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bionic: fix atfork hanlder_mutex deadlock

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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>
This commit is contained in:
Jack Ren 2012-03-16 16:37:35 +08:00
parent 73b5cad989
commit 34e89c232d
1 changed files with 4 additions and 1 deletions
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5
libc/bionic/pthread-atfork.c
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@ -74,6 +74,7 @@ void __bionic_atfork_run_prepare()
void __bionic_atfork_run_child()
{
struct atfork_t *cursor;
pthread_mutexattr_t attr;
/* Call pthread_atfork() child handlers */
for (cursor = atfork_head.cqh_first;
@ -84,7 +85,9 @@ void __bionic_atfork_run_child()
}
}
pthread_mutex_unlock(&handler_mutex);
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&handler_mutex, &attr);
}
void __bionic_atfork_run_parent()