Re: [RFC][PATCH 5/7] PM / Sleep: Implement opportunistic sleep

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, February 22, 2012, Srivatsa S. Bhat wrote:
> On 02/22/2012 05:05 AM, Rafael J. Wysocki wrote:
> 
> > From: Rafael J. Wysocki <rjw@sisk.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@sisk.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@sisk.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.

Both pm_suspend() and hibernate() have appropriate static inline definitions
for !CONFIG_SUSPEND and !CONFIG_HIBERNATION (in suspend.h), as far as I can say.

Thanks,
Rafael