死机的可能原因？死机问题需要分析哪些数据？

一、死机系统简图

当用户对手机进行操作时, 对应的数据流将是下面一个概括的流程图.

HW 如传感器, 触摸屏(TP), 物理按键(KP)等感知到用户操作后，触发相关的中断(ISR) 传递给Kernel, Kernel 相关的driver 对这些ISR 进行处理后，转化成标准的InputEvent.

User Space 的System Server 中的Input System 则持续监听Kernel 传递上来的原始InputEvent, 对其进行进一步的处理后, 变成上层APP 可直接处理的Input Event, 如button 点击, 长按, 滑动等等.

APP 对相关的事件进行处理后，请求更新相关的逻辑界面，而这个则由System Server 中的WMS 等来负责.

相关的逻辑界面更新后(Z-Window), 则会请求SurfaceFlinger 来产生FrameBuffer 数据, SurfaceFlinger 则会利用GPU 等来计算生成.

Display System/Driver 则会将FrameBuffer 中的数据更新显示出来, 这样用户才能感知到他的操作行为.

二、死机的可能原因

原则上上面流程中，每一步出现问题，都可能引发死机问题. 大的方面讲，可以分成 硬件HW 和 软件SW 两个层次, 硬件HW 不在我们的讲诉之内.

1.软件SW 上，死机的原因可以分成两种:

逻辑行为异常

逻辑判断错误

逻辑设计错误

逻辑卡顿(block)

死循环 (Deadloop)

死锁 (Deadlock)

2.从具体的原因上将，可以进一步分成:

(1). Input Driver

无法接收HW 的中ISR，产生原始的InputEvent, 或者产生的InputEvent 异常.

(2). Input System

无法监听Kernel 传递上来的原始InputEvent, 或者转换与传递异常.

(3). System Logic

无法正常响应Input System 传递过来的InputEvent, 或者响应出错.

(4). WMS/Surfaceflinger 行为异常

WMS/SF 无法正确的对Z-Window 进行叠加转换

(5). Display System3

无法更新Framebuffer 数据，或者填充的数据错误

(6). LCM Driver

无法将Framebuffer 数据显示在LCM 上

(7). CPU Scheduler/File System/Memory Manager 等Kernel 支撑性模块.

系统支撑性模块无法正常, 导致整个流程都没法正常进行, 如CPU Scheduler 无法正常执行,导致thread 都无法被调度, memory 耗尽导致系统无法快速申请到memory, file system 卡住导致无法进行读写操作等.

3. 对应硬件HW hang, 经常见得的情况有:

Power 异常

Clock/26M/32K 失效

CPU Core 无法启动, 执行异常等.

Memory & Memory Controller.

Fail IC.

三、死机问题需要分析哪些数据

1. 死机分析数据

俗话说, 巧妇难为无米之炊, 死机分析, 同样需要获取第一手的资料, 方可分析问题. 那么哪些数据可以用来分析死机呢。
大概的讲，可以分成空间数据和时间数据。空间数据，即当时现场环境，如有哪些process 在运行，CPU 的执行情况，memory 的利用情况，以及具体的process 的memory 数据等。 时间数据，即行为上的连续数据，比如某个Process 在一段时间内执行了哪些操作，某段时间内CPU 利用率的变化等。通常时空都是交融的，对应我们抓取资讯时往往也是。

2. 哪些数据可以用来分析.

Backtrace

Backtrace 又分成Java backtrace, Native Backtrace, Kernel Backtrace. 它是分析死机的非常重要的手段，我们可以快速的知道，对应的process/thread 在当时正在执行哪些动作，卡住哪里等。可以非常直观的分析死机现场。

另外还有一类trace 为ftrace/systrace, 除非特别开启, 以及在特定的流程点上添加, 这类trace 往往不是很详尽, 但也具有比较好的参考作用.

