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Message-ID: <1337561221.2458.1.camel@pasglop>
Date: Mon, 21 May 2012 10:47:01 +1000
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>
Cc: Li Zhong <zhong@...ux.vnet.ibm.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Paul Mackerras <paulus@...ba.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
PowerPC email list <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] cpuidle: (POWER) Replace pseries_notify_cpuidle_add
call with a elegant notifier to fix lockdep problem in start_secondary
On Fri, 2012-05-18 at 18:58 +0530, Deepthi Dharwar wrote:
> 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@...ux.vnet.ibm.com>
> ---
Any reason why you don't do cpuidle_disable_device() when the
CPU is going offline and cpuidle_enable_device() when it's coming
back ?
I'm applying the patch for now since it fixes a real problem but
if the above makes sense, please send a followup fix.
Cheers,
Ben.
> arch/powerpc/include/asm/processor.h | 2 --
> arch/powerpc/platforms/pseries/processor_idle.c | 25
> +++++++++++++++++------
> arch/powerpc/platforms/pseries/smp.c | 1 -
> 3 files changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/processor.h
> b/arch/powerpc/include/asm/processor.h
> index 8e2d037..c6bc22b 100644
> --- a/arch/powerpc/include/asm/processor.h
> +++ b/arch/powerpc/include/asm/processor.h
> @@ -390,10 +390,8 @@ void cpu_idle_wait(void);
>
> #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 41a34bc..d1a7dc0 100644
> --- a/arch/powerpc/platforms/pseries/processor_idle.c
> +++ b/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;
> 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)
--
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