kernel/x86-Avoid-invoking-RCU-when-CPU-is-idle.patch

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 15763af..f6978b0 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -386,17 +386,21 @@ void default_idle(void)
 		 */
 		smp_mb();
 
+		rcu_idle_enter();
 		if (!need_resched())
 			safe_halt();	/* enables interrupts racelessly */
 		else
 			local_irq_enable();
+		rcu_idle_exit();
 		current_thread_info()->status |= TS_POLLING;
 		trace_power_end(smp_processor_id());
 		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
 	} else {
 		local_irq_enable();
 		/* loop is done by the caller */
+		rcu_idle_enter();
 		cpu_relax();
+		rcu_idle_exit();
 	}
 }
 #ifdef CONFIG_APM_MODULE
@@ -457,14 +461,19 @@ static void mwait_idle(void)
 
 		__monitor((void *)&current_thread_info()->flags, 0, 0);
 		smp_mb();
+		rcu_idle_enter();
 		if (!need_resched())
 			__sti_mwait(0, 0);
 		else
 			local_irq_enable();
+		rcu_idle_exit();
 		trace_power_end(smp_processor_id());
 		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
-	} else
+	} else {
 		local_irq_enable();
+		rcu_idle_enter();
+		rcu_idle_exit();
+	}
 }
 
 /*
@@ -477,8 +486,10 @@ static void poll_idle(void)
 	trace_power_start(POWER_CSTATE, 0, smp_processor_id());
 	trace_cpu_idle(0, smp_processor_id());
 	local_irq_enable();
+	rcu_idle_enter();
 	while (!need_resched())
 		cpu_relax();
+	rcu_idle_exit();
 	trace_power_end(smp_processor_id());
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
 }
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 485204f..6d9d4d5 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -100,7 +100,6 @@ void cpu_idle(void)
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_idle_enter();
-		rcu_idle_enter();
 		while (!need_resched()) {
 
 			check_pgt_cache();
@@ -117,7 +116,6 @@ void cpu_idle(void)
 				pm_idle();
 			start_critical_timings();
 		}
-		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		preempt_enable_no_resched();
 		schedule();
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 9b9fe4a..55a1a35 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -140,13 +140,9 @@ void cpu_idle(void)
 			/* Don't trace irqs off for idle */
 			stop_critical_timings();
 
-			/* enter_idle() needs rcu for notifiers */
-			rcu_idle_enter();
-
 			if (cpuidle_idle_call())
 				pm_idle();
 
-			rcu_idle_exit();
 			start_critical_timings();
 
 			/* In many cases the interrupt that ended idle
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 20bce51..a9ddab8 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -261,6 +261,7 @@ static int intel_idle(struct cpuidle_device *dev,
 	kt_before = ktime_get_real();
 
 	stop_critical_timings();
+	rcu_idle_enter();
 	if (!need_resched()) {
 
 		__monitor((void *)&current_thread_info()->flags, 0, 0);
@@ -268,6 +269,7 @@ static int intel_idle(struct cpuidle_device *dev,
 		if (!need_resched())
 			__mwait(eax, ecx);
 	}
+	rcu_idle_exit();
 
 	start_critical_timings();