tsan: False positive for lock-order inversion due to two locks mapped to the same address.

[nanlour]

It seems that if two locks are mapped to the same address, the sanitizer considers them as the same lock. Here is an example code that triggers this warning:

#include <mutex>                                                                                                        

std::mutex m1;

void foo(bool ok) {
    std::mutex m2;
    std::unique_lock l1(m1, std::defer_lock);
    if(!ok) l1.lock();
    std::unique_lock l2(m2);
    if (ok) l1.lock();
}
                                                                                                                    
int main()                                                                                                              
{                                                                                                                                                                                                        
    foo(false);
    foo(true);
    return 0;                                                                                                          
}

Building and running it produces the following output:

==================
WARNING: ThreadSanitizer: lock-order-inversion (potential deadlock) (pid=81574)
  Cycle in lock order graph: M0 (0x560a6196cae8) => M1 (0x7ffef6323e90) => M0

  Mutex M1 acquired here while holding mutex M0 in main thread:
    #0 pthread_mutex_lock <null> (main+0x6227e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #1 __gthread_mutex_lock(pthread_mutex_t*) /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/x86_64-linux-gnu/c++/14/bits/gthr-default.h:762:14 (main+0xe0df3) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #2 std::mutex::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/std_mutex.h:113:17 (main+0xe1275) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #3 std::unique_lock<std::mutex>::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/unique_lock.h:147:17 (main+0xe0f55) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #4 std::unique_lock<std::mutex>::unique_lock(std::mutex&) /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/unique_lock.h:73:2 (main+0xe0ffe) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #5 foo(bool) /threadSemtizer/main.cpp:9:22 (main+0xe0c65) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #6 main /threadSemtizer/main.cpp:15:5 (main+0xe0d0e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)

  Mutex M0 previously acquired by the same thread here:
    #0 pthread_mutex_lock <null> (main+0x6227e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #1 __gthread_mutex_lock(pthread_mutex_t*) /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/x86_64-linux-gnu/c++/14/bits/gthr-default.h:762:14 (main+0xe0df3) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #2 std::mutex::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/std_mutex.h:113:17 (main+0xe1275) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #3 std::unique_lock<std::mutex>::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/unique_lock.h:147:17 (main+0xe0f55) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #4 foo(bool) /threadSemtizer/main.cpp:8:16 (main+0xe0c3d) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #5 main /threadSemtizer/main.cpp:15:5 (main+0xe0d0e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)

  Mutex M0 acquired here while holding mutex M1 in main thread:
    #0 pthread_mutex_lock <null> (main+0x6227e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #1 __gthread_mutex_lock(pthread_mutex_t*) /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/x86_64-linux-gnu/c++/14/bits/gthr-default.h:762:14 (main+0xe0df3) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #2 std::mutex::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/std_mutex.h:113:17 (main+0xe1275) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #3 std::unique_lock<std::mutex>::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/unique_lock.h:147:17 (main+0xe0f55) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #4 foo(bool) /threadSemtizer/main.cpp:10:16 (main+0xe0c7d) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #5 main /threadSemtizer/main.cpp:16:5 (main+0xe0d1d) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)

  Mutex M1 previously acquired by the same thread here:
    #0 pthread_mutex_lock <null> (main+0x6227e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #1 __gthread_mutex_lock(pthread_mutex_t*) /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/x86_64-linux-gnu/c++/14/bits/gthr-default.h:762:14 (main+0xe0df3) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #2 std::mutex::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/std_mutex.h:113:17 (main+0xe1275) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #3 std::unique_lock<std::mutex>::lock() /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/unique_lock.h:147:17 (main+0xe0f55) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #4 std::unique_lock<std::mutex>::unique_lock(std::mutex&) /usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/unique_lock.h:73:2 (main+0xe0ffe) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #5 foo(bool) /threadSemtizer/main.cpp:9:22 (main+0xe0c65) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)
    #6 main /threadSemtizer/main.cpp:16:5 (main+0xe0d1d) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a)

SUMMARY: ThreadSanitizer: lock-order-inversion (potential deadlock) (/threadSemtizer/main+0x6227e) (BuildId: aab00fd10cf0f00c10ca928364603028f30e183a) in pthread_mutex_lock
==================