I recently written a signal handler which uses backtrace from execinfo.h and it is working fine on MacOs but when it is used on Linux (Ubuntu Debian) it is waiting for lock indefinetly. Not sure if this helps but my multi-threaded program ( pthread) uses rocksdb to store data and I intentionally kept a segfault in rocksdb so that I can test my signal handler if any issue occurs at rocksdb end but I am not able debug why lock is waiting.