wakelock.c

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/*
 * kernel/power/wakelock.c
 *
 * User space wakeup sources support.
 *
 * Copyright (C) 2012 Rafael J. Wysocki <[email protected]>
 *
 * This code is based on the analogous interface allowing user space to
 * manipulate wakelocks on Android.
 */

#include <linux/capability.h>
#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>

static DEFINE_MUTEX(wakelocks_lock);

struct wakelock {
    char            *name;
    struct rb_node      node;
    struct wakeup_source    ws;
#ifdef CONFIG_PM_WAKELOCKS_GC
    struct list_head    lru;
#endif
};

static struct rb_root wakelocks_tree = RB_ROOT;

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)) {
        wl = rb_entry(node, struct wakelock, node);
        if (wl->ws.active == show_active)
            str += scnprintf(str, end - str, "%s ", wl->name);
    }
    if (str > buf)
        str--;

    str += scnprintf(str, end - str, "\n");

    mutex_unlock(&wakelocks_lock);
    return (str - buf);
}

#if CONFIG_PM_WAKELOCKS_LIMIT > 0
static unsigned int number_of_wakelocks;

static inline bool wakelocks_limit_exceeded(void)
{
    return number_of_wakelocks > CONFIG_PM_WAKELOCKS_LIMIT;
}

static inline void increment_wakelocks_number(void)
{
    number_of_wakelocks++;
}

static inline void decrement_wakelocks_number(void)
{
    number_of_wakelocks--;
}
#else /* CONFIG_PM_WAKELOCKS_LIMIT = 0 */
static inline bool wakelocks_limit_exceeded(void) { return false; }
static inline void increment_wakelocks_number(void) {}
static inline void decrement_wakelocks_number(void) {}
#endif /* CONFIG_PM_WAKELOCKS_LIMIT */

#ifdef CONFIG_PM_WAKELOCKS_GC
#define WL_GC_COUNT_MAX 100
#define WL_GC_TIME_SEC  300

static LIST_HEAD(wakelocks_lru_list);
static unsigned int wakelocks_gc_count;

static inline void wakelocks_lru_add(struct wakelock *wl)
{
    list_add(&wl->lru, &wakelocks_lru_list);
}

static inline void wakelocks_lru_most_recent(struct wakelock *wl)
{
    list_move(&wl->lru, &wakelocks_lru_list);
}

static void wakelocks_gc(void)
{
    struct wakelock *wl, *aux;
    ktime_t now;

    if (++wakelocks_gc_count <= WL_GC_COUNT_MAX)
        return;

    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);
            decrement_wakelocks_number();
        }
    }
    wakelocks_gc_count = 0;
}
#else /* !CONFIG_PM_WAKELOCKS_GC */
static inline void wakelocks_lru_add(struct wakelock *wl) {}
static inline void wakelocks_lru_most_recent(struct wakelock *wl) {}
static inline void wakelocks_gc(void) {}
#endif /* !CONFIG_PM_WAKELOCKS_GC */

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;

        parent = *node;
        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;
    }
    if (!add_if_not_found)
        return ERR_PTR(-EINVAL);

    if (wakelocks_limit_exceeded())
        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);
    wakelocks_lru_add(wl);
    increment_wakelocks_number();
    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;

    if (!capable(CAP_BLOCK_SUSPEND))
        return -EPERM;

    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);
    }

    wakelocks_lru_most_recent(wl);

 out:
    mutex_unlock(&wakelocks_lock);
    return ret;
}

int pm_wake_unlock(const char *buf)
{
    struct wakelock *wl;
    size_t len;
    int ret = 0;

    if (!capable(CAP_BLOCK_SUSPEND))
        return -EPERM;

    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);

    wakelocks_lru_most_recent(wl);
    wakelocks_gc();

 out:
    mutex_unlock(&wakelocks_lock);
    return ret;
}