Bug 28331 - Multi-threaded exec pthread_create and dlopen may cause deadlock
Summary: Multi-threaded exec pthread_create and dlopen may cause deadlock
Alias: None
Product: glibc
Classification: Unclassified
Component: dynamic-link (show other bugs)
Version: 2.35
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
Depends on:
Reported: 2021-09-11 10:35 UTC by xujing
Modified: 2021-09-13 07:26 UTC (History)
1 user (show)

See Also:
Last reconfirmed:


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Description xujing 2021-09-11 10:35:42 UTC
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)
Comment 1 xujing 2021-09-13 02:59:13 UTC
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 ()