1  /* Verify that TLS access in separate thread in a dlopened library does not
       2     deadlock.
       3     Copyright (C) 2015-2023 Free Software Foundation, Inc.
       4     This file is part of the GNU C Library.
       5  
       6     The GNU C Library is free software; you can redistribute it and/or
       7     modify it under the terms of the GNU Lesser General Public
       8     License as published by the Free Software Foundation; either
       9     version 2.1 of the License, or (at your option) any later version.
      10  
      11     The GNU C Library is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14     Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public
      17     License along with the GNU C Library; if not, see
      18     <https://www.gnu.org/licenses/>.  */
      19  
      20  #include <dlfcn.h>
      21  
      22  /* When one dynamically loads a module, which spawns a thread to perform some
      23     activities, it could be possible that TLS storage is accessed for the first
      24     time in that thread.  This results in an allocation request within the
      25     thread, which could result in an attempt to take the rtld load_lock.  This
      26     is a problem because it would then deadlock with the dlopen (which owns the
      27     lock), if the main thread is waiting for the spawned thread to exit.  We can
      28     at least ensure that this problem does not occur due to accesses within
      29     libc.so, by marking TLS variables within libc.so as IE.  The problem of an
      30     arbitrary variable being accessed and constructed within such a thread still
      31     exists but this test case does not verify that.  */
      32  
      33  int
      34  do_test (void)
      35  {
      36    void *f = dlopen ("tst-join7mod.so", RTLD_NOW | RTLD_GLOBAL);
      37    if (f)
      38      dlclose (f);
      39    else
      40      return 1;
      41  
      42    return 0;
      43  }
      44  
      45  #define TEST_FUNCTION do_test ()
      46  #include "../test-skeleton.c"