Date:	Wed, 22 Feb 2012 14:15:40 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>, markgross@...gnar.org,
	Matthew Garrett <mjg@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	John Stultz <john.stultz@...aro.org>,
	Brian Swetland <swetland@...gle.com>,
	Neil Brown <neilb@...e.de>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [RFC][PATCH 5/7] PM / Sleep: Implement opportunistic sleep

On 02/22/2012 05:05 AM, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> Introduce a mechanism by which the kernel can trigger global
> transitions to a sleep state chosen by user space if there are no
> active wakeup sources.
> 
> It consists of a new sysfs attribute, /sys/power/autosleep, that
> can be written one of the strings returned by reads from
> /sys/power/state, an ordered workqueue and a work item carrying out
> the "suspend" operations.  If a string representing the system's
> sleep state is written to /sys/power/autosleep, the work item
> triggering transitions to that state is queued up and it requeues
> itself after every execution until user space writes "off" to
> /sys/power/autosleep.
> 
> That work item enables the detection of wakeup events using the
> functions already defined in drivers/base/power/wakeup.c (with one
> small modification) and calls either pm_suspend(), or hibernate() to
> put the system into a sleep state.  If a wakeup event is reported
> while the transition is in progress, it will abort the transition and
> the "system suspend" work item will be queued up again.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> ---
>  Documentation/ABI/testing/sysfs-power |   17 +++++
>  drivers/base/power/wakeup.c           |   38 ++++++-----
>  include/linux/suspend.h               |   13 +++-
>  kernel/power/Kconfig                  |    8 ++
>  kernel/power/Makefile                 |    1 
>  kernel/power/autosleep.c              |   98 ++++++++++++++++++++++++++++++
>  kernel/power/main.c                   |  108 ++++++++++++++++++++++++++++------
>  kernel/power/power.h                  |   18 +++++
>  8 files changed, 266 insertions(+), 35 deletions(-)
> 
> Index: linux/kernel/power/Makefile
> ===================================================================
> --- linux.orig/kernel/power/Makefile
> +++ linux/kernel/power/Makefile
> @@ -9,5 +9,6 @@ obj-$(CONFIG_SUSPEND)		+= suspend.o
>  obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
>  obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o \
>  				   block_io.o
> +obj-$(CONFIG_PM_AUTOSLEEP)	+= autosleep.o
> 
>  obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
> Index: linux/kernel/power/Kconfig
> ===================================================================
> --- linux.orig/kernel/power/Kconfig
> +++ linux/kernel/power/Kconfig
> @@ -103,6 +103,14 @@ config PM_SLEEP_SMP
>  	select HOTPLUG
>  	select HOTPLUG_CPU
> 
> +config PM_AUTOSLEEP
> +	bool "Opportunistic sleep"
> +	depends on PM_SLEEP
> +	default n
> +	---help---
> +	Allow the kernel to trigger a system transition into a global sleep
> +	state automatically whenever there are no active wakeup sources.
> +
>  config PM_RUNTIME
>  	bool "Run-time PM core functionality"
>  	depends on !IA64_HP_SIM
> Index: linux/kernel/power/power.h
> ===================================================================
> --- linux.orig/kernel/power/power.h
> +++ linux/kernel/power/power.h
> @@ -264,3 +264,21 @@ static inline void suspend_thaw_processe
>  {
>  }
>  #endif
> +
> +#ifdef CONFIG_PM_AUTOSLEEP
> +
> +/* kernel/power/autosleep.c */
> +extern int pm_autosleep_init(void);
> +extern void pm_autosleep_lock(void);
> +extern void pm_autosleep_unlock(void);
> +extern suspend_state_t pm_autosleep_state(void);
> +extern int pm_autosleep_set_state(suspend_state_t state);
> +
> +#else /* !CONFIG_PM_AUTOSLEEP */
> +
> +static inline int pm_autosleep_init(void) { return 0; }
> +static inline void pm_autosleep_lock(void) {}
> +static inline void pm_autosleep_unlock(void) {}
> +static inline suspend_state_t pm_autosleep_state(void) { return PM_SUSPEND_ON; }
> +
> +#endif /* !CONFIG_PM_AUTOSLEEP */
> Index: linux/include/linux/suspend.h
> ===================================================================
> --- linux.orig/include/linux/suspend.h
> +++ linux/include/linux/suspend.h
> @@ -356,7 +356,7 @@ extern int unregister_pm_notifier(struct
>  extern bool events_check_enabled;
> 
>  extern bool pm_wakeup_pending(void);
> -extern bool pm_get_wakeup_count(unsigned int *count);
> +extern bool pm_get_wakeup_count(unsigned int *count, bool block);
>  extern bool pm_save_wakeup_count(unsigned int count);
> 
>  static inline void lock_system_sleep(void)
> @@ -407,6 +407,17 @@ static inline void unlock_system_sleep(v
> 
>  #endif /* !CONFIG_PM_SLEEP */
> 
> +#ifdef CONFIG_PM_AUTOSLEEP
> +
> +/* kernel/power/autosleep.c */
> +void queue_up_suspend_work(void);
> +
> +#else /* !CONFIG_PM_AUTOSLEEP */
> +
> +static inline void queue_up_suspend_work(void) {}
> +
> +#endif /* !CONFIG_PM_AUTOSLEEP */
> +
>  #ifdef CONFIG_ARCH_SAVE_PAGE_KEYS
>  /*
>   * The ARCH_SAVE_PAGE_KEYS functions can be used by an architecture
> Index: linux/kernel/power/autosleep.c
> ===================================================================
> --- /dev/null
> +++ linux/kernel/power/autosleep.c
> @@ -0,0 +1,98 @@
> +/*
> + * kernel/power/autosleep.c
> + *
> + * Opportunistic sleep support.
