一：wakeup_source簡介：linux 3.4內核PM使用了wakeup_source來保持喚醒狀態，也就是keep awake。之前android一直是基于Linux加入了wake_lock機制來阻止系統休眠，后來Linux 3.4內核加入了wakeup_source來管理，安卓4.4跟著升級內核也就摒棄了自己的臃腫的wake_lock機制，在對上層接口并不改變，在內核wake_lock實現直接基于wakeup_source來實現的。當然也會帶來debug上的一些問題，比如以前的wake_lock自身帶有強大的debug信息，那么我們在調試的時候可以自己看見dmesg中默認打印active wake lock XXX，很直觀來辨別需要休眠的時候那個wake lock有問題阻止了休眠。這個需要我們自己來完善。個人認為改進很大，現在使用了autosleep機制，只要不存在任何active wakeup_source了，系統自動休眠，當有active wake_source自動block住，個人認為休眠更及時，非休眠時間在減少，同時不會消耗額外的資源。使用基于queue work與進程block來管理suspend。還有這里的wakeup_source個人覺得應該叫keepawake_source或者stayawake_souce，畢竟系統的喚醒也就是cpu的再次運行是由中斷喚醒的而不是wakeup_source。同時安卓4.4還有一個重大改變就是去除了early suspend機制改為fb event通知機制。那么現在就只有suspend與resume,runtime suspend與runtime resume了。/*** struct wakeup_source - Representation of wakeup sources** @total_time: Total time this wakeup source has been active.* @max_time: Maximum time this wakeup source has been continuously active.* @last_time: Monotonic clock when the wakeup source's was touched last time.* @prevent_sleep_time: Total time this source has been preventing autosleep.* @event_count: Number of signaled wakeup events.* @active_count: Number of times the wakeup sorce was activated.* @relax_count: Number of times the wakeup sorce was deactivated.* @expire_count: Number of times the wakeup source's timeout has expired.* @wakeup_count: Number of times the wakeup source might abort suspend.* @active: Status of the wakeup source.* @has_timeout: The wakeup source has been activated with a timeout.*/struct wakeup_source {const char ?? ??? ?*name;struct list_head?? ?entry;struct list_head?? ?list;spinlock_t?? ??? ?lock;struct timer_list?? ?timer;unsigned long?? ??? ?timer_expires; //超時時間，也就是wake_lock_timeout()里面的時間參數，超時后會執行deactivate函數ktime_t total_time;ktime_t max_time;ktime_t last_time;ktime_t start_prevent_time;ktime_t prevent_sleep_time;unsigned long?? ??? ?event_count; //event計數unsigned long?? ??? ?active_count;//active計數unsigned long?? ??? ?relax_count;unsigned long?? ??? ?expire_count;unsigned long?? ??? ?wakeup_count;bool?? ??? ??? ?active:1; //用于判斷是否是active狀態bool?? ??? ??? ?autosleep_enabled:1;//這個變量是來標記active等時間的};//active任何wakeup_source都會執行該函數，標記active為true/*** wakup_source_activate - Mark given wakeup source as active.* @ws: Wakeup source to handle.** Update the @ws' statistics and, if @ws has just been activated, notify the PM* core of the event by incrementing the counter of of wakeup events being* processed.*/static void wakeup_source_activate(struct wakeup_source *ws){unsigned int cec;ws->active = true;ws->active_count++;ws->last_time = ktime_get();if (ws->autosleep_enabled)ws->start_prevent_time = ws->last_time;/* Increment the counter of events in progress. */cec = atomic_inc_return(&combined_event_count);trace_wakeup_source_activate(ws->name, cec);}//deactivate任何wakeup_source都會執行該函數，標記active為false/*** wakup_source_deactivate - Mark given wakeup source as inactive.* @ws: Wakeup source to handle.** Update the @ws' statistics and notify the PM core that the wakeup source has* become inactive by decrementing the counter of wakeup events being processed* and incrementing the counter of registered wakeup events.*/static void wakeup_source_deactivate(struct wakeup_source *ws){unsigned int cnt, inpr, cec;ktime_t duration;ktime_t now;ws->relax_count++;/** __pm_relax() may be called directly or from a timer function.