Message-ID: <20100504051256.GC3043@thegnar.org>
Date:	Mon, 3 May 2010 22:12:56 -0700
From:	mark gross <640e9920@...il.com>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>, linux-doc@...r.kernel.org,
	Oleg Nesterov <oleg@...hat.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Tejun Heo <tj@...nel.org>, Magnus Damm <damm@...l.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

On Fri, Apr 30, 2010 at 03:36:54PM -0700, Arve Hjønnevåg wrote:
> Adds /sys/power/policy that selects the behaviour of /sys/power/state.
> After setting the policy to opportunistic, writes to /sys/power/state
> become non-blocking requests that specify which suspend state to enter
> when no suspend blockers are active. A special state, "on", stops the
> process by activating the "main" suspend blocker.
> 
> Signed-off-by: Arve Hjønnevåg <arve@...roid.com>
> ---
>  Documentation/power/opportunistic-suspend.txt |  119 +++++++++++
>  include/linux/suspend_blocker.h               |   64 ++++++
>  kernel/power/Kconfig                          |   16 ++
>  kernel/power/Makefile                         |    1 +
>  kernel/power/main.c                           |   92 ++++++++-
>  kernel/power/power.h                          |    9 +
>  kernel/power/suspend.c                        |    4 +-
>  kernel/power/suspend_blocker.c                |  261 +++++++++++++++++++++++++
>  8 files changed, 559 insertions(+), 7 deletions(-)
>  create mode 100644 Documentation/power/opportunistic-suspend.txt
>  create mode 100755 include/linux/suspend_blocker.h
>  create mode 100644 kernel/power/suspend_blocker.c
> 
> diff --git a/Documentation/power/opportunistic-suspend.txt b/Documentation/power/opportunistic-suspend.txt
> new file mode 100644
> index 0000000..3d060e8
> --- /dev/null
> +++ b/Documentation/power/opportunistic-suspend.txt
> @@ -0,0 +1,119 @@
> +Opportunistic Suspend
> +=====================
> +
> +Opportunistic suspend is a feature allowing the system to be suspended (ie. put
> +into one of the available sleep states) automatically whenever it is regarded
> +as idle.  The suspend blockers framework described below is used to determine
> +when that happens.
> +
> +The /sys/power/policy sysfs attribute is used to switch the system between the
> +opportunistic and "forced" suspend behavior, where in the latter case the
> +system is only suspended if a specific value, corresponding to one of the
> +available system sleep states, is written into /sys/power/state.  However, in
> +the former, opportunistic, case the system is put into the sleep state
> +corresponding to the value written to /sys/power/state whenever there are no
> +active suspend blockers. The default policy is "forced". Also, suspend blockers
> +do not affect sleep states entered from idle.
> +
> +When the policy is "opportunisic", there is a special value, "on", that can be
> +written to /sys/power/state. This will block the automatic sleep request, as if
> +a suspend blocker was used by a device driver. This way the opportunistic
> +suspend may be blocked by user space whithout switching back to the "forced"
> +mode.

You know things would be so much easier if the policy was a one-shot
styled thing.  i.e. when enabled it does what it does, but upon resume
the policy must be re-enabled by user mode to get the opportunistic
behavior.  That way we don't need to grab the suspend blocker from the
wake up irq handler all the way up to user mode as the example below
calls out.  I suppose doing this would put a burden on the user mode code
to keep track of if it has no pending blockers registered after a wake
up from the suspend.  but that seems nicer to me than sprinkling
overlapping blocker critical sections from the mettle up to user mode.

Please consider making the policy a one shot API that needs to be
re-enabled after resume by user mode.  That would remove my issue with
the design.

--mgross

> +
> +A suspend blocker is an object used to inform the PM subsystem when the system
> +can or cannot be suspended in the "opportunistic" mode (the "forced" mode
> +ignores suspend blockers).  To use it, a device driver creates a struct
> +suspend_blocker that must be initialized with suspend_blocker_init(). Before
> +freeing the suspend_blocker structure or its name, suspend_blocker_destroy()
> +must be called on it.
