after merge commit 1387ad6225c2222f027790e3f460e31aa5dd2c54, multi-threaded exec pthread_create and dlopen may cause deadlock. thread1：dlopen hold dl_load_lock and then load a dynamic library which will hold ACE_lock(defined by my self) thread2：a program hold ACE_lock and then call pthread_create=>_dl_allocate_tls_init will hold dlopen dl_load_lock in this case, it will cause deadlock. for example: thread1：dlopen => hold dl_load_lock => spawn_n => wait for hold ACE_lock thread2：spawn_n => hold ACE_lock => pthread_create => _dl_allocate_tls_init => wait for hold dl_load_lock (spawn_n is my own function)
If I have a c++ dynamic library(named libA.so) that contains a global object, the global object will call the post-constructor at initialization and hold it's own lock(named A_lock) when dlopen loads libA.so. Assume that two threads execute the following process： Thread1:dlopen(libA.so) => hold dl_load_lock => load libA.so => init global object from libA.so => wait for hold A_lock Thread2:my own code hold A_lock => pthread_create => _dl_allocate_tls_init => wait for hold dl_load_lock In this case, an ABBA deadlock occurs. Is this a bug? My stack looks like this: Thread 1 (LWP 136013): #0 0x00007f57a108510d in ?? () from /usr/lib64/libpthread.so.0 #1 0x00007f57a107e4d1 in pthread_mutex_lock () from /usr/lib64/libpthread.so.0 #1 stack waiting for holding A_lock ... #6 0x00007f5781c1bb8b in LogProcess::Init (strProcName=..., nProcHandle=nProcHandle@entry=0) at ./service/biz_frame/code/server/src/logging/logprocess.cpp:107 ... #20 0x00007f57a0fef21f in _dl_catch_exception () from /usr/lib64/libc.so.6 #21 0x00007f57a786442b in ?? () from /lib64/ld-linux-x86-64.so.2 #22 0x00007f57a3de2296 in ?? () from /usr/lib64/libdl.so.2 #23 0x00007f57a0fef21f in _dl_catch_exception () from /usr/lib64/libc.so.6 #24 0x00007f57a0fef2af in _dl_catch_error () from /usr/lib64/libc.so.6 #25 0x00007f57a3de2985 in ?? () from /usr/lib64/libdl.so.2 #26 0x00007f57a3de2351 in dlopen () from /usr/lib64/libdl.so.2 ... ... #38 0x00007f57a0fb3520 in clone () from /usr/lib64/libc.so.6 Thread 2 (LWP 134627): #0 0x00007f57a108510d in ?? () from /usr/lib64/libpthread.so.0 #1 0x00007f57a107e580 in pthread_mutex_lock () from /usr/lib64/libpthread.so.0 #2 0x00007f57a7863835 in _dl_allocate_tls_init () from /lib64/ld-linux-x86-64.so.2 #3 0x00007f57a107cb7c in pthread_create () from /usr/lib64/libpthread.so.0 ... #10 Stack holding A_lock ... #14 0x0000561689e0d579 in main ()