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Still Deadlocked

March 11th, 2012

Wow… three months since my last post about my Android Clock Widget Project. While I’ve failed to bring stability to the clock selector during that time, I have figured out that the problem is not actually due to a deadlock. Instead, it appears that my project is tickling a bug in the Dalvik VM’s garbage collector.

Depending on the device and operating system level, there are subtle changes in behavior. In most cases, there is a crash log written to the /data/tombstones folder. The most revealing tombstone file has come from a Samsung Captivate running a version of the AOKP ICS ROM.

Build fingerprint: 'samsung/SGH-I897/SGH-I897:2.3.5/GINGERBREAD/UCKK4:user/release-keys'
pid: 1758, tid: 1777  >>> com.seterasoft.mclock <<<
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr deadbaad
 r0 deadbaad  r1 00000001  r2 40000000  r3 00000000
 r4 00000000  r5 00000027  r6 50c53b40  r7 00000064
 r8 41338018  r9 00000024  10 50c53a6c  fp 50c53ab0
 ip ffffffff  sp 50c53a30  lr 400fdf79  pc 400fa694  cpsr 60000030
 d0  0000000000000000  d1  0000000000000000
 d2  0000000000000000  d3  0000000000000000
 d4  0000000000000000  d5  0000000000000000
 d6  0000000000000000  d7  0000000000000000
 d8  0000000000000000  d9  0000000000000000
 d10 0000000000000000  d11 0000000000000000
 d12 0000000000000000  d13 0000000000000000
 d14 0000000000000000  d15 0000000000000000
 d16 0000000000000000  d17 0000000000000000
 d18 0000000000000000  d19 0000000000000000
 d20 0000000000000000  d21 0000000000000000
 d22 0000000000000000  d23 0000000000000000
 d24 0000000000000000  d25 0000000000000000
 d26 0000000000000000  d27 0000000000000000
 d28 0100010001000100  d29 0100010001000100
 d30 0000000000000000  d31 3ff0000000000000
 scr 2800001b

         #00  pc 00017694  /system/lib/libc.so
         #01  pc 00007bb0  /system/lib/libcutils.so (mspace_merge_objects)
         #02  pc 0007b6c8  /system/lib/libdvm.so (_Z21dvmHeapSourceFreeListjPPv)
         #03  pc 00042ce0  /system/lib/libdvm.so
         #04  pc 00032f94  /system/lib/libdvm.so (_Z22dvmHeapBitmapSweepWalkPK10HeapBitmapS1_jjPFvjPPvS2_ES2_)
         #05  pc 00042c9c  /system/lib/libdvm.so (_Z27dvmHeapSweepUnmarkedObjectsbbPjS_)
         #06  pc 000337c0  /system/lib/libdvm.so (_Z25dvmCollectGarbageInternalPK6GcSpec)
         #07  pc 0005ff6c  /system/lib/libdvm.so (_Z17dvmCollectGarbagev)
         #08  pc 00072a8e  /system/lib/libdvm.so
         #09  pc 00030a8c  /system/lib/libdvm.so
         #10  pc 00034248  /system/lib/libdvm.so (_Z12dvmInterpretP6ThreadPK6MethodP6JValue)
         #11  pc 0006c692  /system/lib/libdvm.so (_Z14dvmCallMethodVP6ThreadPK6MethodP6ObjectbP6JValueSt9__va_list)
         #12  pc 0006c6b4  /system/lib/libdvm.so (_Z13dvmCallMethodP6ThreadPK6MethodP6ObjectP6JValuez)
         #13  pc 0005f7c0  /system/lib/libdvm.so
         #14  pc 00012c14  /system/lib/libc.so (__thread_entry)
         #15  pc 00012744  /system/lib/libc.so (pthread_create)

The failing function appears to be implemented in dlmalloc.c in the Android source, but I really don't have any good idea about what might be causing the crash. I also don't appear to be the only one, as there are other references on the web that look similar.

To this point, I've tried a variety of things to try to track down the problem. I've gone so far as to try to build my own version of the Cyanogenmod with the idea that I might be able to add more logging output. So far, I've not had any luck with this approach. I generally have no problem walking away from hobby projects when I lose interest. However, this has turned into a competition of me versus the computer and I'm not quite ready to give up.

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