> + *
> + * Copyright (C) 2012 Rafael J. Wysocki <rjw@...k.pl>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/mutex.h>
> +#include <linux/pm_wakeup.h>
> +
> +#include "power.h"
> +
> +static suspend_state_t autosleep_state;
> +static struct workqueue_struct *autosleep_wq;
> +static DEFINE_MUTEX(autosleep_lock);
> +
> +static void try_to_suspend(struct work_struct *work)
> +{
> +	unsigned int initial_count, final_count;
> +
> +	if (!pm_get_wakeup_count(&initial_count, true))
> +		goto out;
> +
> +	mutex_lock(&autosleep_lock);
> +
> +	if (!pm_save_wakeup_count(initial_count)) {
> +		mutex_unlock(&autosleep_lock);
> +		goto out;
> +	}
> +
> +	if (autosleep_state == PM_SUSPEND_ON) {
> +		mutex_unlock(&autosleep_lock);
> +		return;
> +	}
> +	if (autosleep_state >= PM_SUSPEND_MAX)
> +		hibernate();
> +	else
> +		pm_suspend(autosleep_state);


We are calling pm_suspend() or hibernate() directly here.
Won't this break build when CONFIG_SUSPEND or CONFIG_HIBERNATION is not set?
CONFIG_PM_AUTOSLEEP depends only on PM_SLEEP which means we could enable
either one of suspend or hibernation and yet come to this point, breaking
the option which was not enabled.

Regards,
Srivatsa S. Bhat

> +
> +	mutex_unlock(&autosleep_lock);
> +
> +	if (!pm_get_wakeup_count(&final_count, false))
> +		goto out;
> +
> +	if (final_count == initial_count)
> +		schedule_timeout(HZ / 2);
> +
> + out:
> +	queue_up_suspend_work();
> +}
> +
> +static DECLARE_WORK(suspend_work, try_to_suspend);
> +
> +void queue_up_suspend_work(void)
> +{
> +	if (!work_pending(&suspend_work) && autosleep_state > PM_SUSPEND_ON)
> +		queue_work(autosleep_wq, &suspend_work);
> +}
> +
> +suspend_state_t pm_autosleep_state(void)
> +{
> +	return autosleep_state;
> +}
> +
> +int pm_autosleep_set_state(suspend_state_t state)
> +{
> +#ifndef CONFIG_HIBERNATION
> +	if (state >= PM_SUSPEND_MAX)
> +		return -EINVAL;
> +#endif
> +	mutex_lock(&autosleep_lock);
> +	if (state == PM_SUSPEND_ON && autosleep_state != PM_SUSPEND_ON) {
> +		autosleep_state = PM_SUSPEND_ON;
> +	} else if (state > PM_SUSPEND_ON) {
> +		autosleep_state = state;
> +		queue_up_suspend_work();
> +	}
> +	mutex_unlock(&autosleep_lock);
> +	return 0;
> +}
> +
> +void pm_autosleep_lock(void)
> +{
> +	mutex_lock(&autosleep_lock);
> +}
> +
> +void pm_autosleep_unlock(void)
> +{
> +	mutex_unlock(&autosleep_lock);
> +}
> +
> +int __init pm_autosleep_init(void)
> +{
> +	autosleep_wq = alloc_ordered_workqueue("autosleep", 0);
> +	return autosleep_wq ? 0 : -ENOMEM;
> +}
> Index: linux/kernel/power/main.c
> ===================================================================
> --- linux.orig/kernel/power/main.c
> +++ linux/kernel/power/main.c
> @@ -269,8 +269,7 @@ static ssize_t state_show(struct kobject
>  	return (s - buf);
>  }
> 