> +
> +A suspend blocker is activated using suspend_block(), which prevents the PM
> +subsystem from putting the system into the requested sleep state in the
> +"opportunistic" mode until the suspend blocker is deactivated with
> +suspend_unblock(). Multiple suspend blockers may be active simultaneously, and
> +the system will not suspend as long as at least one of them is active.
> +
> +If opportunistic suspend is already in progress when suspend_block() is called,
> +it will abort the suspend, unless suspend_ops->enter has already been
> +executed. If suspend is aborted this way, the system is usually not fully
> +operational at that point. The suspend callbacks of some drivers may still be
> +running and it usually takes time to restore the system to the fully operational
> +state.
> +
> +Here's an example showing how a cell phone or other embedded system can handle
> +keystrokes (or other input events) in the presence of suspend blockers. Use
> +set_irq_wake or a platform specific api to make sure the keypad interrupt wakes
> +up the cpu. Once the keypad driver has resumed, the sequence of events can look
> +like this:
> +
> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> +- The keypad-scan code detects a key change and reports it to the input-event
> +  driver.
> +- The input-event driver sees the key change, enqueues an event, and calls
> +  suspend_block on the input-event-queue suspend_blocker.
> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> +  on the keypad-scan suspend_blocker.
> +- The user-space input-event thread returns from select/poll, calls
> +  suspend_block on the process-input-events suspend_blocker and then calls read
> +  on the input-event device.
> +- The input-event driver dequeues the key-event and, since the queue is now
> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> +- The user-space input-event thread returns from read. If it determines that
> +  the key should be ignored, it calls suspend_unblock on the
> +  process_input_events suspend_blocker and then calls select or poll. The
> +  system will automatically suspend again, since now no suspend blockers are
> +  active.
> +
> +If the key that was pressed instead should preform a simple action (for example,
> +adjusting the volume), this action can be performed right before calling
> +suspend_unblock on the process_input_events suspend_blocker. However, if the key
> +triggers a longer-running action, that action needs its own suspend_blocker and
> +suspend_block must be called on that suspend blocker before calling
> +suspend_unblock on the process_input_events suspend_blocker.
> +
> +                 Key pressed   Key released
> +                     |             |
> +keypad-scan          ++++++++++++++++++
> +input-event-queue        +++          +++
> +process-input-events       +++          +++
> +
> +
> +Driver API
> +==========
> +
> +A driver can use the suspend block api by adding a suspend_blocker variable to
> +its state and calling suspend_blocker_init. For instance:
> +struct state {
> +	struct suspend_blocker suspend_blocker;
> +}
> +
> +init() {
> +	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
> +}
> +
> +Before freeing the memory, suspend_blocker_destroy must be called:
> +
> +uninit() {
> +	suspend_blocker_destroy(&state->suspend_blocker);
> +}
> +
> +When the driver determines that it needs to run (usually in an interrupt
> +handler) it calls suspend_block:
> +	suspend_block(&state->suspend_blocker);
> +
> +When it no longer needs to run it calls suspend_unblock:
> +	suspend_unblock(&state->suspend_blocker);
> +
> +Calling suspend_block when the suspend blocker is active or suspend_unblock when
> +it is not active has no effect (i.e., these functions don't nest). This allows
> +drivers to update their state and call suspend suspend_block or suspend_unblock
> +based on the result.
> +For instance:
> +
> +if (list_empty(&state->pending_work))
> +	suspend_unblock(&state->suspend_blocker);
> +else
> +	suspend_block(&state->suspend_blocker);
> +
> diff --git a/include/linux/suspend_blocker.h b/include/linux/suspend_blocker.h
> new file mode 100755
> index 0000000..f9928cc
> --- /dev/null
> +++ b/include/linux/suspend_blocker.h
> @@ -0,0 +1,64 @@
> +/* include/linux/suspend_blocker.h
> + *
> + * Copyright (C) 2007-2009 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef _LINUX_SUSPEND_BLOCKER_H
> +#define _LINUX_SUSPEND_BLOCKER_H
> +
> +#include <linux/list.h>
> +
> +/**
> + * struct suspend_blocker - the basic suspend_blocker structure
> + * @link:	List entry for active or inactive list.
> + * @flags:	Tracks initialized and active state.
> + * @name:	Name used for debugging.