* If it is called directly right after the timer function has been* started, but before the timer function calls __pm_relax(), it is* possible that __pm_stay_awake() will be called in the meantime and* will set ws->active.? Then, ws->active may be cleared immediately* by the __pm_relax() called from the timer function, but in such a* case ws->relax_count will be different from ws->active_count.*/if (ws->relax_count != ws->active_count) {ws->relax_count--;return;}ws->active = false;now = ktime_get();duration = ktime_sub(now, ws->last_time);ws->total_time = ktime_add(ws->total_time, duration);if (ktime_to_ns(duration) > ktime_to_ns(ws->max_time))ws->max_time = duration;ws->last_time = now;del_timer(&ws->timer);ws->timer_expires = 0;if (ws->autosleep_enabled)update_prevent_sleep_time(ws, now);/** Increment the counter of registered wakeup events and decrement the* couter of wakeup events in progress simultaneously.*/cec = atomic_add_return(MAX_IN_PROGRESS, &combined_event_count);trace_wakeup_source_deactivate(ws->name, cec);split_counters(&cnt, &inpr);if (!inpr && waitqueue_active(&wakeup_count_wait_queue)){wake_up(&wakeup_count_wait_queue); //當不存在任何active wake_up source的時候喚醒try_to_suspend進程。}}wakup_source的申請與釋放：1：使用安卓的wake_lock接口：wake_lock()，wake_lock_timeout(),wake_unlock();2: 使用wakeup_source自帶的接口：pm_stay_awake(),pm_relax();這里的name就是device name。二：autosleep分析：

sys接口：sys/power/autosleep

亮屏時libsuspend會寫入off,滅屏寫入memstatic 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_SUSPENDif (state < PM_SUSPEND_MAX)return sprintf(buf, "%s\n", valid_state(state) ?pm_states[state] : "error");#endif#ifdef CONFIG_HIBERNATIONreturn sprintf(buf, "disk\n");#elsereturn 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&& strcmp(buf, "off") && strcmp(buf, "off\n"))return -EINVAL;error = pm_autosleep_set_state(state);return error ? error : n;}power_attr(autosleep);int pm_autosleep_set_state(suspend_state_t state){#ifndef CONFIG_HIBERNATIONif (state >= PM_SUSPEND_MAX)return -EINVAL;#endif__pm_stay_awake(autosleep_ws); //防止系統休眠mutex_lock(&autosleep_lock);autosleep_state = state;__pm_relax(autosleep_ws); //釋放上面的wake up sourceif (state > PM_SUSPEND_ON) {pm_wakep_autosleep_enabled(true); //設置所有wake up source里面的autosleep_enabled為真，這個變量不會對休眠有影響，但是會標記active的時間,使用debugfs可以看見queue_up_suspend_work();//調度工作隊列，會執行try_to_suspend()，其實state mem執行try_to_suspend()，一次就可以了，后面再分析。} else {pm_wakep_autosleep_enabled(false);//設置所有wake up source里面的autosleep_enabled為假}mutex_unlock(&autosleep_lock);return 0;}重頭戲：try_to_suspendstatic void try_to_suspend(struct work_struct *work){unsigned int initial_count, final_count;if (!pm_get_wakeup_count(&initial_count, true)) //獲取initial_count，這個函數會block住，當存在active wakeup source的時候，直到wakeup source為detative狀態goto out;mutex_lock(&autosleep_lock);if (!pm_save_wakeup_count(initial_count)) {//保存initial_count，不會block，當然也會檢查是否有active wakeup source，當有active存在再次queue work。mutex_unlock(&autosleep_lock);goto out;}if (autosleep_state == PM_SUSPEND_ON) {//當為ON狀態時，return。//在睡眠期間跟了很久沒有遇見過這種情況mutex_unlock(&autosleep_lock);return;}if (autosleep_state >= PM_SUSPEND_MAX)hibernate();????????????????? //hibernate高通平臺目前不支持elsepm_suspend(autosleep_state); //進入pm_suspend，dmesg會有PM: suspend entry 與PM: suspend exit來標記，這里面會執行freeze task,suspend與resume，disable cpu的操作。內核PM最重要的函數。mutex_unlock(&autosleep_lock);if (!pm_get_wakeup_count(&final_count, false))//獲取final_count，非block,當然也會檢查是否有active wakeup source，當有active存在再次queue workgoto 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)???????????? //這里遇見未知原因，initial_count與final_count相等，超時500ms后繼續往下執行。