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Message-ID: <4FEB31E1.2030209@linux.vnet.ibm.com>
Date: Wed, 27 Jun 2012 21:46:33 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
CC: trenn@...e.de, linaro-dev@...ts.linaro.org,
linux-pm@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
linux-pm@...ts.linux-foundation.org
Subject: Re: [linux-pm] [PATCH] acpi: intel_idle : break dependency between
modules
On 06/27/2012 02:37 PM, Daniel Lezcano wrote:
> When the system is booted with some cpus offline, the idle
> driver is not initialized. When a cpu is set online, the
> acpi code call the intel idle init function. Unfortunately
> this code introduce a dependency between intel_idle and acpi.
>
> This patch is intended to remove this dependency by using the
> notifier of intel_idle. In order to make it work, the notifier
> must be initialized in the right order, acpi then intel_idle.
> This is done in the Makefile.
There is a much better way of doing this. See below.
> This patch has the benefit of
> encapsulating the intel_idle driver and remove some exported
> functions.
>
Nice :)
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
> drivers/Makefile | 3 ++-
> drivers/acpi/processor_driver.c | 7 -------
> drivers/idle/intel_idle.c | 22 ++++++++++++++--------
> include/linux/cpuidle.h | 7 -------
> 4 files changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 2ba29ff..a2454b8 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -12,8 +12,9 @@ obj-$(CONFIG_PCI) += pci/
> obj-$(CONFIG_PARISC) += parisc/
> obj-$(CONFIG_RAPIDIO) += rapidio/
> obj-y += video/
> -obj-y += idle/
> +# acpi must come before idle for initialization
> obj-$(CONFIG_ACPI) += acpi/
> +obj-y += idle/
> obj-$(CONFIG_SFI) += sfi/
> # PnP must come after ACPI since it will eventually need to check if acpi
> # was used and do nothing if so
OK, so all you are trying to do here is ensure that the intel idle related
notifier runs _after_ the acpi related one. To do that, you don't have to touch
the Makefiles at all! Just use the appropriate priorities for the notifiers
(default is 0), to handle the dependency. You can find some examples in kernel/
sched/core.c. And while doing that you might want to add a separate notifier
in intel idle rather than piggy back on the existing timer related one (because
you are handling a dependency here, which might not apply to timers, or even
worse, cause unwanted side-effects, if any).
I'll take a look at the rest of the patch tomorrow. I think Thomas has already
pointed out the rest of the issues.
Regards,
Srivatsa S. Bhat
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index 0734086..8648b29 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -427,18 +427,11 @@ static int acpi_cpu_soft_notify(struct notifier_block *nfb,
> * Initialize missing things
> */
> if (pr->flags.need_hotplug_init) {
> - struct cpuidle_driver *idle_driver =
> - cpuidle_get_driver();
> -
> printk(KERN_INFO "Will online and init hotplugged "
> "CPU: %d\n", pr->id);
> WARN(acpi_processor_start(pr), "Failed to start CPU:"
> " %d\n", pr->id);
> pr->flags.need_hotplug_init = 0;
> - if (idle_driver && !strcmp(idle_driver->name,
> - "intel_idle")) {
> - intel_idle_cpu_init(pr->id);
> - }
> /* Normal CPU soft online event */
> } else {
> acpi_processor_ppc_has_changed(pr, 0);
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index d0f59c3..4c36039 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -96,6 +96,7 @@ static const struct idle_cpu *icpu;
> static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
> static int intel_idle(struct cpuidle_device *dev,
> struct cpuidle_driver *drv, int index);
> +static int intel_idle_cpu_init(int cpu);
>
> static struct cpuidle_state *cpuidle_state_table;
>
> @@ -302,22 +303,28 @@ static void __setup_broadcast_timer(void *arg)
> clockevents_notify(reason, &cpu);
> }
>
> -static int setup_broadcast_cpuhp_notify(struct notifier_block *n,
> - unsigned long action, void *hcpu)
> +static int cpu_hotplug_notify(struct notifier_block *n,
> + unsigned long action, void *hcpu)
> {
> int hotcpu = (unsigned long)hcpu;
> + struct cpuidle_device *dev;
>
> switch (action & 0xf) {
> case CPU_ONLINE:
> smp_call_function_single(hotcpu, __setup_broadcast_timer,
> (void *)true, 1);
> +
> + dev = per_cpu_ptr(intel_idle_cpuidle_devices, hotcpu);
> + if (!dev->registered)
> + intel_idle_cpu_init(hotcpu);
> +
> break;
> }
> return NOTIFY_OK;
> }
>
> -static struct notifier_block setup_broadcast_notifier = {
> - .notifier_call = setup_broadcast_cpuhp_notify,
> +static struct notifier_block cpu_hotplug_notifier = {
> + .notifier_call = cpu_hotplug_notify,
> };
>
> static void auto_demotion_disable(void *dummy)
> @@ -407,7 +414,7 @@ static int intel_idle_probe(void)
> lapic_timer_reliable_states = LAPIC_TIMER_ALWAYS_RELIABLE;
> else {
> on_each_cpu(__setup_broadcast_timer, (void *)true, 1);
> - register_cpu_notifier(&setup_broadcast_notifier);
> + register_cpu_notifier(&cpu_hotplug_notifier);
> }
>
> pr_debug(PREFIX "v" INTEL_IDLE_VERSION
> @@ -494,7 +501,7 @@ static int intel_idle_cpuidle_driver_init(void)
> * allocate, initialize, register cpuidle_devices
> * @cpu: cpu/core to initialize
> */
> -int intel_idle_cpu_init(int cpu)
> +static int intel_idle_cpu_init(int cpu)
> {
> int cstate;
> struct cpuidle_device *dev;
> @@ -539,7 +546,6 @@ int intel_idle_cpu_init(int cpu)
>
> return 0;
> }
> -EXPORT_SYMBOL_GPL(intel_idle_cpu_init);
>
> static int __init intel_idle_init(void)
> {
> @@ -583,7 +589,7 @@ static void __exit intel_idle_exit(void)
>
> if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) {
> on_each_cpu(__setup_broadcast_timer, (void *)false, 1);
> - unregister_cpu_notifier(&setup_broadcast_notifier);
> + unregister_cpu_notifier(&cpu_hotplug_notifier);
> }
>
> return;
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 5ab7183..66d7e0d 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -213,14 +213,7 @@ struct cpuidle_governor {
> extern int cpuidle_register_governor(struct cpuidle_governor *gov);
> extern void cpuidle_unregister_governor(struct cpuidle_governor *gov);
>
> -#ifdef CONFIG_INTEL_IDLE
> -extern int intel_idle_cpu_init(int cpu);
> #else
> -static inline int intel_idle_cpu_init(int cpu) { return -1; }
> -#endif
> -
> -#else
> -static inline int intel_idle_cpu_init(int cpu) { return -1; }
>
> static inline int cpuidle_register_governor(struct cpuidle_governor *gov)
> {return 0;}
>
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