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Message-Id: <201206271506.29034.trenn@suse.de>
Date: Wed, 27 Jun 2012 15:06:28 +0200
From: Thomas Renninger <trenn@...e.de>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: srivatsa.bhat@...ux.vnet.ibm.com, deepthi@...ux.vnet.ibm.com,
linux-acpi@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
linux-pm@...r.kernel.org, lenb@...nel.org, rjw@...k.pl,
x86@...nel.org, linux-kernel@...r.kernel.org,
linaro-dev@...ts.linaro.org
Subject: Re: [PATCH] acpi: intel_idle : break dependency between modules
Hi,
I agree that such a dependency between 2 modules is not
nice. But your patch will have bad side-effects (see comments
embedded below).
On Wednesday, June 27, 2012 11:07:48 AM 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. This patch has the benefit of
> encapsulating the intel_idle driver and remove some exported
> functions.
>
> 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/
This breaks intel_idle.
Loading order defines which one comes first and is used: intel_idle
or ACPI processor cpuidle driver.
With above, one would get acpi_idle cpuidle driver if both are
compiled in, instead of the intel_idle one.
Why exactly is this necessary, couldn't it just work?
> 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
> 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);
> +
A small comment why this can happen and needs to be done
(real hotplugged cpu case) might help here later.
> 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);
The notifier always has to be registered now, not only in:
if (boot_cpu_has(X86_FEATURE_ARAT)) /* Always Reliable APIC Timer */
case.
> }
>
> 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);
Same.
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