[PATCH] RCU: Expedite grace periods during suspend/resume

[Borislav Petkov]

Paul says CONFIG_RCU_FAST_NO_HZ can increase grace-period durations by a
factor of four. This, in turn, can change timings during suspend and can
delay interrupts handling, leading to "IRQ XX: nobody cared" splats and
the machine disabling those interrupt lines for no sensible reason.

Thus, we want to temporarily switch to expedited grace periods when
suspending the box and return to normal settings when resuming. This
patch does exactly that.

Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 kernel/rcutree.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 986d1d3a34f5..9e9aeb38b7a2 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -53,6 +53,7 @@
 #include <linux/delay.h>
 #include <linux/stop_machine.h>
 #include <linux/random.h>
+#include <linux/suspend.h>
 
 #include "rcutree.h"
 #include <trace/events/rcu.h>
@@ -3097,6 +3098,22 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
 	return NOTIFY_OK;
 }
 
+static int rcu_pm_notify(struct notifier_block *self,
+			 unsigned long action, void *hcpu)
+{
+	switch (action) {
+	case PM_HIBERNATION_PREPARE:
+		rcu_expedited = 1;
+		break;
+	case PM_POST_RESTORE:
+		rcu_expedited = 0;
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
 /*
  * Spawn the kthread that handles this RCU flavor's grace periods.
  */
@@ -3323,6 +3340,7 @@ void __init rcu_init(void)
 	 * or the scheduler are operational.
 	 */
 	cpu_notifier(rcu_cpu_notify, 0);
+	pm_notifier(rcu_pm_notify, 0);
 	for_each_online_cpu(cpu)
 		rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
 }
-- 
1.8.2.135.g7b592fa


-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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