I just found that python consider linux implementation of getaddrinfo thread safe :

./python2.6-2.6.8/Modules/socketmodule.c:180

/* On systems on which getaddrinfo() is believed to not be thread-safe,                                                                                                                                                             
   (this includes the getaddrinfo emulation) protect access with a lock. */
#if defined(WITH_THREAD) && (defined(__APPLE__) || \
    (defined(__FreeBSD__) && __FreeBSD_version+0 < 503000) || \
    defined(__OpenBSD__) || defined(__NetBSD__) || \
    defined(__VMS) || !defined(HAVE_GETADDRINFO))
#define USE_GETADDRINFO_LOCK
#endif

Badly, it's wrong on my version of linux, and maybe others : https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=722075

So for me, looping in three threads on getaddrinfo leads me to a rapid deadlock, while reading on a NETLINK socket, after another thread wrote a DNS query on it and trying to get a response on it.

It may only be reproductible when your getaddrinfo use a NETLINK to get informations about your interfaces before doing the DNS query.

Can you attach some python code that reproduces this for you?  According to both of the references below it doesn't sound like this is supposed to be a problem.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/freeaddrinfo.html claims "The freeaddrinfo() and getaddrinfo() functions shall be thread-safe."

Linux man pages claim "getaddrinfo() is reentrant".

> It may only be reproductible when your getaddrinfo use a NETLINK to get informations about your interfaces before doing the DNS query.

What is your operation system? Name and version. What is your version of the C library? What is your Python version? Can you provide an example to reproduce the issue?

test_getaddrinfo.c: C program to run getaddrinfo() concurrently in different threads, it comes from the Debian issue.

I ran this program with 10 threads, I stopped it after between 3000 and 5000 tries (depending on the thread). I'm running Fedora 20: Linux kernel 3.13.9-200.fc20.x86_64 and glibc 2.18.

Can you provide the C and Python backtrace of all threads of your program?

@Julien.Palard: Ping? Without more information, I would suggest to close the issue.

The upstream Debian issue contains a fix for the bug in eglibc. Python should not attempt to work around this. Distros need to fix their libc if they shipped a broken one.