Android dalvik garbage collection may crash?

Question

We're working on a project for Android jelly bean. Our platform is arm-based, and the kernel version is 3.1.10. In our development process, we found that there is very low probability that the application crash happened in dalvik. Based on the following backtrace log, the crash appeared during garbage collection function. After using addr2line to analyze the pc address, we found the obj->clazz became a violate address when the issue has happened.

The code flow is: (dvmHeapScanMarkedObjects -> processMarkStack-> scanObject->(IS_CLASS_FLAG_SET(obj->clazz,CLASS_ISARRAY)))

Now we are stuck here and can’t find a way to solve it. So we need more suggestion and help.

Does anyone know this issue or how to keep checking on it?

The backtrace log as below:

F/libc    (  912): Fatal signal 11 (SIGSEGV) at 0x00000025 (code=1), thread 912 (zygote)
I/DEBUG   (  910): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***I/DEBUG   (  910): Revision: '32'
I/DEBUG   (  910): pid: 912, tid: 912, name: zygote  >>> zygote <<<
I/DEBUG   (  910): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 00000025
I/DEBUG   (  910):     r0 00000005  r1 41246df0  r2 44208890  r3 412471e8
I/DEBUG   (  910):     r4 40e3c1b8  r5 412569c0  r6 40e3c1b8  r7 41246df0
I/DEBUG   (  910):     r8 0000154c  r9 00000000  sl 000798e4  fp 7fffffff
I/DEBUG   (  910):     ip 51b2c044  sp bee580c0  lr 40dc5b88  pc 40dc598c  cpsr 80000010
I/DEBUG   (  910):     d0  6e69737275636567  d1  6f7268540000fa2e
I/DEBUG   (  910):     d2  573752085737512e  d3  573752785737522e
I/DEBUG   (  910):     d4  5737527857375240  d5  573841a0573752b0
I/DEBUG   (  910):     d6  00010000573841d8  d7  000000614ac3ff00
I/DEBUG   (  910):     d8  0000000000000000  d9  0000000000000000
I/DEBUG   (  910):     d10 0000000000000000  d11 0000000000000000
I/DEBUG   (  910):     d12 0000000000000000  d13 0000000000000000
I/DEBUG   (  910):     d14 0000000000000000  d15 0000000000000000
I/DEBUG   (  910):     d16 0000000000019a5c  d17 0000000000019a5c
I/DEBUG   (  910):     d18 0000000000000000  d19 3fe8000000000000
I/DEBUG   (  910):     d20 0000000000000000  d21 0000000000000000
I/DEBUG   (  910):     d22 0000000000000000  d23 0000000000000000
I/DEBUG   (  910):     d24 0000000000000000  d25 0000000000000000
I/DEBUG   (  910):     d26 0000000000000000  d27 0000000000000000
I/DEBUG   (  910):     d28 0000000000000000  d29 0000000000000000
I/DEBUG   (  910):     d30 0000000000000000  d31 0000000000000000
I/DEBUG   (  910):     scr 60000010
I/DEBUG   (  910):
I/DEBUG   (  910): backtrace:
I/DEBUG   (  910):     #00  pc 0003798c  /system/lib/libdvm.so
I/DEBUG   (  910):     #01  pc 00037b84  /system/lib/libdvm.so
I/DEBUG   (  910):     #02  pc 000298c0  /system/lib/libdvm.so (dvmCollectGarbageInternal(GcSpec const*)+196)
I/DEBUG   (  910):     #03  pc 0002a0bc  /system/lib/libdvm.so (dvmMalloc(unsigned int, int)+152)
I/DEBUG   (  910):     #04  pc 00054f57  /system/lib/libdvm.so (dvmAllocObject+6)
I/DEBUG   (  910):     #05  pc 0001ecb0  /system/lib/libdvm.so
I/DEBUG   (  910):     #06  pc 0002b754  /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JValue*)+184)
I/DEBUG   (  910):     #07  pc 0005fe09  /system/lib/libdvm.so (dvmCallMethodV(Thread*, Method const*, Object*, bool, JValue*, std::__va_list)+272)
I/DEBUG   (  910):     #08  pc 0005fe33  /system/lib/libdvm.so (dvmCallMethod(Thread*, Method const*, Object*, JValue*, ...)+20)
I/DEBUG   (  910):     #09  pc 000539c9  /system/lib/libdvm.so (dvmPrepMainThread()+188)
I/DEBUG   (  910):     #10  pc 00047c65  /system/lib/libdvm.so (dvmStartup(int, char const* const*, bool, _JNIEnv*)+1108)
I/DEBUG   (  910):     #11  pc 0004dd8d  /system/lib/libdvm.so (JNI_CreateJavaVM+544)
I/DEBUG   (  910):     #12  pc 00047227  /system/lib/libandroid_runtime.so (android::AndroidRuntime::startVm(_JavaVM**, _JNIEnv**)+1626)
