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 <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/Y8Z31UbzG3LJgAXE@hirez.programming.kicks-ass.net

--

1 files changed, 11 insertions, 1 deletions

diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index e7163f31f716..0fbdf5fe64d8 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -4,6 +4,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/pgtable.h>
+#include <linux/cpuidle.h>
 #include <asm/alternative.h>
 #include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
@@ -104,6 +105,10 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
 	 * From this point debug exceptions are disabled to prevent
 	 * updates to mdscr register (saved and restored along with
 	 * general purpose registers) from kernel debuggers.
+	 *
+	 * Strictly speaking the trace_hardirqs_off() here is superfluous,
+	 * hardirqs should be firmly off by now. This really ought to use
+	 * something like raw_local_daif_save().
 	 */
 	flags = local_daif_save();
 
@@ -120,6 +125,8 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
 	 */
 	arm_cpuidle_save_irq_context(&context);
 
+	ct_cpuidle_enter();
+
 	if (__cpu_suspend_enter(&state)) {
 		/* Call the suspend finisher */
 		ret = fn(arg);
@@ -133,8 +140,11 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
 		 */
 		if (!ret)
 			ret = -EOPNOTSUPP;
+
+		ct_cpuidle_exit();
 	} else {
-		RCU_NONIDLE(__cpu_suspend_exit());
+		ct_cpuidle_exit();
+		__cpu_suspend_exit();
 	}
 
 	arm_cpuidle_restore_irq_context(&context);