系统运行环境

客观的反应系统的执行环境，通常包括如CPU 利用率，Memory 使用情况， Storage 剩余情况等。这些资料也非常重要，比如可以快速的知道，当时是否有Process 在疯狂的执行，当时是不是处于严重的low memory 情况， Storage 是否有耗尽的情况发生等。

程序执行环境

客观的反应当时某个程序(Kernel 也可以看成一个程序)的执行现场, 此类资讯通常包括如process 的coredump, java heap prof, kernel 的memory dump 等。完整的执行环境，我们可以快速的知道当时具体的变量的值，寄存器值等，可以精细的分析问题。

其他的一些资讯

这些资讯相对来说，比较零散了，如通常的LOG, 一些debug 命令的结果, JTAG & CVD 的数据等。

四 、Backtrace 分析

1. Java Backtrace

从Java Backtrace, 我们可以知道当时Process 的虚拟机执行状态. Java Backtrace 依靠SignalCatcher 来抓取.
Google default: SignalCatcher catchs SIGQUIT(3), and then print the java backtrace to /data/anr/trace.txt
MTK Enhance: SignalCatcher catchs SIGSTKFLT(16), and then print the java backtrace to /data/anr/mtktrace.txt( 仅仅 Android ICS 4.0 <-> Android M 6.0版本)
You can update system properties dalvik.vm.stack-trace-file to Change the address, default is /data/anr/traces.txt

1.1 抓取的方式

在ENG Build 中

adb remount
adb shell chmod 0777 data/anr
adb shell kill -3 pid
adb pull /data/anr

在User Build 中

没有root 权限的情况下，只能直接pull 已经存在的backtrace.

adb pull /data/anr

你可以尝试直接使用下面的脚本一次性抓取

adb remount
adb shell chmod 0777 data/anr
adb shell ps
@echo off
set processid=
set /p processid=Please Input process id:
@echo on
adb shell kill -3 %processid%
@echo off
ping -n 8 127.0.0.1>nul
@echo on
adb pull data/anr/traces.txt trace-%processid%.txt
pause

1.2 JavaBacktrace 解析

Android 比较新的版本的java backtrace, 除了直接的thread backtrace 之外, 同时也会把ART 的一些基本状态也打印出来, 比较方便观察ART 的基本状态, 比如:

