android 和linux的休眠唤醒机制.doc

android 和linux的休眠唤醒机制 四、android层源码解析1.hardware/libhardware_legacy/power/power.c /HAI层2. frameworks/base/core/jni/android_os_Power.cpp /jni层3frameworks/base/core/java/android/os/Power.java /java层在linux之上经过android的软件堆层层封装,最终在上层的java应用程序中使用。休眠唤醒也是从最上层发出的命令，然后一层一层地将参数解析，往最底层传，最后走上标准linux的休眠唤醒之路。这一部分将会初略分析休眠唤醒机制上linux之上所走的路线。在linux之上，存在一个hal层，专门做和linux内核设备打交道的事情，这里也不例外。休眠唤醒机制的hal层源码位于：hardware/libhardware_legacy/power/power.c该文件源码比较简单，下面列举重点片段：enum ACQUIRE_PARTIAL_WAKE_LOCK = 0,RELEASE_WAKE_LOCK,REQUEST_STATE,OUR_FD_COUNT;const char * const NEW_PATHS = /sys/power/wake_lock,/sys/power/wake_unlock,/sys/power/state;static int g_initialized = 0;static int g_fdsOUR_FD_COUNT;static const char *off_state = mem;static const char *on_state = on;static int open_file_descriptors(const char * const paths)int i;for (i=0; iOUR_FD_COUNT; i+) int fd = open(pathsi, O_RDWR);if (fd 0) fprintf(stderr, fatal error opening %sn, pathsi);g_error = errno;return -1;g_fdsi = fd;g_error = 0;return 0;static inline void initialize_fds(void)if (g_initialized = 0) if(open_file_descriptors(NEW_PATHS) = 0;int set_screen_state(int on)QEMU_FALLBACK(set_screen_state(on);LOGI(* set_screen_state %d, on);initialize_fds();if (g_error) return g_error;char buf32;int len;if(on)len = sprintf(buf, on_state);elselen = sprintf(buf, off_state);len = write(g_fdsREQUEST_STATE, buf, len);if(len GetStringUTFChars(idObj, NULL);acquire_wake_lock(lock, id);env-ReleaseStringUTFChars(idObj, id);/ 对wakelock加锁函数static void releaseWakeLock(JNIEnv *env, jobject clazz, jstring idObj)if (idObj = NULL) throw_NullPointerException(env, id is null);return ;const char *id = env-GetStringUTFChars(idObj, NULL);release_wake_lock(id);env-ReleaseStringUTFChars(idObj, id);/ 对wakelock解锁函数static int setScreenState(JNIEnv *env, jobject clazz, jboolean on)return set_screen_state(on);/ 休眠唤醒的函数Jni的方法需要注册到上层才可以使用，同时也需要在上层的对应java类中声明了native才可以使用。那么这里的方法在java中对应的声明在哪里呢？frameworks/base/core/java/android/os/Power.java，该文件定义一个java类，如下：public class Power/ cant instantiate this classprivate Power()/* Wake lock that ensures that the CPU is running. The screen might* not be on.*/public static final int PARTIAL_WAKE_LOCK = 1;/* Wake lock that ensures that the screen is on.*/public static final int FULL_WAKE_LOCK = 2;public static native void acquireWakeLock(int lock, String id);public static native void releaseWakeLock(String id); /* Turn the screen on or off* param on Whether you want the screen on or off*/public static native int setScreenState(boolean on);声明的jni接口应该是被java server在使用，这里就是专门的电源管理服务：PowerManagerService使用，具体源码位置在：frameworks/base/services/java/com/android/server/PowerManagerService.java。android在最上层还提供了现场的android.os.PowerManager类(frameworks/base/core/java/android/os/PowerManager.java)来供app使用，PowerManager类会调用java服务PowerManagerService的方法来完成与wakelock相关的工作。 frameworks/base/core/java/android/os/PowerManager.java类PowerManager中内嵌了一个WakeLock类，另外还定义了wakelock的类型，下面是代码片段：public class PowerManagerprivate static final String TAG = PowerManager;/* Wake lock that ensures that the CPU is running. The screen might* not be on.*/public static final int PARTIAL_WAKE_LOCK = WAKE_BIT_CPU_STRONG;/* Wake lock that ensures that the screen and keyboard are on at* full brightness.