> + *
> + * When a suspend_blocker is active it prevents the system from entering
> + * opportunistic suspend.
> + *
> + * The suspend_blocker structure must be initialized by suspend_blocker_init()
> + */
> +
> +struct suspend_blocker {
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +	struct list_head    link;
> +	int                 flags;
> +	const char         *name;
> +#endif
> +};
> +
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
> +void suspend_block(struct suspend_blocker *blocker);
> +void suspend_unblock(struct suspend_blocker *blocker);
> +bool suspend_blocker_is_active(struct suspend_blocker *blocker);
> +bool suspend_is_blocked(void);
> +
> +#else
> +
> +static inline void suspend_blocker_init(struct suspend_blocker *blocker,
> +					const char *name) {}
> +static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
> +static inline void suspend_block(struct suspend_blocker *blocker) {}
> +static inline void suspend_unblock(struct suspend_blocker *blocker) {}
> +static inline bool suspend_blocker_is_active(struct suspend_blocker *bl)
> +								{ return 0; }
> +static inline bool suspend_is_blocked(void) { return 0; }
> +
> +#endif
> +
> +#endif
> +
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 5c36ea9..55a06a1 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -130,6 +130,22 @@ config SUSPEND_FREEZER
>  
>  	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
>  
> +config OPPORTUNISTIC_SUSPEND
> +	bool "Suspend blockers"
> +	depends on PM_SLEEP
> +	select RTC_LIB
> +	default n
> +	---help---
> +	  Opportunistic sleep support.  Allows the system to be put into a sleep
> +	  state opportunistically, if it doesn't do any useful work at the
> +	  moment. The PM subsystem is switched into this mode of operation by
> +	  writing "opportunistic" into /sys/power/policy, while writing
> +	  "forced" to this file turns the opportunistic suspend feature off.
> +	  In the "opportunistic" mode suspend blockers are used to determine
> +	  when to suspend the system and the value written to /sys/power/state
> +	  determines the sleep state the system will be put into when there are
> +	  no active suspend blockers.
> +
>  config HIBERNATION_NVS
>  	bool
>  
> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
> index 4319181..ee5276d 100644
> --- a/kernel/power/Makefile
> +++ b/kernel/power/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_PM)		+= main.o
>  obj-$(CONFIG_PM_SLEEP)		+= console.o
>  obj-$(CONFIG_FREEZER)		+= process.o
>  obj-$(CONFIG_SUSPEND)		+= suspend.o
> +obj-$(CONFIG_OPPORTUNISTIC_SUSPEND)	+= suspend_blocker.o
>  obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
>  obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o
>  obj-$(CONFIG_HIBERNATION_NVS)	+= hibernate_nvs.o
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index b58800b..030ecdc 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -12,6 +12,7 @@
>  #include <linux/string.h>
>  #include <linux/resume-trace.h>
>  #include <linux/workqueue.h>
> +#include <linux/suspend_blocker.h>
>  
>  #include "power.h"
>  
> @@ -20,6 +21,27 @@ DEFINE_MUTEX(pm_mutex);
>  unsigned int pm_flags;
>  EXPORT_SYMBOL(pm_flags);
>  
> +struct policy {
> +	const char *name;
> +	bool (*valid_state)(suspend_state_t state);
> +	int (*set_state)(suspend_state_t state);
> +};
> +static struct policy policies[] = {
> +	{
> +		.name		= "forced",
> +		.valid_state	= valid_state,
> +		.set_state	= enter_state,
> +	},
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +	{
> +		.name		= "opportunistic",
> +		.valid_state	= request_suspend_valid_state,
> +		.set_state	= request_suspend_state,
> +	},
> +#endif
> +};
> +static int policy;
> +
>  #ifdef CONFIG_PM_SLEEP
>  
>  /* Routines for PM-transition notifications */
> @@ -146,6 +168,12 @@ struct kobject *power_kobj;
>   *
>   *	store() accepts one of those strings, translates it into the 
>   *	proper enumerated value, and initiates a suspend transition.
> + *
> + *	If policy is set to opportunistic, store() does not block until the
> + *	system resumes, and it will try to re-enter the state until another
> + *	state is requested. Suspend blockers are respected and the requested
> + *	state will only be entered when no suspend blockers are active.