 ----- pid 1051 at 2018-09-29 23:23:52 -----
Cmd line: system_server
Build fingerprint: 'XXXXX/A73/A73:8.1.0/O11019/1537977601:user/release-keys'
ABI: 'arm64'
Build type: optimized
Zygote loaded classes=5413 post zygote classes=6049
Intern table: 61702 strong; 12632 weak
JNI: CheckJNI is off; globals=10050 (plus 1015 weak)
Libraries: /system/lib64/libandroid.so /system/lib64/libandroid_servers.so /system/lib64/libcompiler_rt.so /system/lib64/libdcfdecoderjni.so /system/lib64/libjavacrypto.so /system/lib64/libjnigraphics.so /system/lib64/libmedia_jni.so /system/lib64/libmediatek_exceptionlog.so /system/lib64/libperfframeinfo_jni.so /system/lib64/librutils.so /system/lib64/libsoundpool.so /system/lib64/libwebviewchromium_loader.so /system/lib64/libwifi-service.so /vendor/lib64/libnativecheck-jni.so libjavacore.so libopenjdk.so (17)
Heap: 9% free, 80MB/89MB; 1893251 objects
Dumping cumulative Gc timings
Start Dumping histograms for 12601 iterations for concurrent copying
ProcessMarkStack: Sum: 3760.617s 99% C.I. 35.990ms-1218.784ms Avg: 298.438ms Max: 14617.568ms
ScanImmuneSpaces: Sum: 216.241s 99% C.I. 2.719ms-110.340ms Avg: 17.160ms Max: 1644.161ms
FlipOtherThreads: Sum: 136.969s 99% C.I. 0.517ms-174.411ms Avg: 10.869ms Max: 5585.050ms
VisitConcurrentRoots: Sum: 119.937s 99% C.I. 1.928ms-50.934ms Avg: 9.518ms Max: 1356.509ms
ClearFromSpace: Sum: 66.775s 99% C.I. 0.168ms-21.473ms Avg: 5.299ms Max: 118.068ms
SweepSystemWeaks: Sum: 58.215s 99% C.I. 0.196ms-19.387ms Avg: 4.619ms Max: 342.553ms
GrayAllDirtyImmuneObjects: Sum: 57.570s 99% C.I. 0.133ms-123.041ms Avg: 4.568ms Max: 2010.547ms
ForwardSoftReferences: Sum: 37.474s 99% C.I. 0.037ms-13.834ms Avg: 2.973ms Max: 118.213ms
EnqueueFinalizerReferences: Sum: 30.905s 99% C.I. 0.094ms-22.239ms Avg: 2.452ms Max: 248.969ms
MarkingPhase: Sum: 24.277s 99% C.I. 0.257ms-51.155ms Avg: 1.926ms Max: 3743.053ms
VisitNonThreadRoots: Sum: 23.507s 99% C.I. 0.065ms-15.260ms Avg: 1.865ms Max: 190.694ms
ProcessReferences: Sum: 17.221s 99% C.I. 9.019us-4689.544us Avg: 683.321us Max: 94215us
EmptyRBMarkBitStack: Sum: 15.343s 99% C.I. 0.026ms-13.119ms Avg: 1.217ms Max: 145.672ms
ThreadListFlip: Sum: 10.730s 99% C.I. 128.387us-25549.046us Avg: 851.524us Max: 1555533us
InitializePhase: Sum: 7.689s 99% C.I. 125us-9536.627us Avg: 610.256us Max: 434902us
FlipThreadRoots: Sum: 4.346s 99% C.I. 16.387us-13773.217us Avg: 344.930us Max: 241943us
RecordFree: Sum: 4.106s 99% C.I. 95us-2474.875us Avg: 325.895us Max: 31656us
SweepAllocSpace: Sum: 2.746s 99% C.I. 32.035us-6375.082us Avg: 217.946us Max: 397272us
SweepLargeObjects: Sum: 2.611s 99% C.I. 10us-1976.352us Avg: 207.248us Max: 36205us
ResumeOtherThreads: Sum: 2.453s 99% C.I. 8.115us-8079.599us Avg: 194.712us Max: 86018us
ReclaimPhase: Sum: 2.086s 99% C.I. 9us-4266.285us Avg: 165.567us Max: 155093us
ResumeRunnableThreads: Sum: 1.759s 99% C.I. 8.063us-2676.218us Avg: 139.607us Max: 87029us
MarkStackAsLive: Sum: 782.752ms 99% C.I. 5us-799.362us Avg: 62.118us Max: 41297us
MarkZygoteLargeObjects: Sum: 741.028ms 99% C.I. 12us-899.899us Avg: 58.807us Max: 24679us
(Paused)GrayAllNewlyDirtyImmuneObjects: Sum: 651.153ms 99% C.I. 12us-373.754us Avg: 51.674us Max: 14328us
ClearRegionSpaceCards: Sum: 412.842ms 99% C.I. 8us-199.633us Avg: 32.762us Max: 16297us
(Paused)SetFromSpace: Sum: 357.553ms 99% C.I. 3us-286.340us Avg: 28.374us Max: 14500us
SwapBitmaps: Sum: 151.902ms 99% C.I. 4us-99.729us Avg: 12.054us Max: 5447us
Sweep: Sum: 110.635ms 99% C.I. 2us-49.924us Avg: 8.779us Max: 1087us
(Paused)FlipCallback: Sum: 105.455ms 99% C.I. 2us-99.800us Avg: 8.368us Max: 8433us
(Paused)ClearCards: Sum: 89.377ms 99% C.I. 1000ns-199016ns Avg: 295ns Max: 17545000ns
UnBindBitmaps: Sum: 17.838ms 99% C.I. 0.250us-49.765us Avg: 1.415us Max: 1516us
Done Dumping histograms
concurrent copying paused: Sum: 10.999s 99% C.I. 320.432us-63766.026us Avg: 872.888us Max: 1214342us
concurrent copying total time: 4607.007s mean time: 365.606ms
concurrent copying freed: 4075114399 objects with total size 152GB
concurrent copying throughput: 884547/s / 33MB/s
Cumulative bytes moved 115136403208
Cumulative objects moved 2160415247
Total time spent in GC: 4607.007s
Mean GC size throughput: 32MB/s
Mean GC object throughput: 884504 objects/s
Total number of allocations 4076810306
Total bytes allocated 145GB
Total bytes freed 145GB
Free memory 8MB
Free memory until GC 8MB
Free memory until OOME 431MB
Total memory 89MB
Max memory 512MB
Zygote space size 652KB
Total mutator paused time: 10.999s
Total time waiting for GC to complete: 71.458s
Total GC count: 12601
Total GC time: 4607.007s
Total blocking GC count: 3305
Total blocking GC time: 1302.402s
Histogram of GC count per 10000 ms: 0:11034,1:7128,2:1807,3:417,4:87,5:21,6:6,7:3,8:2,9:2,11:2,12:2,17:1
Histogram of blocking GC count per 10000 ms: 0:17706,1:2336,2:443,3:26,4:1
Registered native bytes allocated: 57354982
/system/framework/oat/arm64/com.android.location.provider.odex: speed
/system/priv-app/FusedLocation/oat/arm64/FusedLocation.odex: speed
/system/priv-app/Telecom/oat/arm64/Telecom.odex: speed
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/com.coloros.statistics.odex: quicken
/system/priv-app/SettingsProvider/oat/arm64/SettingsProvider.odex: speed
/system/framework/oat/arm64/services.odex: speed
/system/framework/oat/arm64/ethernet-service.odex: speed
/system/framework/oat/arm64/wifi-service.odex: speed
/system/framework/oat/arm64/com.android.location.provider.odex: speed
/system/framework/oat/arm64/mediatek-services.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/data/dalvik-cache/arm64/vendor@app@[e-mail]@classes.dex: quicken
/system/framework/oat/arm64/mediatek-framework-net.odex: quicken
/data/dalvik-cache/arm64/vendor@app@[e-mail]@classes.dex: quicken
Running non JIT