這種現象我也是跟了許久沒有遇見過。schedule_timeout_uninterruptible(HZ / 2);out:queue_up_suspend_work(); //調度queue work會再次執行該函數，實際上只要一次echo mem > sys/power/autosleep后這個進程一直會在auto_sleep cycle。}pm_get_wakeup_count原型,個人感覺這個是仿__wait_event_interruptible()而寫的。bool pm_get_wakeup_count(unsigned int *count, bool block){unsigned int cnt, inpr;if (block) { //當block為真時，該進程可能會block住DEFINE_WAIT(wait);for (;;) {prepare_to_wait(&wakeup_count_wait_queue, &wait,TASK_INTERRUPTIBLE);split_counters(&cnt, &inpr); //有active的wakeup_source存在就是block住，否則blockif (inpr == 0 || signal_pending(current))break;schedule();//在這里面block住，直到最后一個active的wakeup_source deactivate時會喚醒該進程，之后會break出來。}finish_wait(&wakeup_count_wait_queue, &wait);}split_counters(&cnt, &inpr);*count = cnt;return !inpr;}那么有2個問題，按power鍵喚醒系統是退出try_to_suspend了嗎？首先系統是如何被喚醒的？這個是由硬件中斷喚醒的，比如我們這里的power鍵，還有其他的比如alarm等其他硬件中斷，只要我們在中斷申請時enbale_irq_wake()，那么睡眠期間，只要觸發該中斷就可以喚醒系統。那么在try_to_suspend里面喚醒后pm_suspend()執行完resume后會退出來，接著會獲取final_count，在這里是存在activewake_up source的(在out之前加添的打印active wakeup_source，下面的dmesg證明了存在的wakeup_source)，之后執行out,后調度工作隊列，再次進入try_to_suspend()，在第一次獲取initial_count后便會遇見active wakeup_source，這里面更多的是系統上層加的wakeup_source，那么try_to_suspend()會一直block在pm_get_wakeup_count()里面直到滅屏和所有wakeup_source deactivate時會再次進入pm_suspend()休眠。這里也就解釋了為什么只要執行一次ehco mem > sys/power/autosleep后自動可以休眠了的原因。看下面的dmesg:<6>[? 928.536418] CPU0: msm_cpu_pm_enter_sleep mode 000000,00000000,00000000,00000000,00000000,00000020,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000<6>[? 928.543066] PM: noirq resume of devices complete after 6.020 msecs<6>[? 928.548512] PM: early resume of devices complete after 2.598 msecs<6>[? 928.650793] PM: resume of devices complete after 102.266 msecs<6>[? 928.660290] Restarting tasks ... done.<6>[? 928.681208] PM: suspend exit 1970-01-05 05:23:32.206389881 UTC<6>[? 928.681229] active wake lock KeyEvents<6>[? 928.681267] active wake lock qpnp_soc_wake<6>[? 928.681284] active wake lock alarm, time left 486<6>[? 928.681342] active wake lock KeyEvents<6>[? 928.681584] active wake lock qpnp_soc_wake<6>[? 928.681600] active wake lock alarm, time left 486<6>[? 928.696345] request_suspend_state: wakeup at 928691792356 (1970-01-05 05:23:32.221521704 UTC)<6>[? 928.708608] mdss_dsi_panel_power on=1還有一個與wakeup source無關的問題,為什么suspend后就一直停留在那里不動了？這個是cpu停止運轉了，下面再分析下代碼。核心函數suspend_devices_and_enter()：/*** suspend_devices_and_enter - Suspend devices and enter system sleep state.* @state: System sleep state to enter.*/int suspend_devices_and_enter(suspend_state_t state){int error;bool wakeup = false;if (!suspend_ops)return -ENOSYS;trace_machine_suspend(state);if (suspend_ops->begin) {error = suspend_ops->begin(state);if (error)goto Close;}suspend_console();suspend_test_start();error = dpm_suspend_start(PMSG_SUSPEND);//這里會執行所有driver的suspend函數，suspend里面有active wakeup_source或者return 為真的話，suspend會報錯if (error) {printk(KERN_ERR "PM: Some devices failed to suspend\n");goto Recover_platform;}suspend_test_finish("suspend devices");if (suspend_test(TEST_DEVICES))goto Recover_platform;do {error = suspend_enter(state, &wakeup);//這里會diable cpu} while (!error && !wakeup&& suspend_ops->suspend_again && suspend_ops->suspend_again());Resume_devices:suspend_test_start();dpm_resume_end(PMSG_RESUME);suspend_test_finish("resume devices");resume_console();Close:if (suspend_ops->end)suspend_ops->end();trace_machine_suspend(PWR_EVENT_EXIT);return