powerpc/pseries/cpuidle: Replace pseries_notify_cpuidle_add call with…

… notifier

The following patch is to remove the pseries_notify_add_cpu() call
and replace it by a hot plug notifier.

This would prevent cpuidle resources being released and allocated each
time cpu comes online on pseries.

The earlier design was causing a lockdep problem
in start_secondary as reported on this thread
	-https://lkml.org/lkml/2012/5/17/2

This applies on 3.4-rc7

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/processor.h

@@ -389,10 +389,8 @@ extern int powersave_nap;	/* set if nap mode can be used in idle loop */
 
 #ifdef CONFIG_PSERIES_IDLE
 extern void update_smt_snooze_delay(int snooze);
-extern int pseries_notify_cpuidle_add_cpu(int cpu);
 #else
 static inline void update_smt_snooze_delay(int snooze) {}
-static inline int pseries_notify_cpuidle_add_cpu(int cpu) { return 0; }
 #endif
 
 extern void flush_instruction_cache(void);

arch/powerpc/platforms/pseries/processor_idle.c

@@ -11,6 +11,7 @@
 #include <linux/moduleparam.h>
 #include <linux/cpuidle.h>
 #include <linux/cpu.h>
+#include <linux/notifier.h>
 
 #include <asm/paca.h>
 #include <asm/reg.h>
@@ -186,17 +187,28 @@ static struct cpuidle_state shared_states[MAX_IDLE_STATE_COUNT] = {
 		.enter = &shared_cede_loop },
 };
 
-int pseries_notify_cpuidle_add_cpu(int cpu)
+static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
+			unsigned long action, void *hcpu)
 {
+	int hotcpu = (unsigned long)hcpu;
 	struct cpuidle_device *dev =
-			per_cpu_ptr(pseries_cpuidle_devices, cpu);
-	if (dev && cpuidle_get_driver()) {
-		cpuidle_disable_device(dev);
-		cpuidle_enable_device(dev);
+			per_cpu_ptr(pseries_cpuidle_devices, hotcpu);
+
+	switch (action & 0xf) {
+	case CPU_ONLINE:
+		if (dev && cpuidle_get_driver()) {
+			cpuidle_disable_device(dev);
+			cpuidle_enable_device(dev);
+		}
+		break;
 	}
-	return 0;
+	return NOTIFY_OK;
 }
 
+static struct notifier_block setup_hotplug_notifier = {
+	.notifier_call = pseries_cpuidle_add_cpu_notifier,
+};
+
 /*
  * pseries_cpuidle_driver_init()
  */
@@ -321,6 +333,7 @@ static int __init pseries_processor_idle_init(void)
 		return retval;
 	}
 
+	register_cpu_notifier(&setup_hotplug_notifier);
 	printk(KERN_DEBUG "pseries_idle_driver registered\n");
 
 	return 0;

arch/powerpc/platforms/pseries/smp.c

@@ -147,7 +147,6 @@ static void __devinit smp_xics_setup_cpu(int cpu)
 	set_cpu_current_state(cpu, CPU_STATE_ONLINE);
 	set_default_offline_state(cpu);
 #endif
-	pseries_notify_cpuidle_add_cpu(cpu);
 }
 
 static int __devinit smp_pSeries_kick_cpu(int nr)