*/public static final int FULL_WAKE_LOCK = WAKE_BIT_CPU_WEAK | WAKE_BIT_SCREEN_BRIGHT | WAKE_BIT_KEYBOARD_BRIGHT;/* Wake lock that ensures that the screen is on at full brightness;* the keyboard backlight will be allowed to go off.*/public static final int SCREEN_BRIGHT_WAKE_LOCK = WAKE_BIT_CPU_WEAK | WAKE_BIT_SCREEN_BRIGHT;/* Wake lock that ensures that the screen is on (but may be dimmed);* the keyboard backlight will be allowed to go off.*/public static final int SCREEN_DIM_WAKE_LOCK = WAKE_BIT_CPU_WEAK | WAKE_BIT_SCREEN_DIM;/* Wake lock that turns the screen off when the proximity sensor activates.* Since not all devices have proximity sensors, use* link #getSupportedWakeLockFlags() getSupportedWakeLockFlags() to determine if* this wake lock mode is supported.* hide*/public static final int PROXIMITY_SCREEN_OFF_WAKE_LOCK = WAKE_BIT_PROXIMITY_SCREEN_OFF;public class WakeLockWakeLock(int flags, String tag)switch (flags & LOCK_MASK) case PARTIAL_WAKE_LOCK:case SCREEN_DIM_WAKE_LOCK:case SCREEN_BRIGHT_WAKE_LOCK:case FULL_WAKE_LOCK:case PROXIMITY_SCREEN_OFF_WAKE_LOCK:break;default:throw new IllegalArgumentException();mFlags = flags;mTag = tag;mToken = new Binder();public void acquire()synchronized (mToken) if (!mRefCounted | mCount+ = 0) try mService.acquireWakeLock(mFlags, mToken, mTag); catch (RemoteException e) mHeld = true;public void release(int flags)synchronized (mToken) if (!mRefCounted | -mCount = 0) try mService.releaseWakeLock(mToken, flags); catch (RemoteException e) mHeld = false;if (mCount 0) throw new RuntimeException(WakeLock under-locked + mTag);public WakeLock newWakeLock(int flags, String tag)if (tag = null) throw new NullPointerException(tag is null in PowerManager.newWakeLock);return new WakeLock(flags, tag);public void goToSleep(long time) try mService.goToSleep(time); catch (RemoteException e) public PowerManager(IPowerManager service, Handler handler)mService = service; 21:40 评论 / 浏览 (0 / 378)2011-05-29缩略显示Android在标准linux基础上对休眠唤醒的实现(二)LinuxAndroid活动工作三、kernel层源码解析 - wakelock的重要地位wakelock在android的休眠唤醒机制中扮演着及其重要的角色，主要源码位于文件:kernel/kernel/power/wakelock.c，kernel/include/linux/wakelock.h中。wakelocks_init()函数所做的工作是整个wakelock可以工作起来的基础，所有这里先说说这个函数。static int _init wakelocks_init(void)int ret;int i;for (i = 0; i flags & WAKE_LOCK_ACTIVE) lock-flags |= WAKE_LOCK_ACTIVE;/ wakelock状态为inactive，则更改为activeif (has_timeout) / wake_lock_timeout()会传入1if (wakelock_debug_mask & DEBUG_WAKE_LOCK)pr_info(wake_lock_internal: %s, type %d, timeout %ld.%03lun,lock-name, type, timeout / HZ,(timeout % HZ) * MSEC_PER_SEC / HZ);lock-expires = jiffies + timeout; / 设置超时时间lock-flags |= WAKE_LOCK_AUTO_EXPIRE; / 超时锁标志list_add_tail(&lock-link, &active_wake_lockstype); / acquire a non-timeout wakelock 添加一个非超时锁else / wake_lock ()会传入0if (wakelock_debug_mask & DEBUG_WAKE_LOCK)pr_info(wake_lock_internal: %s, type %dn, lock-name, type);lock-expires = LONG_MAX; / 设置成超时时间最大值lock-flags &= WAKE_LOCK_AUTO_EXPIRE; / 非超时锁标志list_add(&lock-link, &active_wake_lockstype);/ 将刚刚设置的非超时锁加到对应类型的活动锁链表中解锁的时候，这两种形式的锁所使用函数都是一样了：wake_unlock()，该函数中会首先作如下操作：lock-flags &= (WAKE_LOCK_ACTIVE | WAKE_LOCK_AUTO_EXPIRE);/ 清除锁活动标志和自动超时标志list_del(&lock-link); / 从锁对应的活动链表上摘除list_add(&lock-link, &inactive_locks); / 将unlock的锁挂接到非活动链表inactive_locks上前面已经说了只有类型为WAKE_LOCK_SUSPEND的wakelock被上锁才会阻止系统进入suspend，那么也就是说只要链表active_wake_locksWAKE_LOCK_SUSPEND为NULL，那么系统就可以执行suspend的流程了。