error;Recover_platform:if (suspend_ops->recover)suspend_ops->recover();goto Resume_devices;}static int suspend_enter(suspend_state_t state, bool *wakeup){int error;if (suspend_ops->prepare) {error = suspend_ops->prepare();if (error)goto Platform_finish;}error = dpm_suspend_end(PMSG_SUSPEND);if (error) {printk(KERN_ERR "PM: Some devices failed to power down\n");goto Platform_finish;}if (suspend_ops->prepare_late) {error = suspend_ops->prepare_late();if (error)goto Platform_wake;}if (suspend_test(TEST_PLATFORM))goto Platform_wake;error = disable_nonboot_cpus();? //disable nonboot cpu注意還有cpu需要下面disable的if (error || suspend_test(TEST_CPUS))goto Enable_cpus;arch_suspend_disable_irqs();BUG_ON(!irqs_disabled());error = syscore_suspend();if (!error) {*wakeup = pm_wakeup_pending();if (!(suspend_test(TEST_CORE) || *wakeup)) {error = suspend_ops->enter(state); //在這里cpu會停止運行，直到中斷喚醒//下面的全部是喚醒的操作了events_check_enabled = false;}syscore_resume();}arch_suspend_enable_irqs();BUG_ON(irqs_disabled());Enable_cpus:enable_nonboot_cpus();Platform_wake:if (suspend_ops->wake)suspend_ops->wake();dpm_resume_start(PMSG_RESUME);Platform_finish:if (suspend_ops->finish)suspend_ops->finish();return error;}平臺賦值，這里debug平臺是基于msm8974的：static const struct platform_suspend_ops lpm_suspend_ops = {.enter = lpm_suspend_enter,//在這里面disbale cpu，停止運行程序.valid = suspend_valid_only_mem,.prepare_late = lpm_suspend_prepare,.wake = lpm_suspend_wake,};添加顯示wake_lock的dmesg:<6>[?? 90.964850] CPU0: msm_cpu_pm_enter_sleep mode 000000,00000000,00000000,00000000,00000000,00000020,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000<6>[?? 90.965302] Enabling non-boot CPUs ...<6>[?? 90.968303] CPU3 is up<6>[?? 90.970699] PM: noirq resume of devices complete after 2.382 msecs<6>[?? 90.973460] PM: early resume of devices complete after 1.443 msecs<6>[?? 91.097369] PM: resume of devices complete after 123.888 msecs<6>[?? 91.112858] Restarting tasks ... done.<6>[?? 91.141699] PM: suspend exit 1970-01-05 03:59:28.158266979 UTC<6>[?? 91.141776] PM: suspend entry 1970-01-05 03:59:28.158347917 UTC<6>[?? 91.141801] PM: Syncing filesystems ... done.<6>[?? 91.222299] Freezing user space processes ... (elapsed 0.03 seconds) done.<6>[?? 91.258126] Freezing remaining freezable tasks ... (elapsed 0.02 seconds) done.<6>[?? 91.278279] Suspending console(s) (use no_console_suspend to debug)<6>[?? 91.384933] PM: suspend of devices complete after 95.062 msecs<6>[?? 91.397910] PM: late suspend of devices complete after 12.934 msecs<6>[?? 91.413019] PM: noirq suspend of devices complete after 15.064 msecs<6>[?? 91.413059] Disabling non-boot CPUs ...<6>[?? 91.424477] CPU0: msm_cpu_pm_enter_sleep mode 000000,00000000,00000000,00000000,00000000,00000020,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000//這里cpu停止運行直到中斷喚醒<6>[?? 91.425144] Enabling non-boot CPUs ...<6>[?? 91.432354] CPU3 is up<6>[?? 91.444416] PM: noirq resume of devices complete after 11.997 msecs<6>[?? 91.460948] PM: early resume of devices complete after 10.458 msecs<6>[?? 91.577213] PM: resume of devices complete after 116.231 msecs<6>[?? 91.584876] Restarting tasks ... done.<6>[?? 91.614571] PM: suspend exit 1970-01-05 03:59:35.550203849 UTC<6>[?? 91.614639] active wake lock rmt_storage_-1220268312<6>[?? 91.689912] PM: suspend entry 1970-01-05 03:59:35.625550620 UTC<6>[?? 91.689921] PM: Syncing filesystems ... done.<6>[?? 91.700706] Freezing user space processes ...<3>[?? 91.712870] Freezing of user space? aborted<6>[?? 