对于死机情况来说, 我们比较关注java heap 的memory 使用与GC 情况:

Heap: 9% free, 80MB/89MB; 1893251 objects 
Free memory 8MB
Free memory until GC 8MB
Free memory until OOME 431MB
Total memory 89MB
Max memory 512MB

==》 可以简单知道是否有java 层的object leaks, 以及触发GC 的情况

除去这些之后, 我们再来看java backtrace 的具体资讯.

下面是一小段system server 的java backtrace 的开始

----- pid 682 at 2014-07-30 1853 -----
Cmd line: system_server
JNI: CheckJNI is off; workarounds are off; pins=4; globals=1484 (plus 50 weak)
DALVIK THREADS:
(mutexes: tll=0 tsl=0 tscl=0 ghl=0)  <== 只有老版本有.
"main" prio=5 tid=1 NATIVE
  | group="main" sCount=1 dsCount=0 obj=0x4193fde0 self=0x418538f8
  | sysTid=682 nice=-2 sched=0/0 cgrp=apps handle=1074835940
  | state=S schedstat=( 47858718206 26265263191 44902 ) utm=4074 stm=711 core=0
  at android.os.MessageQueue.nativePollOnce(Native Method)
  at android.os.MessageQueue.next(MessageQueue.java:138)
  at android.os.Looper.loop(Looper.java:150)
  at com.android.server.ServerThread.initAndLoop(SystemServer.java:1468)
  at com.android.server.SystemServer.main(SystemServer.java:1563)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:515)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
  at dalvik.system.NativeStart.main(Native Method)

我们一行一行来解析.

0# 最开始是 -----PID at Time 然后接着 Cmd line: process name

1# the backtrace header: dvm thread ：“DALVIK THREADS:”
新版本中有包括 thread 量, 如: "DALVIK THREADS (214):" 可以观察到是否有java thread leaks.

2# Global DVM mutex value: if 0 unlock, else lock
tll: threadListLock,
tsl: threadSuspendLock,
tscl: threadSuspendCountLock
ghl: gcHeapLock

(mutexes: tll=0 tsl=0 tscl=0 ghl=0)

3# thread name, java thread Priority, [daemon], DVM thread id, DVM thread status.
"main" -> main thread -> activity thread
prio -> java thread priority default is 5, (nice =0, linux thread priority 120), domain is [1,10]
DVM thread id, NOT linux thread id
DVM thread Status:
ZOMBIE, RUNNABLE, TIMED_WAIT, MONITOR, WAIT, INITALIZING,STARTING, NATIVE, VMWAIT, SUSPENDED,UNKNOWN

"main" prio=5 tid=1 NATIVE

4# DVM thread status
group: default is “main”
Compiler,JDWP,Signal Catcher,GC,FinalizerWatchdogDaemon,FinalizerDaemon,ReferenceQueueDaemon are system group
sCount: thread suspend count
dsCount: thread dbg suspend count
obj: thread obj address
Sef: thread point address

group="main" sCount=1 dsCount=0 obj=0x4193fde0 self=0x418538f8

5 Linux thread status

sysTId: linux thread tid
Nice: linux thread nice value
sched: cgroup policy/gourp id
cgrp: c group
handle: handle address
sysTid=682 nice=-2 sched=0/0 cgrp=apps handle=1074835940

6 CPU Sched stat

Schedstat (Run CPU Clock/ns, Wait CPU Clock/ns, Slice times)
utm: utime, user space time(jiffies)
stm: stime, kernel space time(jiffies)
Core now running in cpu.
state=S schedstat=( 47858718206 26265263191 44902 ) utm=4074 stm=711 core=0

