Bug#786397: glibc: deadlock in dlopen with TLS and threads

[Vincent Danjean <vdanjean@debian.org>]

Source: glibc
Version: 2.19-18
Severity: important

When using dlopen on a library with TLS and using threads in its constructor,
there can be a deadlock.

The bug is discuted here:
https://bugzilla.redhat.com/show_bug.cgi?id=1223055

Code to reproduce (taken from the above bug report):
main.c:

#include <stdio.h>
#include <dlfcn.h>
#include <assert.h>

int
main (void)
{
  void *h = dlopen ("./mod1.so", RTLD_NOW | RTLD_GLOBAL);
  assert (h != NULL);
  return 0;
}


mod1.cc:

#include <pthread.h>

class A
{
  private:
    int i;
  public:
    A () {i = 0;}
    ~A () {i = 42;}
    void hello (void) {}
};

thread_local A a;

static void *
thr (void *u)
{
  a.hello ();
  return NULL;
}

void
__attribute__((constructor))
init (void)
{
  pthread_t t;

  pthread_create (&t, NULL, thr, NULL);
  pthread_join (t, NULL);
}


Build mod1.cc with:

g++ -std=c++11 -shared -fPIC -g -o mod1.so mod1.cc -pthread


Note that, on Debian, I can observe the bug in the stable glibc version
(2.19-18) and also in the experimental one (2.21-0experimental0)

  Regards,
    Vincent

-- System Information:
Debian Release: 8.0
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'oldstable-updates'), (500, 'oldoldstable'), (500, 'unstable'), (500, 'testing'), (500, 'stable'), (500, 'oldstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, armel, mipsel

Kernel: Linux 3.19.0-trunk-amd64 (SMP w/8 CPU cores)
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