> -static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
> -			   const char *buf, size_t n)
> +static suspend_state_t decode_state(const char *buf, size_t n)
>  {
>  #ifdef CONFIG_SUSPEND
>  	suspend_state_t state = PM_SUSPEND_STANDBY;
> @@ -278,27 +277,43 @@ static ssize_t state_store(struct kobjec
>  #endif
>  	char *p;
>  	int len;
> -	int error = -EINVAL;
> 
>  	p = memchr(buf, '\n', n);
>  	len = p ? p - buf : n;
> 
> -	/* First, check if we are requested to hibernate */
> -	if (len == 4 && !strncmp(buf, "disk", len)) {
> -		error = hibernate();
> -		goto Exit;
> -	}
> +	/* Check hibernation first. */
> +	if (len == 4 && !strncmp(buf, "disk", len))
> +		return PM_SUSPEND_MAX;
> 
>  #ifdef CONFIG_SUSPEND
> -	for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
> -		if (*s && len == strlen(*s) && !strncmp(buf, *s, len)) {
> -			error = pm_suspend(state);
> -			break;
> -		}
> -	}
> +	for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++)
> +		if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
> +			return state;
>  #endif
> 
> - Exit:
> +	return PM_SUSPEND_ON;
> +}
> +
> +static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
> +			   const char *buf, size_t n)
> +{
> +	suspend_state_t state;
> +	int error = -EINVAL;
> +
> +	pm_autosleep_lock();
> +	if (pm_autosleep_state() > PM_SUSPEND_ON) {
> +		error = -EBUSY;
> +		goto out;
> +	}
> +
> +	state = decode_state(buf, n);
> +	if (state < PM_SUSPEND_MAX)
> +		error = pm_suspend(state);
> +	else if (state > PM_SUSPEND_ON)
> +		error = hibernate();
> +
> + out:
> +	pm_autosleep_unlock();
>  	return error ? error : n;
>  }
> 
> @@ -339,7 +354,8 @@ static ssize_t wakeup_count_show(struct
>  {
>  	unsigned int val;
> 
> -	return pm_get_wakeup_count(&val) ? sprintf(buf, "%u\n", val) : -EINTR;
> +	return pm_get_wakeup_count(&val, true) ?
> +		sprintf(buf, "%u\n", val) : -EINTR;
>  }
> 
>  static ssize_t wakeup_count_store(struct kobject *kobj,
> @@ -347,15 +363,65 @@ static ssize_t wakeup_count_store(struct
>  				const char *buf, size_t n)
>  {
>  	unsigned int val;
> +	int error = -EINVAL;
> +
> +	pm_autosleep_lock();
> +	if (pm_autosleep_state() > PM_SUSPEND_ON) {
> +		error = -EBUSY;
> +		goto out;
> +	}
> 
>  	if (sscanf(buf, "%u", &val) == 1) {
>  		if (pm_save_wakeup_count(val))
>  			return n;
>  	}
> -	return -EINVAL;
> +
> + out:
> +	pm_autosleep_unlock();
> +	return error;
>  }
> 
>  power_attr(wakeup_count);
> +
> +#ifdef CONFIG_PM_AUTOSLEEP
> +static ssize_t autosleep_show(struct kobject *kobj,
> +			      struct kobj_attribute *attr,
> +			      char *buf)
> +{
> +	suspend_state_t state = pm_autosleep_state();
> +
> +	if (state == PM_SUSPEND_ON)
> +		return sprintf(buf, "off\n");
> +
> +#ifdef CONFIG_SUSPEND
> +	if (state < PM_SUSPEND_MAX)
> +		return sprintf(buf, "%s\n", valid_state(state) ?