五、常见 Java backtrace 举例

1.ActivityThread 正常状态/ActivityThread Normal Case

Message Queue is empty, and thread wait for next message.
 "main" prio=5 tid=1 NATIVE
   | group="main" sCount=1 dsCount=0 obj=0x4193fde0 self=0x418538f8
   | sysTid=11559 nice=0 sched=0/0 cgrp=apps/bg_non_interactive handle=1074835940
   | state=S schedstat=( 2397315020 9177261498 7975 ) utm=100 stm=139 core=1
   at android.os.MessageQueue.nativePollOnce(Native Method)
   at android.os.MessageQueue.next(MessageQueue.java:138)
   at android.os.Looper.loop(Looper.java:150)
   at android.app.ActivityThread.main(ActivityThread.java:5299)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:515)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
   at dalvik.system.NativeStart.main(Native Method)

2.Java Backtrace Monitor case

Synchronized Lock： 等待同步锁时的backtrace.
 "AnrMonitorThread" prio=5 tid=24 MONITOR
   | group="main" sCount=1 dsCount=0 obj=0x41fd80c8 self=0x551ac808
   | sysTid=711 nice=0 sched=0/0 cgrp=apps handle=1356369328
   | state=S schedstat=( 8265377638 4744771625 6892 ) utm=160 stm=666 core=0
   at com.android.server.am.ANRManager$AnrDumpMgr.dumpAnrDebugInfoLocked(SourceFile:~832)
   - waiting to lock <0x42838968> (a com.android.server.am.ANRManager$AnrDumpRecord) held by tid=20 (ActivityManager)
   at com.android.server.am.ANRManager$AnrDumpMgr.dumpAnrDebugInfo(SourceFile:824)
   at com.android.server.am.ANRManager$AnrMonitorHandler.handleMessage(SourceFile:220)
   at android.os.Handler.dispatchMessage(Handler.java:110)
   at android.os.Looper.loop(Looper.java:193)
   at android.os.HandlerThread.run(HandlerThread.java:61)

3.执行JNI code 未返回，状态是native 的情况

 "WifiP2pService" prio=5 tid=37 NATIVE
   | group="main" sCount=1 dsCount=0 obj=0x427a9910 self=0x55f088d8
   | sysTid=734 nice=0 sched=0/0 cgrp=apps handle=1443230288
   | state=S schedstat=( 91121772 135245305 170 ) utm=7 stm=2 core=1
   #00  pc 00032700  /system/lib/libc.so (epoll_wait+12)
   #01  pc 000105e3  /system/lib/libutils.so (android::pollInner(int)+94)
   #02  pc 00010811  /system/lib/libutils.so (android::pollOnce(int, int*, int*, void**)+92)
   #03  pc 0006c96d  /system/lib/libandroid_runtime.so (android::pollOnce(_JNIEnv*, int)+22)
   #04  pc 0001eacc  /system/lib/libdvm.so (dvmPlatformInvoke+112)
   #05  pc 0004fed9  /system/lib/libdvm.so (dvmCallJNIMethod(unsigned int const*, JValue*, Method const*, Thread*)+484)
   #06  pc 00027ea8  /system/lib/libdvm.so
   #07  pc 0002f4b0  /system/lib/libdvm.so (dvmMterpStd(Thread*)+76)
   #08  pc 0002c994  /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JValue*)+188)
   #09  pc 000632a5  /system/lib/libdvm.so (dvmCallMethodV(Thread*, Method const*, Object*, bool, JValue*, std::__va_list)+340)
   #10  pc 000632c9  /system/lib/libdvm.so (dvmCallMethod(Thread*, Method const*, Object*, JValue*, ...)+20)
   #11  pc 00057961  /system/lib/libdvm.so
   #12  pc 0000dd40  /system/lib/libc.so (__thread_entry+72)
   at android.os.MessageQueue.nativePollOnce(Native Method)
   at android.os.MessageQueue.next(MessageQueue.java:138)
   at android.os.Looper.loop(Looper.java:150)
   at android.os.HandlerThread.run(HandlerThread.java:61)