Android对linux的改造，让其可以在三种情况下进入linux的标准suspend的流程：1. wake_unlock()，这个应该是最容易想到的，只要系统有对WAKE_LOCK_SUSPEND类型的wakelock解锁的动作，都有可能会进入suspend流程开始休眠，为什么是有可能呢？因为可能还有超时锁没有被超时解锁。下面看一下代码片段：void wake_unlock(struct wake_lock *lock)if (type = WAKE_LOCK_SUSPEND) / 貌似只在处理这个类型的wakelocklong has_lock = has_wake_lock_locked(type);/ 这个函数蛮重要，它来检查type类型的链表上是否还有锁被上锁了。/ 其返回值如果是0，说明没有该类型的锁被持有了；返回非0表明就是这个类型的活动链表上还存在超时锁但是没有非超时锁了，这个返回值就是当前时间距离最后超时的锁超时时间的jiffies值；如果返回-1，那表明还有该类型的非超时锁被持有。if (wakelock_debug_mask & DEBUG_WAKE_LOCK)pr_info(wake_unlock: has_lock = 0x%xn , has_lock); if (has_lock 0) if (wakelock_debug_mask & DEBUG_EXPIRE)pr_info(wake_unlock: %s, start expire timer, %ldn, lock-name, has_lock);mod_timer(&expire_timer, jiffies + has_lock);/ 修改定时器的超时值并add该定时器 else / 已经没有超时锁了if (del_timer(&expire_timer) / 删除定时器if (wakelock_debug_mask & DEBUG_EXPIRE)pr_info(wake_unlock: %s, stop expire timern, lock-name);if (has_lock = 0) / !=0,表明还有该类型的非超时锁被持有，现在还不能进入suspendpr_info(wake_unlock: (%s) suspend_work_queue suspend_workn , lock-name);queue_work(suspend_work_queue, &suspend_work);/ 提交suspend的工作项，开始执行标准linux的suspend流程 spin_unlock_irqrestore(&list_lock, irqflags);2. 超时锁超时之后，定时器的回调函数会执行会查看是否有其他的wakelock, 如果没有, 就在这里让系统进入睡眠。static void expire_wake_locks(unsigned long data)long has_lock;unsigned long irqflags;if (debug_mask & DEBUG_EXPIRE)pr_info(expire_wake_locks: startn);spin_lock_irqsave(&list_lock, irqflags);if (debug_mask & DEBUG_SUSPEND)print_active_locks(WAKE_LOCK_SUSPEND);has_lock = has_wake_lock_locked(WAKE_LOCK_SUSPEND);if (debug_mask & DEBUG_EXPIRE)pr_info(expire_wake_locks: done, has_lock %ldn, has_lock);if (has_lock = 0)/ 如果没有SUSPEND类型的wakelock处于active，那么将调用suspendqueue_work(suspend_work_queue, &suspend_work);spin_unlock_irqrestore(&list_lock, irqflags);static DEFINE_TIMER(expire_timer, expire_wake_locks, 0, 0);列出以下一个重要的函数源码：static long has_wake_lock_locked(int type)struct wake_lock *lock, *n;long max_timeout = 0;BUG_ON(type = WAKE_LOCK_TYPE_COUNT);list_for_each_entry_safe(lock, n, &active_wake_lockstype, link) if (lock-flags & WAKE_LOCK_AUTO_EXPIRE) long timeout = lock-expires - jiffies;if (timeout max_timeout)max_timeout = timeout; elsereturn -1;return max_timeout;3. 这个可能有人觉得匪夷所思，就是在wake_lock_ _timeout()函数中，调用了内部函数wake_lock_internal()。这里只有在对超时锁上锁的时候才有可能进入休眠，如果对一个费超时锁上锁的话，那么就没有必要去检查活动链表了。static void wake_lock_internal(struct wake_lock *lock, long timeout, int has_timeout)if (type = WAKE_LOCK_SUSPEND) current_event_num+;#ifdef CONFIG_WAKELOCK_STATif (lock = &main_wake_lock)update_sleep_wait_stats_locked(1);else if (!wake_lock_active(&main_wake_lock)update_sleep_wait_stats_locked(0);#endifif (has_timeout) / 超时锁的时候传进来的是1expire_in = has_wake_lock_locked(type);/ 检查当前锁类型链表上是否还有锁处于active的状态，无返回0elseexpire_in = -1; / 如果是非超时锁的话，这里直接赋值-1，省去了活动链表检查步骤了if (expire_in 0) if (debug_mask & DEBUG_EXPIRE)pr_info(wake_lock: %s, start expire timer, %ldn, lock-name, expire_in);/ modify the time wakelock is expiredmod_timer(&expire_timer, jiffies + expire_in); else if (del_timer(&expire_timer)if (debug_mask & DEBUG_EXPIRE) 21:33 评论 / 浏览 (0 / 860)2011-05-29缩略显示新版linux系统设备架构中关于电源管理方式的变更Linux数据结构新版linux系统设备架构中关于电源管理方式的变更based on linux-2.6.32一、设备模型各数据结构中电源管理的部分linux的设备模型通过诸多结构体来联合描述，如struct device，struct device_type，struct class，struct device_driver，struct bus_type等。