[RFC][PATCH 8/8] PM / Sleep: Add user space interface for manipulating wakeup sources

From: Rafael J. Wysocki
Date: Mon Feb 06 2012 - 20:06:38 EST


From: Rafael J. Wysocki <rjw@xxxxxxx>

Android allows user space to manipulate wakelocks using two
sysfs file located in /sys/power/, wake_lock and wake_unlock.
Writing a wakelock name and optionally a timeout to the wake_lock
file causes the wakelock whose name was written to be acquired (it
is created before is necessary), optionally with the given timeout.
Writing the name of a wakelock to wake_unlock causes that wakelock
to be released.

Implement an analogous interface for user space using wakeup sources.
Add the /sys/power/wake_lock and /sys/power/wake_unlock files
allowing user space to create, activate and deactivate wakeup
sources, such that writing a name and optionally a timeout to
wake_lock causes the wakeup source of that name to be activated,
optionally with the given timeout. If that wakeup source doesn't
exist, it will be created and then activated. Writing a name to
wake_unlock causes the wakeup source of that name, if there is one,
to be deactivated. Wakeup sources created with the help of
wake_lock that haven't been used for more than 5 minutes are garbage
collected and destroyed. Moreover, there can be only WL_NUMBER_LIMIT
wakeup sources created with the help of wake_lock present at a time.

The data type used to track wakeup sources created by user space is
called "struct wakelock" to indicate the origins of this feature.

---
drivers/base/power/wakeup.c | 1
kernel/power/Kconfig | 8 +
kernel/power/Makefile | 1
kernel/power/main.c | 41 ++++++++
kernel/power/power.h | 9 +
kernel/power/wakelock.c | 218 ++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 278 insertions(+)

Index: linux/kernel/power/main.c
===================================================================
--- linux.orig/kernel/power/main.c
+++ linux/kernel/power/main.c
@@ -415,6 +415,43 @@ static ssize_t autosleep_store(struct ko

power_attr(autosleep);
#endif /* CONFIG_PM_AUTOSLEEP */
+
+#ifdef CONFIG_PM_WAKELOCKS
+static ssize_t wake_lock_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return pm_show_wakelocks(buf, true);
+}
+
+static ssize_t wake_lock_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ int error = pm_wake_lock(buf);
+ return error ? error : n;
+}
+
+power_attr(wake_lock);
+
+static ssize_t wake_unlock_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return pm_show_wakelocks(buf, false);
+}
+
+static ssize_t wake_unlock_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ int error = pm_wake_unlock(buf);
+ return error ? error : n;
+}
+
+power_attr(wake_unlock);
+
+#endif /* CONFIG_PM_WAKELOCKS */
#endif /* CONFIG_PM_SLEEP */

#ifdef CONFIG_PM_TRACE
@@ -471,6 +508,10 @@ static struct attribute * g[] = {
#ifdef CONFIG_PM_AUTOSLEEP
&autosleep_attr.attr,
#endif
+#ifdef CONFIG_PM_WAKELOCKS
+ &wake_lock_attr.attr,
+ &wake_unlock_attr.attr,
+#endif
#ifdef CONFIG_PM_DEBUG
&pm_test_attr.attr,
#endif
Index: linux/kernel/power/power.h
===================================================================
--- linux.orig/kernel/power/power.h
+++ linux/kernel/power/power.h
@@ -287,3 +287,12 @@ static inline void pm_autosleep_unlock(v
static inline suspend_state_t pm_autosleep_state(void) { return PM_SUSPEND_ON; }

#endif /* !CONFIG_PM_AUTOSLEEP */
+
+#ifdef CONFIG_PM_WAKELOCKS
+
+/* kernel/power/wakelock.c */
+extern ssize_t pm_show_wakelocks(char *buf, bool show_active);
+extern int pm_wake_lock(const char *buf);
+extern int pm_wake_unlock(const char *buf);
+
+#endif /* !CONFIG_PM_WAKELOCKS */
Index: linux/kernel/power/Kconfig
===================================================================
--- linux.orig/kernel/power/Kconfig
+++ linux/kernel/power/Kconfig
@@ -111,6 +111,14 @@ config PM_AUTOSLEEP
Allow the kernel to trigger a system transition into a global sleep
state automatically whenever there are no active wakeup sources.

