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Message-id: <alpine.LFD.2.02.1108031341200.22067@x980>
Date: Wed, 03 Aug 2011 13:45:32 -0400 (EDT)
From: Len Brown <lenb@...nel.org>
To: Trinabh Gupta <trinabh@...ux.vnet.ibm.com>
Cc: linux-pm@...ts.linux-foundation.org, linuxppc-dev@...abs.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V1 3/7] cpuidle: stop using pm_idle
On Tue, 7 Jun 2011, Trinabh Gupta wrote:
> From: Len Brown <len.brown@...el.com>
>
> pm_idle does not scale as an idle handler registration mechanism.
> Don't use it for cpuidle. Instead, call cpuidle directly, and
> allow architectures to use pm_idle as an arch-specific default
> if they need it. ie.
>
> cpu_idle()
> ...
> if(cpuidle_call_idle())
Looks like you forgot to correct my typo that you pointed out earlier,
s/cpuidle_call_idle/cpuidle_idle_call/
both in the comment here and for arm and sh below.
Thanks for including the From: above, that is correct form.
But note in the future that when you modify somebody else's patch,
you should append a note about what you changed,
and also add your signed-off-by, so we can
track the changes.
thanks,
-Len
> pm_idle();
>
> cc: x86@...nel.org
> cc: Kevin Hilman <khilman@...prootsystems.com>
> cc: Paul Mundt <lethal@...ux-sh.org>
> Signed-off-by: Len Brown <len.brown@...el.com>
>
> ---
>
> arch/arm/kernel/process.c | 4 +++-
> arch/sh/kernel/idle.c | 6 ++++--
> arch/x86/kernel/process_32.c | 4 +++-
> arch/x86/kernel/process_64.c | 4 +++-
> drivers/cpuidle/cpuidle.c | 39 ++++++++++++++++++---------------------
> include/linux/cpuidle.h | 2 ++
> 6 files changed, 33 insertions(+), 26 deletions(-)
>
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index 5e1e541..d7ee0d4 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -30,6 +30,7 @@
> #include <linux/uaccess.h>
> #include <linux/random.h>
> #include <linux/hw_breakpoint.h>
> +#include <linux/cpuidle.h>
>
> #include <asm/cacheflush.h>
> #include <asm/leds.h>
> @@ -196,7 +197,8 @@ void cpu_idle(void)
> cpu_relax();
> } else {
> stop_critical_timings();
> - pm_idle();
> + if (cpuidle_call_idle())
> + pm_idle();
> start_critical_timings();
> /*
> * This will eventually be removed - pm_idle
> diff --git a/arch/sh/kernel/idle.c b/arch/sh/kernel/idle.c
> index 425d604..9c7099e 100644
> --- a/arch/sh/kernel/idle.c
> +++ b/arch/sh/kernel/idle.c
> @@ -16,12 +16,13 @@
> #include <linux/thread_info.h>
> #include <linux/irqflags.h>
> #include <linux/smp.h>
> +#include <linux/cpuidle.h>
> #include <asm/pgalloc.h>
> #include <asm/system.h>
> #include <asm/atomic.h>
> #include <asm/smp.h>
>
> -void (*pm_idle)(void) = NULL;
> +static void (*pm_idle)(void);
>
> static int hlt_counter;
>
> @@ -100,7 +101,8 @@ void cpu_idle(void)
> local_irq_disable();
> /* Don't trace irqs off for idle */
> stop_critical_timings();
> - pm_idle();
> + if (cpuidle_call_idle())
> + pm_idle();
> /*
> * Sanity check to ensure that pm_idle() returns
> * with IRQs enabled
> diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
> index 8d12878..61fadbe 100644
> --- a/arch/x86/kernel/process_32.c
> +++ b/arch/x86/kernel/process_32.c
> @@ -38,6 +38,7 @@
> #include <linux/uaccess.h>
> #include <linux/io.h>
> #include <linux/kdebug.h>
> +#include <linux/cpuidle.h>
>
> #include <asm/pgtable.h>
> #include <asm/system.h>
> @@ -109,7 +110,8 @@ void cpu_idle(void)
> local_irq_disable();
> /* Don't trace irqs off for idle */
> stop_critical_timings();
> - pm_idle();
> + if (cpuidle_idle_call())
> + pm_idle();
> start_critical_timings();
> }
> tick_nohz_restart_sched_tick();
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index 6c9dd92..62c219a 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -37,6 +37,7 @@
> #include <linux/uaccess.h>
> #include <linux/io.h>
> #include <linux/ftrace.h>
> +#include <linux/cpuidle.h>