kernel/include/linux/devices.h中有这几中结构体的定义，这里只列出和PM有关的项，其余查看源码：struct device.struct dev_pm_infopower; .struct device_type .int (*uevent)(struct device *dev, struct kobj_uevent_env *env);char *(*devnode)(struct device *dev, mode_t *mode);void (*release)(struct device *dev);const struct dev_pm_ops *pm;struct class .void (*class_release)(struct class *class);void (*dev_release)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);const struct dev_pm_ops *pm;.;struct device_driver .int (*probe) (struct device *dev);int (*remove) (struct device *dev);void (*shutdown) (struct device *dev);int (*suspend) (struct device *dev, pm_message_t state);int (*resume) (struct device *dev);const struct dev_pm_ops *pm;.;struct bus_type .int (*match)(struct device *dev, struct device_driver *drv);int (*uevent)(struct device *dev, struct kobj_uevent_env *env);int (*probe)(struct device *dev);int (*remove)(struct device *dev);void (*shutdown)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);const struct dev_pm_ops *pm;.;以上可以看出和电源管理相关的两个结构体是struct dev_pm_info和struct dev_pm_ops，他们定义于文件kernel/include/linux/pm.hstruct dev_pm_info pm_message_tpower_state;unsigned intcan_wakeup:1;unsigned intshould_wakeup:1;enum dpm_statestatus;/* Owned by the PM core - 表示该设备当前的PM状态*/#ifdef CONFIG_PM_SLEEPstruct list_headentry;/* 链接到dpm_list全局链表中的连接体 */#endif#ifdef CONFIG_PM_RUNTIME/ undefstruct timer_listsuspend_timer;unsigned longtimer_expires;struct work_structwork;wait_queue_head_twait_queue;spinlock_tlock;atomic_tusage_count;atomic_tchild_count;unsigned intdisable_depth:3;unsigned intignore_children:1;unsigned intidle_notification:1;unsigned intrequest_pending:1;unsigned intdeferred_resume:1;enum rpm_requestrequest;enum rpm_statusruntime_status;intruntime_error;#endif;struct dev_pm_ops int (*prepare)(struct device *dev);void (*complete)(struct device *dev);int (*suspend)(struct device *dev);int (*resume)(struct device *dev);int (*freeze)(struct device *dev);int (*thaw)(struct device *dev);int (*poweroff)(struct device *dev);int (*restore)(struct device *dev);int (*suspend_noirq)(struct device *dev);int (*resume_noirq)(struct device *dev);int (*freeze_noirq)(struct device *dev);int (*thaw_noirq)(struct device *dev);int (*poweroff_noirq)(struct device *dev);int (*restore_noirq)(struct device *dev);int (*runtime_suspend)(struct device *dev);int (*runtime_resume)(struct device *dev);int (*runtime_idle)(struct device *dev);二、device中的dev_pm_info结构体device结构体中的power项用来将该设备纳入电源管理的范围，记录电源管理的一些信息。在注册设备的时候调用函数device_add()来向sysfs系统添加power接口和注册进电源管理系统，代码片段如下：.error = dpm_sysfs_add(dev);kernel/drivers/base/power/sysfs.cif (error)goto DPMError;device_pm_add(dev);kernel/drivers/base/power/main.c.其中dpm_sysfs_add()函数用来向sysfs文件系统中添加相应设备的power接口文件，如注册mt6516_tpd paltform device的时候，会在sysfs中出现如下目录和文件：#pwd/sys/devices/platform/mt6516-tpd#cd mt6516-tpd#ls -l-rw-r-r- root root 4096 2010-01-02 06:35 uevent-r-r-r- root root 4096 2010-01-02 06:39 modaliaslrwxrwxrwx root root 2010-01-02 06:39 subsystem - ./././bus/platformdrwxr-xr-x root root 2010-01-02 06:35 powerlrwxrwxrwx root root 2010-01-02 06:39 driver - ./././bus/platform/drivers/mt6516-tpd#cd power#l