4. 执行object.wait 等待状态

 "AsyncTask #1" prio=5 tid=33 WAIT
   | group="main" sCount=1 dsCount=0 obj=0x427a8480 self=0x56036b40
   | sysTid=733 nice=10 sched=0/0 cgrp=apps/bg_non_interactive handle=1443076000
   | state=S schedstat=( 1941480839 10140523154 4229 ) utm=119 stm=75 core=0
   at java.lang.Object.wait(Native Method)
   - waiting on <0x427a8618> (a java.lang.VMThread) held by tid=33 (AsyncTask #1)
   at java.lang.Thread.parkFor(Thread.java:1212)
   at sun.misc.Unsafe.park(Unsafe.java:325)
   at java.util.concurrent.locks.LockSupport.park(LockSupport.java:157)
   at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2017)
   at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:410)
   at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1035)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1097)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
   at java.lang.Thread.run(Thread.java:848)

5. Suspend 状态，通常表明是抓取backtrace 时，当时还正在执行java code, 被强制suspend 的情况

 "FileObserver" prio=5 tid=23 SUSPENDED
   | group="main" sCount=1 dsCount=0 obj=0x41fd1dc8 self=0x551abda0
   | sysTid=710 nice=0 sched=0/0 cgrp=apps handle=1427817920
   | state=S schedstat=( 130152222 399783851 383 ) utm=9 stm=4 core=0
   #00  pc 000329f8  /system/lib/libc.so (__futex_syscall3+8)
   #01  pc 000108cc  /system/lib/libc.so (__pthread_cond_timedwait_relative+48)
   #02  pc 0001092c  /system/lib/libc.so (__pthread_cond_timedwait+64)
   #03  pc 00055a93  /system/lib/libdvm.so
   #04  pc 0005614d  /system/lib/libdvm.so (dvmChangeStatus(Thread*, ThreadStatus)+34)
   #05  pc 0004ae7f  /system/lib/libdvm.so
   #06  pc 0004e353  /system/lib/libdvm.so
   #07  pc 000518d5  /system/lib/libandroid_runtime.so
   #08  pc 0008af9f  /system/lib/libandroid_runtime.so
   #09  pc 0001eacc  /system/lib/libdvm.so (dvmPlatformInvoke+112)
   #10  pc 0004fed9  /system/lib/libdvm.so (dvmCallJNIMethod(unsigned int const*, JValue*, Method const*, Thread*)+484)
   #11  pc 00027ea8  /system/lib/libdvm.so
   #12  pc 0002f4b0  /system/lib/libdvm.so (dvmMterpStd(Thread*)+76)
   #13  pc 0002c994  /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JValue*)+188)
   #14  pc 000632a5  /system/lib/libdvm.so (dvmCallMethodV(Thread*, Method const*, Object*, bool, JValue*, std::__va_list)+340)
   #15  pc 000632c9  /system/lib/libdvm.so (dvmCallMethod(Thread*, Method const*, Object*, JValue*, ...)+20)
   #16  pc 00057961  /system/lib/libdvm.so
   #17  pc 0000dd40  /system/lib/libc.so (__thread_entry+72)
   at android.os.FileObserver$ObserverThread.observe(Native Method)
   at android.os.FileObserver$ObserverThread.run(FileObserver.java:88)

六、Native Backtrace

1. Native Backtrace 抓取方式

1.利用debuggerd 抓取

MTK 已经制作了一个利用debuggerd 抓取Native backtrace 的tool RTT(Runtime Trace), 对应的执行命令是:

rtt built timestamp (Apr 18 2014 1521)
USAGE : rtt [-h] -f function -p pid [-t tid]
  -f funcion : current support functions:
                 bt  (Backtrace function)
  -p pid     : pid to trace
  -t tid     : tid to trace
  -n name    : process name to trace
  -h         : help menu

这个rtt 目前只有在eng/userdebug 中可以使用; 另外大家可以使用 google 默认的debuggerd 来抓取:

adb shell debuggerd -b pid

注意的是这些都是要依赖debuggerd 的流程正常, 以及对应抓取process 的debuggerd_signal_handler 行为正常, 否则抓取不到.

2. 添加代码直接抓取

Google 默认提供了CallStack API, 请参考

system/core/include/libutils/CallStack.h 
system/core/libutils/CallStack.cpp

可快速打印单个线程的backtrace.