91.712898]<6>[?? 91.712903] Restarting tasks ... done.<6>[?? 91.720540] PM: suspend exit 1970-01-05 03:59:35.656175256 UTC<6>[?? 91.720574] PM: suspend entry 1970-01-05 03:59:35.656214579 UTC<6>[?? 91.720586] PM: Syncing filesystems ... done.<6>[?? 91.801097] Freezing user space processes ...<3>[?? 91.815050] Freezing of user space? aborted<6>[?? 91.815075]<6>[?? 91.815083] Restarting tasks ... done.<6>[?? 91.823603] PM: suspend exit 1970-01-05 03:59:35.759241558 UTC<6>[?? 91.823633] PM: suspend entry 1970-01-05 03:59:35.759272964 UTC<6>[?? 91.823643] PM: Syncing filesystems ... done.<6>[?? 91.911985] Freezing user space processes ... (elapsed 0.03 seconds) done.<6>[?? 91.949378] Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done.<6>[?? 91.969089] Suspending console(s) (use no_console_suspend to debug)<6>[?? 92.085594] PM: suspend of devices complete after 98.499 msecs<6>[?? 92.098615] PM: late suspend of devices complete after 12.975 msecs<6>[?? 92.113909] PM: noirq suspend of devices complete after 15.249 msecs<6>[?? 92.113951] Disabling non-boot CPUs ...<6>[?? 92.147320] CPU0: msm_cpu_pm_enter_sleep mode 000000,00000000,00000000,00000000,00000000,00000020,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000<6>[?? 92.148265] Enabling non-boot CPUs ...<6>[?? 92.155121] CPU1 is up<6>[?? 92.163797] CPU2 is up<6>[?? 92.174144] CPU3 is up<6>[?? 92.186556] PM: noirq resume of devices complete after 12.344 msecs<6>[?? 92.199945] PM: early resume of devices complete after 10.020 msecs<6>[?? 92.317528] PM: resume of devices complete after 117.548 msecs<6>[?? 92.326254] Restarting tasks ... done.<6>[?? 92.342025] PM: suspend exit 1970-01-05 04:00:48.122436614 UTC<6>[?? 92.342337] active wake lock qpnp-vadc-f611ac00

<6>[?? 92.342357] active wake lock alarm, time left 481<6>[?? 92.411428] PM: suspend entry 1970-01-05 04:00:48.191838905 UTC<6>[?? 92.411451] PM: Syncing filesystems ... done.<6>[?? 92.419086] Freezing user space processes ...<3>[?? 92.431173] Freezing of user space? aborted<6>[?? 92.431213]<6>[?? 92.431225] Restarting tasks ... done.<6>[?? 92.441575] PM: suspend exit 1970-01-05 04:00:48.221987864 UTC<6>[?? 92.441709] active wake lock qpnp-vadc-f611ac00<6>[?? 92.445004] PM: suspend entry 1970-01-05 04:00:48.225417551 UTC<6>[?? 92.445026] PM: Syncing filesystems ... done.<6>[?? 92.525764] Freezing user space processes ...<3>[?? 92.541465] Freezing of user space? aborted<6>[?? 92.541523]<6>[?? 92.541545] Restarting tasks ... done.<6>[?? 92.558768] PM: suspend exit 1970-01-05 04:00:48.339166145 UTC<6>[?? 92.558865] PM: suspend entry 1970-01-05 04:00:48.339268645 UTC<6>[?? 92.558898] PM: Syncing filesystems ... done.<6>[?? 92.656122] Freezing user space processes ... (elapsed 0.04 seconds) done.<6>[?? 92.699091] Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done.<6>[?? 92.718891] Suspending console(s) (use no_console_suspend to debug)<6>[?? 92.832084] PM: suspend of devices complete after 97.905 msecs<6>[?? 92.845099] PM: late suspend of devices complete after 12.971 msecs<6>[?? 92.860407] PM: noirq suspend of devices complete after 15.264 msecs<6>[?? 92.860447] Disabling non-boot CPUs ...<6>[?? 92.895114] CPU0: msm_cpu_pm_enter_sleep mode 000000,00000000,00000000,00000000,00000000,00000020,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000

總結

以上是生活随笔為你收集整理的linux wakeup,linux内核3.4基于wakeup的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。