==22308== Thread 4:
==22308== Conflicting load by thread 4 at 0x0823a530 size 4
==22308==    at 0x4C337E2: pthread_mutex_lock (in /usr/lib/valgrind/vgpreload_drd-amd64-linux.so)
==22308==    by 0x8034486: _nss_files_gethostbyname3_r (files-hosts.c:127)
==22308==    by 0x8034BC3: _nss_files_gethostbyname2_r (files-hosts.c:372)
==22308==    by 0x5172568: gethostbyname2_r@@GLIBC_2.2.5 (getXXbyYY_r.c:266)
==22308==    by 0x5132226: gaih_inet (getaddrinfo.c:586)
==22308==    by 0x5134E0C: getaddrinfo (getaddrinfo.c:2406)
==22308==    by 0x40096F: doit (k.c:39)
==22308==    by 0x4C30E7B: ??? (in /usr/lib/valgrind/vgpreload_drd-amd64-linux.so)
==22308==    by 0x4E4F181: start_thread (pthread_create.c:312)
==22308==    by 0x515F47C: clone (clone.S:111)
==22308== Location 0x823a530 is 16 bytes inside global var "lock"
==22308== declared at files-XXX.c:61
==22308== Other segment start (thread 3)
==22308==    at 0x4C34544: pthread_mutex_unlock (in /usr/lib/valgrind/vgpreload_drd-amd64-linux.so)
==22308==    by 0x4C30E75: ??? (in /usr/lib/valgrind/vgpreload_drd-amd64-linux.so)
==22308==    by 0x4E4F181: start_thread (pthread_create.c:312)
==22308==    by 0x515F47C: clone (clone.S:111)
==22308== Other segment end (thread 3)
==22308==    at 0x4C338E3: pthread_mutex_lock (in /usr/lib/valgrind/vgpreload_drd-amd64-linux.so)
==22308==    by 0x400BA28: _dl_add_to_namespace_list (dl-object.c:34)
==22308==    by 0x4006FC0: _dl_map_object_from_fd (dl-load.c:1599)
==22308==    by 0x4008DFF: _dl_map_object (dl-load.c:2605)
==22308==    by 0x4014A53: dl_open_worker (dl-open.c:235)
==22308==    by 0x400FFF3: _dl_catch_error (dl-error.c:187)
==22308==    by 0x40143BA: _dl_open (dl-open.c:661)
==22308==    by 0x519B0F1: do_dlopen (dl-libc.c:87)
==22308==    by 0x400FFF3: _dl_catch_error (dl-error.c:187)
==22308==    by 0x519B1B1: __libc_dlopen_mode (dl-libc.c:46)
==22308==    by 0x518244C: __nss_lookup_function (nsswitch.c:399)
==22308==    by 0x51825FD: __nss_lookup (nsswitch.c:229)