2.解析Native Backtrace

你可以使用GDB, 或者addr2line 等 tool 来解析抓回的Native Backtrace, 从而知道当时正在执行的native 代码.
如addr2line 执行

arm-linux-androideabi-addr2line -f -C -e symbols address

七、Kernel Backtrace

1.Kernel Backtrace 抓取方式

1 运行时抓取

AEE/RTT 工具

Proc System

cat proc/pid/task/tid/stack

Sysrq-trigger

 adb shell cat proc/kmsg > kmsg.txt
 adb shell "echo 8 > proc/sys/kernel/printk“ //修改printk loglevel
 adb shell "echo t > /proc/sysrq-trigger“ //打印所有的backtrace
 adb shell "echo w > /proc/sysrq-trigger“//打印'-D' status 'D' 的 process

KDB

 Long press volume UP and DOWN more then 10s
 btp                             
 Display stack for process 
 bta             [DRSTCZEUIMA]        
 Display stack all processes
 btc                                  
 Backtrace current process on each cpu
 btt                           
 Backtrace process given its struct task add

2.添加代码直接抓取

  #include 
 当前thread:  dump_stack();
 其他thread:  show_stack(task, NULL);

3. Process/Thread 状态

"R (running)", /* 0/
"S (sleeping)", /1/
"D (disk sleep)", /2/
"T (stopped)", /4/
"t (tracing stop)", /8/
"Z (zombie)", /16/
"X (dead)", /32/
"x (dead)", /64/
"K (wakekill)", /128/
"W (waking)", /256 */

通常一般的Process 处于的状态都是S (sleeping), 而如果一旦发现处于如D (disk sleep), T (stopped), Z (zombie) 等就要认真审查.

八、几种典型的异常情况

1. Deadlock

下面这个case 可以看到PowerManagerService, ActivityManager, WindowManager 相互之间发生deadlock.

"PowerManagerService" prio=5 tid=25 MONITOR
  | group="main" sCount=1 dsCount=0 obj=0x42bae270 self=0x6525d5c0
  | sysTid=913 nice=0 sched=0/0 cgrp=apps handle=1696964440
  | state=S schedstat=( 5088939411 10237027338 34016 ) utm=232 stm=276 core=2
  at com.android.server.am.ActivityManagerService.bindService(ActivityManagerService.java:~14079)
  - waiting to lock <0x42aa0f78> (a com.android.server.am.ActivityManagerService) held by tid=16 (ActivityManager)
  at android.app.ContextImpl.bindServiceCommon(ContextImpl.java:1665)
  at android.app.ContextImpl.bindService(ContextImpl.java:1648)
  at com.android.server.power.PowerManagerService.bindSmartStandByService(PowerManagerService.java:4090)
  at com.android.server.power.PowerManagerService.handleSmartStandBySettingChangedLocked(PowerManagerService.java:4144)
  at com.android.server.power.PowerManagerService.access$5600(PowerManagerService.java:102)
  at com.android.server.power.PowerManagerService$SmartStandBySettingObserver.onChange(PowerManagerService.java:4132)
  at android.database.ContentObserver$NotificationRunnable.run(ContentObserver.java:181)
  at android.os.Handler.handleCallback(Handler.java:809)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:139)
  at android.os.HandlerThread.run(HandlerThread.java:58)
  
  "ActivityManager" prio=5 tid=16 MONITOR
  | group="main" sCount=1 dsCount=0 obj=0x42aa0d08 self=0x649166b0
  | sysTid=902 nice=-2 sched=0/0 cgrp=apps handle=1687251744
  | state=S schedstat=( 39360881460 25703061063 69675 ) utm=1544 stm=2392 core=2
  at com.android.server.wm.WindowManagerService.setAppVisibility(WindowManagerService.java:~4783)
  - waiting to lock <0x42d17590> (a java.util.HashMap) held by tid=12 (WindowManager)
  at com.android.server.am.ActivityStack.stopActivityLocked(ActivityStack.java:2432)
  at com.android.server.am.ActivityStackSupervisor.activityIdleInternalLocked(ActivityStackSupervisor.java:2103)
  at com.android.server.am.ActivityStackSupervisor$ActivityStackSupervisorHandler.activityIdleInternal(ActivityStackSupervisor.java:2914)
  at com.android.server.am.ActivityStackSupervisor$ActivityStackSupervisorHandler.handleMessage(ActivityStackSupervisor.java:2921)
  at android.os.Handler.dispatchMessage(Handler.java:110)
  at android.os.Looper.loop(Looper.java:147)
  at com.android.server.am.ActivityManagerService$AThread.run(ActivityManagerService.java:2112)
  