>
> #include <asm/pgtable.h>
> #include <asm/system.h>
> @@ -136,7 +137,8 @@ void cpu_idle(void)
> enter_idle();
> /* Don't trace irqs off for idle */
> stop_critical_timings();
> - pm_idle();
> + if (cpuidle_idle_call())
> + pm_idle();
> start_critical_timings();
>
> /* In many cases the interrupt that ended idle
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 8d7303b..304e378 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -25,10 +25,10 @@ DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
>
> DEFINE_MUTEX(cpuidle_lock);
> LIST_HEAD(cpuidle_detected_devices);
> -static void (*pm_idle_old)(void);
>
> static int enabled_devices;
> static int off __read_mostly;
> +static int initialized __read_mostly;
>
> int cpuidle_disabled(void)
> {
> @@ -56,27 +56,24 @@ static int __cpuidle_register_device(struct cpuidle_device *dev);
> * cpuidle_idle_call - the main idle loop
> *
> * NOTE: no locks or semaphores should be used here
> + * return non-zero on failure
> */
> -static void cpuidle_idle_call(void)
> +int cpuidle_idle_call(void)
> {
> struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
> struct cpuidle_driver *drv = cpuidle_get_driver();
> struct cpuidle_state *target_state;
> int next_state, entered_state;
>
> - /* check if the device is ready */
> - if (!dev || !dev->enabled) {
> - if (pm_idle_old)
> - pm_idle_old();
> - else
> -#if defined(CONFIG_ARCH_HAS_DEFAULT_IDLE)
> - default_idle();
> -#else
> - local_irq_enable();
> -#endif
> - return;
> - }
> + if (off)
> + return -ENODEV;
> +
> + if (!initialized)
> + return -ENODEV;
>
> + /* check if the device is ready */
> + if (!dev || !dev->enabled)
> + return -EBUSY;
> #if 0
> /* shows regressions, re-enable for 2.6.29 */
> /*
> @@ -90,7 +87,7 @@ static void cpuidle_idle_call(void)
> next_state = cpuidle_curr_governor->select(drv, dev);
> if (need_resched()) {
> local_irq_enable();
> - return;
> + return 0;
> }
>
> target_state = &drv->states[next_state];
> @@ -116,6 +113,8 @@ static void cpuidle_idle_call(void)
> /* give the governor an opportunity to reflect on the outcome */
> if (cpuidle_curr_governor->reflect)
> cpuidle_curr_governor->reflect(dev, entered_state);
> +
> + return 0;
> }
>
> /**
> @@ -123,10 +122,10 @@ static void cpuidle_idle_call(void)
> */
> void cpuidle_install_idle_handler(void)
> {
> - if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
> + if (enabled_devices) {
> /* Make sure all changes finished before we switch to new idle */
> smp_wmb();
> - pm_idle = cpuidle_idle_call;
> + initialized = 1;
> }
> }
>
> @@ -135,8 +134,8 @@ void cpuidle_install_idle_handler(void)
> */
> void cpuidle_uninstall_idle_handler(void)
> {
> - if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
> - pm_idle = pm_idle_old;
> + if (enabled_devices) {
> + initialized = 0;
> cpuidle_kick_cpus();
> }
> }
> @@ -410,8 +409,6 @@ static int __init cpuidle_init(void)
> if (cpuidle_disabled())
> return -ENODEV;
>
> - pm_idle_old = pm_idle;
> -
> ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
> if (ret)
> return ret;
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 2786787..c904188 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -128,6 +128,7 @@ struct cpuidle_driver {
>
> #ifdef CONFIG_CPU_IDLE
> extern void disable_cpuidle(void);
> +extern int cpuidle_idle_call(void);
>
> extern int cpuidle_register_driver(struct cpuidle_driver *drv);
> struct cpuidle_driver *cpuidle_get_driver(void);
> @@ -142,6 +143,7 @@ extern void cpuidle_disable_device(struct cpuidle_device *dev);
>
> #else
> static inline void disable_cpuidle(void) { }
> +static inline int cpuidle_idle_call(void) { return -ENODEV; }
>
> static inline int cpuidle_register_driver(struct cpuidle_driver *drv)
> {return -ENODEV; }
>
> --
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