> +						pm_states[state] : "error");
> +#endif
> +#ifdef CONFIG_HIBERNATION
> +	return sprintf(buf, "disk\n");
> +#else
> +	return sprintf(buf, "error");
> +#endif
> +}
> +
> +static ssize_t autosleep_store(struct kobject *kobj,
> +			       struct kobj_attribute *attr,
> +			       const char *buf, size_t n)
> +{
> +	suspend_state_t state = decode_state(buf, n);
> +	int error;
> +
> +	if (state == PM_SUSPEND_ON && strncmp(buf, "off", 3)
> +	    && strncmp(buf, "off\n", 4))
> +		return -EINVAL;
> +
> +	error = pm_autosleep_set_state(state);
> +	return error ? error : n;
> +}
> +
> +power_attr(autosleep);
> +#endif /* CONFIG_PM_AUTOSLEEP */
>  #endif /* CONFIG_PM_SLEEP */
> 
>  #ifdef CONFIG_PM_TRACE
> @@ -409,6 +475,9 @@ static struct attribute * g[] = {
>  #ifdef CONFIG_PM_SLEEP
>  	&pm_async_attr.attr,
>  	&wakeup_count_attr.attr,
> +#ifdef CONFIG_PM_AUTOSLEEP
> +	&autosleep_attr.attr,
> +#endif
>  #ifdef CONFIG_PM_DEBUG
>  	&pm_test_attr.attr,
>  #endif
> @@ -444,7 +513,10 @@ static int __init pm_init(void)
>  	power_kobj = kobject_create_and_add("power", NULL);
>  	if (!power_kobj)
>  		return -ENOMEM;
> -	return sysfs_create_group(power_kobj, &attr_group);
> +	error = sysfs_create_group(power_kobj, &attr_group);
> +	if (error)
> +		return error;
> +	return pm_autosleep_init();
>  }
> 
>  core_initcall(pm_init);
> Index: linux/drivers/base/power/wakeup.c
> ===================================================================
> --- linux.orig/drivers/base/power/wakeup.c
> +++ linux/drivers/base/power/wakeup.c
> @@ -492,8 +492,10 @@ static void wakeup_source_deactivate(str
>  	atomic_add(MAX_IN_PROGRESS, &combined_event_count);
> 
>  	split_counters(&cnt, &inpr);
> -	if (!inpr && waitqueue_active(&wakeup_count_wait_queue))
> +	if (!inpr && waitqueue_active(&wakeup_count_wait_queue)) {
>  		wake_up(&wakeup_count_wait_queue);
> +		queue_up_suspend_work();
> +	}
>  }
> 
>  /**
> @@ -654,29 +656,33 @@ bool pm_wakeup_pending(void)
>  /**
>   * pm_get_wakeup_count - Read the number of registered wakeup events.
>   * @count: Address to store the value at.
> + * @block: Whether or not to block.
>   *
> - * Store the number of registered wakeup events at the address in @count.  Block
> - * if the current number of wakeup events being processed is nonzero.
> + * Store the number of registered wakeup events at the address in @count.  If
> + * @block is set, block until the current number of wakeup events being
> + * processed is zero.
>   *
> - * Return 'false' if the wait for the number of wakeup events being processed to
> - * drop down to zero has been interrupted by a signal (and the current number
> - * of wakeup events being processed is still nonzero).  Otherwise return 'true'.
> + * Return 'false' if the current number of wakeup events being processed is
> + * nonzero.  Otherwise return 'true'.
>   */
> -bool pm_get_wakeup_count(unsigned int *count)
> +bool pm_get_wakeup_count(unsigned int *count, bool block)
>  {
>  	unsigned int cnt, inpr;
> -	DEFINE_WAIT(wait);
> 
> -	for (;;) {
> -		prepare_to_wait(&wakeup_count_wait_queue, &wait,
> -				TASK_INTERRUPTIBLE);
> -		split_counters(&cnt, &inpr);
> -		if (inpr == 0 || signal_pending(current))
> -			break;
> +	if (block) {
> +		DEFINE_WAIT(wait);
> 
> -		schedule();
> +		for (;;) {
> +			prepare_to_wait(&wakeup_count_wait_queue, &wait,
> +					TASK_INTERRUPTIBLE);
> +			split_counters(&cnt, &inpr);
> +			if (inpr == 0 || signal_pending(current))
> +				break;
> +
> +			schedule();
> +		}
> +		finish_wait(&wakeup_count_wait_queue, &wait);
>  	}
> -	finish_wait(&wakeup_count_wait_queue, &wait);
> 
>  	split_counters(&cnt, &inpr);
>  	*count = cnt;
> Index: linux/Documentation/ABI/testing/sysfs-power
> ===================================================================
> --- linux.orig/Documentation/ABI/testing/sysfs-power
> +++ linux/Documentation/ABI/testing/sysfs-power
> @@ -172,3 +172,20 @@ Description:
> 
>  		Reading from this file will display the current value, which is
>  		set to 1 MB by default.
> +
> +What:		/sys/power/autosleep
> +Date:		February 2012
> +Contact:	Rafael J. Wysocki <rjw@...k.pl>
> +Description:
> +		The /sys/power/autosleep file can be written one of the strings
> +		returned by reads from /sys/power/state.  If that happens, a
> +		work item attempting to trigger a transition of the system to
> +		the sleep state represented by that string is queued up.  This
> +		attempt will only succeed if there are no active wakeup sources
> +		in the system at that time.  After evey execution, regardless
> +		of whether or not the attempt to put the system to sleep has
> +		succeeded, the work item requeues itself until user space
> +		writes "off" to /sys/power/autosleep.
> +
> +		Reading from this file causes the last string successfully
> +		written to it to be displayed.
> 

 

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