PM / Sleep: Implement opportunistic sleep, v2
Rafael J. Wysocki [Sun, 29 Apr 2012 20:53:22 +0000 (22:53 +0200)]
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>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NeilBrown <neilb@suse.de>

Documentation/ABI/testing/sysfs-power
drivers/base/power/wakeup.c
include/linux/suspend.h
kernel/power/Kconfig
kernel/power/Makefile
kernel/power/autosleep.c [new file with mode: 0644]
kernel/power/main.c
kernel/power/power.h

index b464d12..237c735 100644 (file)
@@ -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:          April 2012
+Contact:       Rafael J. Wysocki <rjw@sisk.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 every 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 returned.
index d397ddf..554efa6 100644 (file)
@@ -668,29 +668,33 @@ 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 ac1c114..76b7ec7 100644 (file)
@@ -356,7 +356,7 @@ extern int unregister_pm_notifier(struct notifier_block *nb);
 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(void) {}
 
 #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 c09bbc9..f5dc800 100644 (file)
@@ -111,6 +111,14 @@ 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 c0708ae..010b2f7 100644 (file)
@@ -9,6 +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_SUSPEND_TIME)     += suspend_time.o
+obj-$(CONFIG_PM_AUTOSLEEP)     += autosleep.o
 
 obj-$(CONFIG_MAGIC_SYSRQ)      += poweroff.o
diff --git a/kernel/power/autosleep.c b/kernel/power/autosleep.c
new file mode 100644 (file)
index 0000000..42348e3
--- /dev/null
@@ -0,0 +1,123 @@
+/*
+ * 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;
+/*
+ * Note: it is only safe to mutex_lock(&autosleep_lock) if a wakeup_source
+ * is active, otherwise a deadlock with try_to_suspend() is possible.
+ * Alternatively mutex_lock_interruptible() can be used.  This will then fail
+ * if an auto_sleep cycle tries to freeze processes.
+ */
+static DEFINE_MUTEX(autosleep_lock);
+static struct wakeup_source *autosleep_ws;
+
+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);
+
+       mutex_unlock(&autosleep_lock);
+
+       if (!pm_get_wakeup_count(&final_count, false))
+               goto out;
+
+       /*
+        * If the wakeup occured for an unknown reason, wait to prevent the
+        * system from trying to suspend and waking up in a tight loop.
+        */
+       if (final_count == initial_count)
+               schedule_timeout_uninterruptible(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_lock(void)
+{
+       return mutex_lock_interruptible(&autosleep_lock);
+}
+
+void pm_autosleep_unlock(void)
+{
+       mutex_unlock(&autosleep_lock);
+}
+
+int pm_autosleep_set_state(suspend_state_t state)
+{
+
+#ifndef CONFIG_HIBERNATION
+       if (state >= PM_SUSPEND_MAX)
+               return -EINVAL;
+#endif
+
+       __pm_stay_awake(autosleep_ws);
+
+       mutex_lock(&autosleep_lock);
+
+       autosleep_state = state;
+
+       __pm_relax(autosleep_ws);
+
+       if (state > PM_SUSPEND_ON)
+               queue_up_suspend_work();
+
+       mutex_unlock(&autosleep_lock);
+       return 0;
+}
+
+int __init pm_autosleep_init(void)
+{
+       autosleep_ws = wakeup_source_register("autosleep");
+       if (!autosleep_ws)
+               return -ENOMEM;
+
+       autosleep_wq = alloc_ordered_workqueue("autosleep", 0);
+       if (autosleep_wq)
+               return 0;
+
+       wakeup_source_unregister(autosleep_ws);
+       return -ENOMEM;
+}
index 1c12581..ba6a564 100644 (file)
@@ -269,8 +269,7 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
        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 +277,48 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
 #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;
+
+       error = pm_autosleep_lock();
+       if (error)
+               return error;
+
+       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_MAX)
+               error = hibernate();
+       else
+               error = -EINVAL;
+
+ out:
+       pm_autosleep_unlock();
        return error ? error : n;
 }
 
@@ -339,7 +359,8 @@ static ssize_t wakeup_count_show(struct kobject *kobj,
 {
        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 +368,69 @@ static ssize_t wakeup_count_store(struct kobject *kobj,
                                const char *buf, size_t n)
 {
        unsigned int val;
+       int error;
+
+       error = pm_autosleep_lock();
+       if (error)
+               return error;
 
+       if (pm_autosleep_state() > PM_SUSPEND_ON) {
+               error = -EBUSY;
+               goto out;
+       }
+
+       error = -EINVAL;
        if (sscanf(buf, "%u", &val) == 1) {
                if (pm_save_wakeup_count(val))
-                       return n;
+                       error = 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 +484,9 @@ 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 +522,10 @@ 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 98f3622..4cf80fa 100644 (file)
@@ -264,3 +264,21 @@ static inline void suspend_thaw_processes(void)
 {
 }
 #endif
+
+#ifdef CONFIG_PM_AUTOSLEEP
+
+/* kernel/power/autosleep.c */
+extern int pm_autosleep_init(void);
+extern int 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 int pm_autosleep_lock(void) { return 0; }
+static inline void pm_autosleep_unlock(void) {}
+static inline suspend_state_t pm_autosleep_state(void) { return PM_SUSPEND_ON; }
+
+#endif /* !CONFIG_PM_AUTOSLEEP */