  "WindowManager" prio=5 tid=12 MONITOR
  | group="main" sCount=1 dsCount=0 obj=0x42a92550 self=0x6491dd48
  | sysTid=898 nice=-4 sched=0/0 cgrp=apps handle=1687201104
  | state=S schedstat=( 60734070955 41987172579 219755 ) utm=4659 stm=1414 core=1
  at com.android.server.power.PowerManagerService.setScreenBrightnessOverrideFromWindowManagerInternal(PowerManagerService.java:~3207)
  - waiting to lock <0x42a95140> (a java.lang.Object) held by tid=25 (PowerManagerService)
  at com.android.server.power.PowerManagerService.setScreenBrightnessOverrideFromWindowManager(PowerManagerService.java:3196)
  at com.android.server.wm.WindowManagerService.performLayoutAndPlaceSurfacesLockedInner(WindowManagerService.java:9686)
  at com.android.server.wm.WindowManagerService.performLayoutAndPlaceSurfacesLockedLoop(WindowManagerService.java:8923)
  at com.android.server.wm.WindowManagerService.performLayoutAndPlaceSurfacesLocked(WindowManagerService.java:8879)
  at com.android.server.wm.WindowManagerService.access$500(WindowManagerService.java:170)
  at com.android.server.wm.WindowManagerService$H.handleMessage(WindowManagerService.java:7795)
  at android.os.Handler.dispatchMessage(Handler.java:110)
  at android.os.Looper.loop(Looper.java:147)
  at android.os.HandlerThread.run(HandlerThread.java:58)

2. 执行JNI native code 后一去不复返

"main" prio=5 tid=1 NATIVE
  | group="main" sCount=1 dsCount=0 obj=0x41bb3d98 self=0x41ba2878
  | sysTid=814 nice=-2 sched=0/0 cgrp=apps handle=1074389380
  | state=D schedstat=( 22048890928 19526803112 32612 ) utm=1670 stm=534 core=0
  (native backtrace unavailable)
  at android.hardware.SystemSensorManager$BaseEventQueue.nativeDisableSensor(Native Method)
  at android.hardware.SystemSensorManager$BaseEventQueue.disableSensor(SystemSensorManager.java:399)
  at android.hardware.SystemSensorManager$BaseEventQueue.removeAllSensors(SystemSensorManager.java:325)
  at android.hardware.SystemSensorManager.unregisterListenerImpl(SystemSensorManager.java:194)
  at android.hardware.SensorManager.unregisterListener(SensorManager.java:560)
  at com.android.internal.policy.impl.WindowOrientationListener.disable(WindowOrientationListener.java:139)
  at com.android.internal.policy.impl.PhoneWindowManager.updateOrientationListenerLp(PhoneWindowManager.java:774)
  at com.android.internal.policy.impl.PhoneWindowManager.screenTurnedOff(PhoneWindowManager.java:4897)
  at com.android.server.power.Notifier.sendGoToSleepBroadcast(Notifier.java:518)
  at com.android.server.power.Notifier.sendNextBroadcast(Notifier.java:434)
  at com.android.server.power.Notifier.access$500(Notifier.java:63)
  at com.android.server.power.Notifier$NotifierHandler.handleMessage(Notifier.java:584)
  at android.os.Handler.dispatchMessage(Handler.java:110)
  at android.os.Looper.loop(Looper.java:193)
  at com.android.server.ServerThread.initAndLoop(SystemServer.java:1436)
  at com.android.server.SystemServer.main(SystemServer.java:1531)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:515)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
  at dalvik.system.NativeStart.main(Native Method)

===>
KERNEL SPACE BACKTRACE, sysTid=814

 [] 0xffffffff from [] __schedule+0x3fc/0x950
 [] __schedule+0xc/0x950 from [] schedule+0x40/0x80
 [] schedule+0xc/0x80 from [] schedule_preempt_disabled+0x20/0x2c
 [] schedule_preempt_disabled+0xc/0x2c from [] mutex_lock_nested+0x1b8/0x560
 [] mutex_lock_nested+0xc/0x560 from [] gsensor_operate+0x1bc/0x2c0
 [] gsensor_operate+0xc/0x2c0 from [] hwmsen_enable+0xa8/0x30c
 [] hwmsen_enable+0xc/0x30c from [] hwmsen_unlocked_ioctl+0x2fc/0x528
 [] hwmsen_unlocked_ioctl+0xc/0x528 from [] do_vfs_ioctl+0x94/0x5bc
 [] do_vfs_ioctl+0xc/0x5bc from [] sys_ioctl+0x7c/0x8c
 [] sys_ioctl+0xc/0x8c from [] ret_fast_syscall+0x0/0x40
 []  from []
编辑：黄飞