> + *	Write "on" to cancel.
>   */
>  static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
>  			  char *buf)
> @@ -155,12 +183,13 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
>  	int i;
>  
>  	for (i = 0; i < PM_SUSPEND_MAX; i++) {
> -		if (pm_states[i] && valid_state(i))
> +		if (pm_states[i] && policies[policy].valid_state(i))
>  			s += sprintf(s,"%s ", pm_states[i]);
>  	}
>  #endif
>  #ifdef CONFIG_HIBERNATION
> -	s += sprintf(s, "%s\n", "disk");
> +	if (!policy)
> +		s += sprintf(s, "%s\n", "disk");
>  #else
>  	if (s != buf)
>  		/* convert the last space to a newline */
> @@ -173,7 +202,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  			   const char *buf, size_t n)
>  {
>  #ifdef CONFIG_SUSPEND
> -	suspend_state_t state = PM_SUSPEND_STANDBY;
> +	suspend_state_t state = PM_SUSPEND_ON;
>  	const char * const *s;
>  #endif
>  	char *p;
> @@ -184,7 +213,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	len = p ? p - buf : n;
>  
>  	/* First, check if we are requested to hibernate */
> -	if (len == 4 && !strncmp(buf, "disk", len)) {
> +	if (len == 4 && !strncmp(buf, "disk", len) && !policy) {
>  		error = hibernate();
>    goto Exit;
>  	}
> @@ -195,7 +224,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  			break;
>  	}
>  	if (state < PM_SUSPEND_MAX && *s)
> -		error = enter_state(state);
> +		error = policies[policy].set_state(state);
>  #endif
>  
>   Exit:
> @@ -204,6 +233,55 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  
>  power_attr(state);
>  
> +/**
> + *	policy - set policy for state
> + */
> +
> +static ssize_t policy_show(struct kobject *kobj,
> +			   struct kobj_attribute *attr, char *buf)
> +{
> +	char *s = buf;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(policies); i++) {
> +		if (i == policy)
> +			s += sprintf(s, "[%s] ", policies[i].name);
> +		else
> +			s += sprintf(s, "%s ", policies[i].name);
> +	}
> +	if (s != buf)
> +		/* convert the last space to a newline */
> +		*(s-1) = '\n';
> +	return (s - buf);
> +}
> +
> +static ssize_t policy_store(struct kobject *kobj,
> +			    struct kobj_attribute *attr,
> +			    const char *buf, size_t n)
> +{
> +	const char *s;
> +	char *p;
> +	int len;
> +	int i;
> +
> +	p = memchr(buf, '\n', n);
> +	len = p ? p - buf : n;
> +
> +	for (i = 0; i < ARRAY_SIZE(policies); i++) {
> +		s = policies[i].name;
> +		if (s && len == strlen(s) && !strncmp(buf, s, len)) {
> +			mutex_lock(&pm_mutex);
> +			policies[policy].set_state(PM_SUSPEND_ON);
> +			policy = i;
> +			mutex_unlock(&pm_mutex);
> +			return n;
> +		}
> +	}
> +	return -EINVAL;
> +}
> +
> +power_attr(policy);
> +
>  #ifdef CONFIG_PM_TRACE
>  int pm_trace_enabled;
>  
> @@ -231,6 +309,7 @@ power_attr(pm_trace);
>  
>  static struct attribute * g[] = {
>  	&state_attr.attr,
> +	&policy_attr.attr,
>  #ifdef CONFIG_PM_TRACE
>  	&pm_trace_attr.attr,
>  #endif
> @@ -247,7 +326,7 @@ static struct attribute_group attr_group = {
>  	.attrs = g,
>  };
>  
> -#ifdef CONFIG_PM_RUNTIME
> +#if defined(CONFIG_PM_RUNTIME) || defined(CONFIG_OPPORTUNISTIC_SUSPEND)
>  struct workqueue_struct *pm_wq;
>  EXPORT_SYMBOL_GPL(pm_wq);
>  
> @@ -266,6 +345,7 @@ static int __init pm_init(void)
>  	int error = pm_start_workqueue();
>  	if (error)
>  		return error;
> +	suspend_block_init();
>  	power_kobj = kobject_create_and_add("power", NULL);
>  	if (!power_kobj)
>  		return -ENOMEM;
