa4652 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -462,11 +462,22 @@ int psci_cpu_suspend_enter(u32 state)
 	if (!psci_power_state_loses_context(state)) {
 		struct arm_cpuidle_irq_context context;
 
+		ct_cpuidle_enter();
 		arm_cpuidle_save_irq_context(&context);
 		ret = psci_ops.cpu_suspend(state, 0);
 		arm_cpuidle_restore_irq_context(&context);
+		ct_cpuidle_exit();
 	} else {
+		/*
+		 * ARM64 cpu_suspend() wants to do ct_cpuidle_*() itself.
+		 */
+		if (!IS_ENABLED(CONFIG_ARM64))
+			ct_cpuidle_enter();
+
 		ret = cpu_suspend(state, psci_suspend_finisher);
+
+		if (!IS_ENABLED(CONFIG_ARM64))
+			ct_cpuidle_exit();
 	}
 
 	return ret;