I/DEBUG   (  910):     #13  pc 000476bd  /system/lib/libandroid_runtime.so (android::AndroidRuntime::start(char const*, char const*)+176)
I/DEBUG   (  910):     #14  pc 00000db7  /system/bin/app_process
I/DEBUG   (  910):
I/DEBUG   (  910): stack:
I/DEBUG   (  910):          bee58080  00000000
I/DEBUG   (  910):          bee58084  40dc599c  /system/lib/libdvm.so
I/DEBUG   (  910):          bee58088  41247f38  /dev/ashmem/dalvik-heap (deleted)
I/DEBUG   (  910):          bee5808c  000003f0
I/DEBUG   (  910):          bee58090  000000fd
I/DEBUG   (  910):          bee58094  00000000
I/DEBUG   (  910):          bee58098  41246ebc  [heap]
I/DEBUG   (  910):          bee5809c  40db7578  /system/lib/libdvm.so (dvmHeapBitmapScanWalk(HeapBitmap*, void (*)(Object*, void*, void*), void*)+128)
I/DEBUG   (  910):          bee580a0  40dc5b9c  /system/lib/libdvm.so
I/DEBUG   (  910):          bee580a4  41247f38  /dev/ashmem/dalvik-heap (deleted)
I/DEBUG   (  910):          bee580a8  40e3c1b8  /system/lib/libdvm.so
I/DEBUG   (  910):          bee580ac  412569a0  /dev/ashmem/dalvik-heap (deleted)
I/DEBUG   (  910):          bee580b0  40e3c1b8  /system/lib/libdvm.so
I/DEBUG   (  910):          bee580b4  41246df0  [heap]
I/DEBUG   (  910):          bee580b8  df0027ad
I/DEBUG   (  910):          bee580bc  00000000
I/DEBUG   (  910):     #00  bee580c0  51b2c048  /dev/ashmem/dalvik-mark-stack (deleted)
I/DEBUG   (  910):          bee580c4  41246df0  [heap]
I/DEBUG   (  910):          bee580c8  41246dd8  [heap]
I/DEBUG   (  910):          bee580cc  40e3c1b8  /system/lib/libdvm.so
I/DEBUG   (  910):          bee580d0  00000001
I/DEBUG   (  910):          bee580d4  40dc5b88  /system/lib/libdvm.so
I/DEBUG   (  910):     #01  bee580d8  40e34aa8  /system/lib/libdvm.so
I/DEBUG   (  910):          bee580dc  40db78c4  /system/lib/libdvm.so (dvmCollectGarbageInternal(GcSpec const*)+200)
I/DEBUG   (  910):     #02  bee580e0  bee58124  [stack]
I/DEBUG   (  910):          bee580e4  40df9095  /system/lib/libdvm.so
I/DEBUG   (  910):          bee580e8  5855879e  /data/dalvik-cache/system@[email protected]@classes.dex
I/DEBUG   (  910):          bee580ec  40087010
I/DEBUG   (  910):          bee580f0  5855879e  /data/dalvik-cache/system@[email protected]@classes.dex
I/DEBUG   (  910):          bee580f4  410be000  /dev/ashmem/dalvik-aux-structure (deleted)
I/DEBUG   (  910):          bee580f8  00000000
I/DEBUG   (  910):          bee580fc  00000000
I/DEBUG   (  910):          bee58100  000006db
I/DEBUG   (  910):          bee58104  410be000  /dev/ashmem/dalvik-aux-structure (deleted)
I/DEBUG   (  910):          bee58108  00000000
I/DEBUG   (  910):          bee5810c  410f55cc  /dev/ashmem/dalvik-aux-structure (deleted)
I/DEBUG   (  910):          bee58110  412569d8  /dev/ashmem/dalvik-heap (deleted)
I/DEBUG   (  910):          bee58114  41248338  /dev/ashmem/dalvik-heap (deleted)
I/DEBUG   (  910):          bee58118  41248338  /dev/ashmem/dalvik-heap (deleted)
I/DEBUG   (  910):          bee5811c  40e3c1b8  /system/lib/libdvm.so
I/DEBUG   (  910):          ........  ........

Answer 1

Ah it took me quite a long time to analyse the situation for me with a similar issue. Hope my analysis help you .

With my issue , the problem is because of Memory reordering by compiler . In dalvik several threads share common memory ASHMEM . This ASHMEM might have been corrupted because of memory re-ordering by compiler for optimisation . To avoid memory reordering at particular point execute memory barrier (AKA membar) .Check this link for executing membar

Just put a memory barrier ANDROID_MEMBAR_BARRIER() before object allocation and object freeing in Garbage-collecting memory allocator(like dalvik/vm/alloc/alloc.cpp) and in class.cpp , array.cpp and proxy.cpp in dalvik directory of android source code . This should solve the issue.

For more infomation on Memory barrier pls check following links

memory barrier

example

white paper on Hardware View of Memory Barriers