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 46c5a26..67d10fd 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -236,3 +236,12 @@ static inline void suspend_thaw_processes(void)
>  {
>  }
>  #endif
> +
> +/* kernel/power/suspend_block.c */
> +extern int request_suspend_state(suspend_state_t state);
> +extern bool request_suspend_valid_state(suspend_state_t state);
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +extern void __init suspend_block_init(void);
> +#else
> +static inline void suspend_block_init(void) {}
> +#endif
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 56e7dbb..dc42006 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -16,10 +16,12 @@
>  #include <linux/cpu.h>
>  #include <linux/syscalls.h>
>  #include <linux/gfp.h>
> +#include <linux/suspend_blocker.h>
>  
>  #include "power.h"
>  
>  const char *const pm_states[PM_SUSPEND_MAX] = {
> +	[PM_SUSPEND_ON]		= "on",
>  	[PM_SUSPEND_STANDBY]	= "standby",
>  	[PM_SUSPEND_MEM]	= "mem",
>  };
> @@ -157,7 +159,7 @@ static int suspend_enter(suspend_state_t state)
>  
>  	error = sysdev_suspend(PMSG_SUSPEND);
>  	if (!error) {
> -		if (!suspend_test(TEST_CORE))
> +		if (!suspend_is_blocked() && !suspend_test(TEST_CORE))
>  			error = suspend_ops->enter(state);
>  		sysdev_resume();
>  	}
> diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
> new file mode 100644
> index 0000000..2c58b21
> --- /dev/null
> +++ b/kernel/power/suspend_blocker.c
> @@ -0,0 +1,261 @@
> +/* kernel/power/suspend_blocker.c
> + *
> + * Copyright (C) 2005-2010 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/rtc.h>
> +#include <linux/suspend.h>
> +#include <linux/suspend_blocker.h>
> +#include "power.h"
> +
> +extern struct workqueue_struct *pm_wq;
> +
> +enum {
> +	DEBUG_EXIT_SUSPEND = 1U << 0,
> +	DEBUG_WAKEUP = 1U << 1,
> +	DEBUG_USER_STATE = 1U << 2,
> +	DEBUG_SUSPEND = 1U << 3,
> +	DEBUG_SUSPEND_BLOCKER = 1U << 4,
> +};
> +static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
> +
> +#define SB_INITIALIZED            (1U << 8)
> +#define SB_ACTIVE                 (1U << 9)
> +
> +static DEFINE_SPINLOCK(list_lock);
> +static DEFINE_SPINLOCK(state_lock);
> +static LIST_HEAD(inactive_blockers);
> +static LIST_HEAD(active_blockers);
> +static int current_event_num;
> +struct suspend_blocker main_suspend_blocker;
> +static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
> +static bool enable_suspend_blockers;
> +
> +#define pr_info_time(fmt, args...) \
> +	do { \
> +		struct timespec ts; \
> +		struct rtc_time tm; \
> +		getnstimeofday(&ts); \
> +		rtc_time_to_tm(ts.tv_sec, &tm); \
> +		pr_info(fmt "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n" , \
> +			args, \
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, \
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
> +	} while (0);
> +
> +static void print_active_blockers_locked(void)
> +{
> +	struct suspend_blocker *blocker;
> +
> +	list_for_each_entry(blocker, &active_blockers, link)
> +		pr_info("active suspend blocker %s\n", blocker->name);
> +}
> +
> +/**
> + * suspend_is_blocked() - Check if suspend should be blocked
> + *
> + * suspend_is_blocked can be used by generic power management code to abort
> + * suspend.
> + *
> + * To preserve backward compatibility suspend_is_blocked returns 0 unless it
> + * is called during suspend initiated from the suspend_block code.
