nptl/tst-join7.c

   1 /* Verify that TLS access in separate thread in a dlopened library does not
   2    deadlock.
   3    Copyright (C) 2015-2019 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"