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Subject[PATCH v3] cpuidle: (POWER) Replace pseries_notify_cpuidle_add _cpu call with a notifier to fix lockdep problem in start_secondary

cpuidle: (POWER) Replace pseries_notify_cpuidle_add_cpu call with a notifier to fix lockdep problem in start_secondary

From: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>

Currently the call to pseries_notify_cpuidle_add_cpu(), that takes
action on the cpuidle front when a cpu is added/removed
is being made from smp_xics_setup_cpu().
This caused lockdep issues as
reported https://lkml.org/lkml/2012/5/17/2

On addition of each cpu, resources are cleared and re-allocated
each time, all in critical section as part of start_secondary()
call which has interrupts disabled.
To resolve this issue, the pseries_notify_cpuidle_add_cpu() call is
is now being replaced by a hotplug notifier which
would prevent cpuidle resources from being
released and allocated each time cpu is onlined in the critical code path.

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

---
This patch has in-corporated review comments
received on the earlier version posted.
v1 -> https://lkml.org/lkml/2012/5/18/174
v2 -> https://lkml.org/lkml/2012/7/3/61
This applies on 3.5-rc5

arch/powerpc/include/asm/processor.h | 2 -
arch/powerpc/platforms/pseries/processor_idle.c | 35 ++++++++++++++++++++---
arch/powerpc/platforms/pseries/smp.c | 1 -
3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 413a5ea..53b6dfa 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/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);
diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c
index e61483e..da245c0 100644
--- a/arch/powerpc/platforms/pseries/processor_idle.c
+++ b/arch/powerpc/platforms/pseries/processor_idle.c
@@ -186,17 +186,40 @@ 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);
+ per_cpu_ptr(pseries_cpuidle_devices, hotcpu);
+
if (dev && cpuidle_get_driver()) {
- cpuidle_disable_device(dev);
- cpuidle_enable_device(dev);
+ switch (action) {
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
+ cpuidle_pause_and_lock();
+ cpuidle_enable_device(dev);
+ cpuidle_resume_and_unlock();
+ break;
+
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ cpuidle_pause_and_lock();
+ cpuidle_disable_device(dev);
+ cpuidle_resume_and_unlock();
+ break;
+
+ default:
+ return NOTIFY_DONE;
+ }
}
- 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 +344,7 @@ 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;
@@ -329,6 +353,7 @@ static int __init pseries_processor_idle_init(void)
static void __exit pseries_processor_idle_exit(void)
{

+ unregister_cpu_notifier(&setup_hotplug_notifier);
pseries_idle_devices_uninit();
cpuidle_unregister_driver(&pseries_idle_driver);

diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index e16bb8d..71706bc 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/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)
Cheers,
Deepthi



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