+config PM_WAKELOCKS
+ bool "User space wakeup sources interface"
+ depends on PM_SLEEP
+ default n
+ ---help---
+ Allow user space to create, activate and deactivate wakeup source
+ objects with the help of a sysfs-based interface.
+
config PM_RUNTIME
bool "Run-time PM core functionality"
depends on !IA64_HP_SIM
Index: linux/kernel/power/wakelock.c
===================================================================
--- /dev/null
+++ linux/kernel/power/wakelock.c
@@ -0,0 +1,218 @@
+/*
+ * kernel/power/wakelock.c
+ *
+ * User space wakeup sources support.
+ *
+ * Copyright (C) 2012 Rafael J. Wysocki <rjw@xxxxxxx>
+ *
+ * This code is based on the analogous interface allowing user space to
+ * manipulate wakelocks on Android.
+ */
+
+#include <linux/ctype.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/list.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+
+#define WL_NUMBER_LIMIT 100
+#define WL_GC_COUNT_MAX 100
+#define WL_GC_TIME_SEC 300
+
+static DEFINE_MUTEX(wakelocks_lock);
+
+struct wakelock {
+ char *name;
+ struct rb_node node;
+ struct wakeup_source ws;
+ struct list_head lru;
+};
+
+static struct rb_root wakelocks_tree = RB_ROOT;
+static LIST_HEAD(wakelocks_lru_list);
+static unsigned int number_of_wakelocks;
+static unsigned int wakelocks_gc_count;
+
+ssize_t pm_show_wakelocks(char *buf, bool show_active)
+{
+ struct rb_node *node;
+ struct wakelock *wl;
+ char *str = buf;
+ char *end = buf + PAGE_SIZE;
+
+ mutex_lock(&wakelocks_lock);
+
+ for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
+ bool active;
+
+ wl = rb_entry(node, struct wakelock, node);
+ spin_lock_irq(&wl->ws.lock);
+ active = wl->ws.active;
+ spin_unlock_irq(&wl->ws.lock);
+ if (active == show_active)
+ str += scnprintf(str, end - str, "%s ", wl->name);
+ }
+ str += scnprintf(str, end - str, "\n");
+
+ mutex_unlock(&wakelocks_lock);
+ return (str - buf);
+}
+
+static struct wakelock *wakelock_lookup_add(const char *name, size_t len,
+ bool add_if_not_found)
+{
+ struct rb_node **node = &wakelocks_tree.rb_node;
+ struct rb_node *parent = *node;
+ struct wakelock *wl;
+
+ while (*node) {
+ int diff;
+
+ wl = rb_entry(*node, struct wakelock, node);
+ diff = strncmp(name, wl->name, len);
+ if (diff == 0) {
+ if (wl->name[len])
+ diff = -1;
+ else
+ return wl;
+ }
+ if (diff < 0)
+ node = &(*node)->rb_left;
+ else
+ node = &(*node)->rb_right;
+
+ parent = *node;
+ }
+ if (!add_if_not_found)
+ return ERR_PTR(-EINVAL);
+
+ if (number_of_wakelocks > WL_NUMBER_LIMIT)
+ return ERR_PTR(-ENOSPC);
+
+ /* Not found, we have to add a new one. */
+ wl = kzalloc(sizeof(*wl), GFP_KERNEL);
+ if (!wl)
+ return ERR_PTR(-ENOMEM);
+
+ wl->name = kstrndup(name, len, GFP_KERNEL);
+ if (!wl->name) {
+ kfree(wl);
+ return ERR_PTR(-ENOMEM);
+ }
+ wl->ws.name = wl->name;
+ wakeup_source_add(&wl->ws);
+ rb_link_node(&wl->node, parent, node);
+ rb_insert_color(&wl->node, &wakelocks_tree);
+ list_add(&wl->lru, &wakelocks_lru_list);
+ number_of_wakelocks++;
+ return wl;
+}