> + */
> +bool suspend_is_blocked(void)
> +{
> +	if (!enable_suspend_blockers)
> +		return 0;
> +	return !list_empty(&active_blockers);
> +}
> +
> +static void suspend_worker(struct work_struct *work)
> +{
> +	int ret;
> +	int entry_event_num;
> +
> +	enable_suspend_blockers = true;
> +	while (!suspend_is_blocked()) {
> +		entry_event_num = current_event_num;
> +
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: enter suspend\n");
> +
> +		ret = pm_suspend(requested_suspend_state);
> +
> +		if (debug_mask & DEBUG_EXIT_SUSPEND)
> +			pr_info_time("suspend: exit suspend, ret = %d ", ret);
> +
> +		if (current_event_num == entry_event_num)
> +			pr_info("suspend: pm_suspend returned with no event\n");
> +	}
> +	enable_suspend_blockers = false;
> +}
> +static DECLARE_WORK(suspend_work, suspend_worker);
> +
> +/**
> + * suspend_blocker_init() - Initialize a suspend blocker
> + * @blocker:	The suspend blocker to initialize.
> + * @name:	The name of the suspend blocker to show in debug messages.
> + *
> + * The suspend blocker struct and name must not be freed before calling
> + * suspend_blocker_destroy.
> + */
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
> +{
> +	unsigned long irqflags = 0;
> +
> +	WARN_ON(!name);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_init name=%s\n", name);
> +
> +	blocker->name = name;
> +	blocker->flags = SB_INITIALIZED;
> +	INIT_LIST_HEAD(&blocker->link);
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	list_add(&blocker->link, &inactive_blockers);
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_blocker_init);
> +
> +/**
> + * suspend_blocker_destroy() - Destroy a suspend blocker
> + * @blocker:	The suspend blocker to destroy.
> + */
> +void suspend_blocker_destroy(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	blocker->flags &= ~SB_INITIALIZED;
> +	list_del(&blocker->link);
> +	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
> +		queue_work(pm_wq, &suspend_work);
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_blocker_destroy);
> +
> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_block: %s\n", blocker->name);
> +
> +	blocker->flags |= SB_ACTIVE;
> +	list_move(&blocker->link, &active_blockers);
> +	current_event_num++;
> +
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_block);
> +
> +/**
> + * suspend_unblock() - Unblock suspend
> + * @blocker:	The suspend blocker to unblock.
> + *
> + * If no other suspend blockers block suspend, the system will suspend.
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_unblock(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_unblock: %s\n", blocker->name);
> +
> +	list_move(&blocker->link, &inactive_blockers);
> +
> +	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
> +		queue_work(pm_wq, &suspend_work);
> +	blocker->flags &= ~(SB_ACTIVE);
> +	if (blocker == &main_suspend_blocker) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			print_active_blockers_locked();
> +	}
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_unblock);
> +
> +/**
> + * suspend_blocker_is_active() - Test if a suspend blocker is blocking suspend
> + * @blocker:	The suspend blocker to check.
> + *
> + * Returns true if the suspend_blocker is currently active.
> + */
> +bool suspend_blocker_is_active(struct suspend_blocker *blocker)
> +{
> +	WARN_ON(!(blocker->flags & SB_INITIALIZED));
> +
> +	return !!(blocker->flags & SB_ACTIVE);
> +}
> +EXPORT_SYMBOL(suspend_blocker_is_active);
> +
> +bool request_suspend_valid_state(suspend_state_t state)
> +{
> +	return (state == PM_SUSPEND_ON) || valid_state(state);
> +}
> +
> +int request_suspend_state(suspend_state_t state)
> +{
> +	unsigned long irqflags;
> +
> +	if (!request_suspend_valid_state(state))
> +		return -ENODEV;
> +
> +	spin_lock_irqsave(&state_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_USER_STATE)
> +		pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
> +			     state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> +			     requested_suspend_state, state,
> +			     ktime_to_ns(ktime_get()));
> +
> +	requested_suspend_state = state;
> +	if (state == PM_SUSPEND_ON)
> +		suspend_block(&main_suspend_blocker);
> +	else
> +		suspend_unblock(&main_suspend_blocker);
> +	spin_unlock_irqrestore(&state_lock, irqflags);
> +	return 0;
> +}
> +
> +void __init suspend_block_init(void)
> +{
> +	suspend_blocker_init(&main_suspend_blocker, "main");
> +	suspend_block(&main_suspend_blocker);
> +}
> -- 
> 1.6.5.1
> 
> _______________________________________________
> linux-pm mailing list
> linux-pm@...ts.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/linux-pm
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