bionic: fix atfork hanlder_mutex deadlock
After applying the kernel_id fix, the system refused to boot up and we
got following crash log:
I/DEBUG ( 113): pid: 618, tid: 618 >>> org.simalliance.openmobileapi.service:remote <<<
I/DEBUG ( 113): signal 16 (SIGSTKFLT), code -6 (?), fault addr --------
I/DEBUG ( 113): eax fffffe00 ebx b77de994 ecx 00000080 edx 00724002
I/DEBUG ( 113): esi 00000000 edi 00004000
I/DEBUG ( 113): xcs 00000073 xds 0000007b xes 0000007b xfs 00000000 xss 0000007b
I/DEBUG ( 113): eip b7761351 ebp bfdf3de8 esp bfdf3dc4 flags 00000202
I/DEBUG ( 113): #00 eip: 00015351 /system/lib/libc.so
I/DEBUG ( 113): #01 eip: 0000d13c /system/lib/libc.so (pthread_mutex_lock)
I/DEBUG ( 113): #02 eip: 00077b48 /system/lib/libc.so (__bionic_atfork_run_prepare)
I/DEBUG ( 113): #03 eip: 00052cdb /system/lib/libc.so (fork)
I/DEBUG ( 113): #04 eip: 0009ae91 /system/lib/libdvm.so (_Z18dvmOptimizeDexFileillPKcjjb)
I/DEBUG ( 113): #05 eip: 000819d6 /system/lib/libdvm.so (_Z14dvmJarFileOpenPKcS0_PP7JarFileb)
I/DEBUG ( 113): #06 eip: 000b175e /system/lib/libdvm.so (_ZL40Dalvik_dalvik_system_DexFile_openDexFilePKjP6JValue)
I/DEBUG ( 113): #07 eip: 0011fb94 /system/lib/libdvm.so
Root cause:
The atfork uses the mutex handler_mutex to protect the atfork_head. The
parent will call __bionic_atfork_run_prepare() to lock the handler_mutex,
and need both the parent and child to unlock their own copy of handler_mutex
after fork. At that time, the owner of hanlder_mutex is set as the parent.
If we apply the kernel_id fix, then the child's kernel_id will be set as
child's tid.
The handler_mutex is a recursive lock, and pthread_mutex_unlock(&hander_mutex)
will fail because the mutex owner is the parent, while the current tid
(__get_thread()->kernel_id) is child, not matched with the mutex owner.
At that time, the handler_mutex is left in lock state.If the child wants to
fork other process after than, then it will try to lock handler_mutex, and
then be deadlocked.
Fix:
Since the child has its own copy of vm space from the the parent, the
child space's handler_mutex should be reset to the initialized state.
Change-Id: I3907dd9a153418fb78862f2aa6d0302c375d9e27
Signed-off-by: Jack Ren <jack.ren@intel.com>
Signed-off-by: Chenyang Du <chenyang.du@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
1 file changed
