Input ANR處理流程

ANR時間區別便是指當前這次的事件dispatch過程中執行findFocusedWindowTargetsLocked()方法到下一次執行resetANRTimeoutsLocked()的時間區間. 以下5個時機會reset. 都位於InputDispatcher.cpp文件:

• resetAndDropEverythingLocked
• releasePendingEventLocked
• setFocusedApplication
• dispatchOnceInnerLocked
• setInputDispatchMode

簡單來說, 上面方法主要是對應以下4個場景,會有機會執行resetANRTimeoutsLocked重置timeout時間:

• 解凍屏幕, 系統開/關機的時刻點 (thawInputDispatchingLw, setEventDispatchingLw)
• wms聚焦app的改變 (WMS.setFocusedApp, WMS.removeAppToken)
• 設置input filter的過程 (IMS.setInputFilter)
• 再次分發事件的過程(dispatchOnceInnerLocked)

當InputDispatcher線程 findFocusedWindowTargetsLocked()過程調用到handleTargetsNotReadyLocked，且滿足超時5s的情況則會調用onANRLocked().

通過將InputManagerService加入到Watchdog的monitor隊列,定時監測是否發生死鎖. 整個監測過涉及EventHub, InputReader, InputDispatcher, InputManagerService的死鎖監測. 監測的原理很簡單,通過嘗試獲取鎖並釋放鎖的方式.

可通過adb shell dumpsys input來查看手機當前的input狀態, 輸出內容分別為EventHub.dump(), InputReader.dump(),InputDispatcher.dump()這3類,另外如果發生過input ANR,那么也會輸出上一個ANR的狀態.

其中mPendingEvent代表的當下正在處理的事件.

ANR分類

由小節[3.5] InputMonitor.notifyANR完成, 當發生ANR時system log中會出現以下信息, 並且TAG=WindowManager:

Input event dispatching timed out xxx. Reason: + reason, 其中xxx取值:

• 窗口類型: sending to windowState.mAttrs.getTitle()
• 應用類型: sending to application appWindowToken.stringName
• 其他類型: 則為空.

至於Reason主要有以下類型:

5.1.1 reason類型

由checkWindowReadyForMoreInputLocked完成， ANR reason主要有以下幾類：

1. 無窗口, 有應用：Waiting because no window has focus but there is a focused application that may eventually add a window when it finishes starting up.
2. 窗口暫停: Waiting because the [targetType] window is paused.
3. 窗口未連接: Waiting because the [targetType] window’s input channel is not registered with the input dispatcher. The window may be in the process of being removed.
4. 窗口連接已死亡：Waiting because the [targetType] window’s input connection is [Connection.Status]. The window may be in the process of being removed.
5. 窗口連接已滿：Waiting because the [targetType] window’s input channel is full. Outbound queue length: [outboundQueue長度]. Wait queue length: [waitQueue長度].
6. 按鍵事件，輸出隊列或事件等待隊列不為空：Waiting to send key event because the [targetType] window has not finished processing all of the input events that were previously delivered to it. Outbound queue length: [outboundQueue長度]. Wait queue length: [waitQueue長度].
7. 非按鍵事件，事件等待隊列不為空且頭事件分發超時500ms：Waiting to send non-key event because the [targetType] window has not finished processing certain input events that were delivered to it over 500ms ago. Wait queue length: [waitQueue長度]. Wait queue head age: [等待時長].

其中

• targetType: 取值為”focused”或者”touched”
• Connection.Status: 取值為”NORMAL”，”BROKEN”，”ZOMBIE”

另外, findFocusedWindowTargetsLocked, findTouchedWindowTargetsLocked這兩個方法中可以通過實現 updateDispatchStatisticsLocked()來分析anr問題.

drop事件分類

由dropInboundEventLocked完成，輸出事件丟棄的原因：

1. DROP_REASON_POLICY: “inbound event was dropped because the policy consumed it”;
2. DROP_REASON_DISABLED: “inbound event was dropped because input dispatch is disabled”;
3. DROP_REASON_APP_SWITCH: “inbound event was dropped because of pending overdue app switch”;
4. DROP_REASON_BLOCKED: “inbound event was dropped because the current application is not responding and the user has started interacting with a different application””;
5. DROP_REASON_STALE: “inbound event was dropped because it is stale”;

其他:

• doDispatchCycleFinishedLockedInterruptible的過程, 會記錄分發時間超過2s的事件,
• findFocusedWindowTargetsLocked的過程, 可以統計等待時長信息.