+
+int pm_wake_lock(const char *buf)
+{
+ const char *str = buf;
+ struct wakelock *wl;
+ u64 timeout_ns = 0;
+ size_t len;
+ int ret = 0;
+
+ while (*str && !isspace(*str))
+ str++;
+
+ len = str - buf;
+ if (!len)
+ return -EINVAL;
+
+ if (*str && *str != '\n') {
+ /* Find out if there's a valid timeout string appended. */
+ ret = kstrtou64(skip_spaces(str), 10, &timeout_ns);
+ if (ret)
+ return -EINVAL;
+ }
+
+ mutex_lock(&wakelocks_lock);
+
+ wl = wakelock_lookup_add(buf, len, true);
+ if (IS_ERR(wl)) {
+ ret = PTR_ERR(wl);
+ goto out;
+ }
+ if (timeout_ns) {
+ u64 timeout_ms = timeout_ns + NSEC_PER_MSEC - 1;
+
+ do_div(timeout_ms, NSEC_PER_MSEC);
+ __pm_wakeup_event(&wl->ws, timeout_ms);
+ } else {
+ __pm_stay_awake(&wl->ws);
+ }
+
+ list_move(&wl->lru, &wakelocks_lru_list);
+
+ out:
+ mutex_unlock(&wakelocks_lock);
+ return ret;
+}
+
+static void wakelocks_gc(void)
+{
+ struct wakelock *wl, *aux;
+ ktime_t now = ktime_get();
+
+ list_for_each_entry_safe_reverse(wl, aux, &wakelocks_lru_list, lru) {
+ u64 idle_time_ns;
+ bool active;
+
+ spin_lock_irq(&wl->ws.lock);
+ idle_time_ns = ktime_to_ns(ktime_sub(now, wl->ws.last_time));
+ active = wl->ws.active;
+ spin_unlock_irq(&wl->ws.lock);
+
+ if (idle_time_ns < ((u64)WL_GC_TIME_SEC * NSEC_PER_SEC))
+ break;
+
+ if (!active) {
+ wakeup_source_remove(&wl->ws);
+ rb_erase(&wl->node, &wakelocks_tree);
+ list_del(&wl->lru);
+ kfree(wl->name);
+ kfree(wl);
+ number_of_wakelocks--;
+ }
+ }
+ wakelocks_gc_count = 0;
+}
+
+int pm_wake_unlock(const char *buf)
+{
+ struct wakelock *wl;
+ size_t len;
+ int ret = 0;
+
+ len = strlen(buf);
+ if (!len)
+ return -EINVAL;
+
+ if (buf[len-1] == '\n')
+ len--;
+
+ if (!len)
+ return -EINVAL;
+
+ mutex_lock(&wakelocks_lock);
+
+ wl = wakelock_lookup_add(buf, len, false);
+ if (IS_ERR(wl)) {
+ ret = PTR_ERR(wl);
+ goto out;
+ }
+ __pm_relax(&wl->ws);
+ list_move(&wl->lru, &wakelocks_lru_list);
+ if (++wakelocks_gc_count > WL_GC_COUNT_MAX)
+ wakelocks_gc();
+
+ out:
+ mutex_unlock(&wakelocks_lock);
+ return ret;
+}
Index: linux/kernel/power/Makefile
===================================================================
--- linux.orig/kernel/power/Makefile
+++ linux/kernel/power/Makefile
@@ -9,5 +9,6 @@ obj-$(CONFIG_PM_TEST_SUSPEND) += suspend
obj-$(CONFIG_HIBERNATION) += hibernate.o snapshot.o swap.o user.o \
block_io.o
obj-$(CONFIG_PM_AUTOSLEEP) += autosleep.o
+obj-$(CONFIG_PM_WAKELOCKS) += wakelock.o

obj-$(CONFIG_MAGIC_SYSRQ) += poweroff.o
Index: linux/drivers/base/power/wakeup.c
===================================================================
--- linux.orig/drivers/base/power/wakeup.c
+++ linux/drivers/base/power/wakeup.c
@@ -107,6 +107,7 @@ void wakeup_source_add(struct wakeup_sou
spin_lock_init(&ws->lock);
setup_timer(&ws->timer, pm_wakeup_timer_fn, (unsigned long)ws);
ws->active = false;
+ ws->last_time = ktime_get();

spin_lock_irq(&events_lock);
list_add_rcu(&ws->entry, &wakeup_sources);
--
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