1  /* Test that pthread_cancel succeeds during thread exit.
       2     Copyright (C) 2021-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  /* This test tries to trigger an internal race condition in
      20     pthread_cancel, where the cancellation signal is sent after the
      21     thread has begun the cancellation process.  This can result in a
      22     spurious ESRCH error.  For the original bug 12889, the window is
      23     quite small, so the bug was not reproduced in every run.  */
      24  
      25  #include <stdbool.h>
      26  #include <stddef.h>
      27  #include <support/check.h>
      28  #include <support/xthread.h>
      29  #include <support/xunistd.h>
      30  #include <sys/select.h>
      31  #include <unistd.h>
      32  
      33  /* Set to true by timeout_thread_function when the test should
      34     terminate.  */
      35  static bool timeout;
      36  
      37  static void *
      38  timeout_thread_function (void *unused)
      39  {
      40    usleep (5 * 1000 * 1000);
      41    __atomic_store_n (&timeout, true, __ATOMIC_RELAXED);
      42    return NULL;
      43  }
      44  
      45  /* Used for blocking the select function below.  */
      46  static int pipe_fds[2];
      47  
      48  static void *
      49  canceled_thread_function (void *unused)
      50  {
      51    while (true)
      52      {
      53        fd_set rfs;
      54        fd_set wfs;
      55        fd_set efs;
      56        FD_ZERO (&rfs);
      57        FD_ZERO (&wfs);
      58        FD_ZERO (&efs);
      59        FD_SET (pipe_fds[0], &rfs);
      60  
      61        /* If the cancellation request is recognized early, the thread
      62           begins exiting while the cancellation signal arrives.  */
      63        select (FD_SETSIZE, &rfs, &wfs, &efs, NULL);
      64      }
      65    return NULL;
      66  }
      67  
      68  static int
      69  do_test (void)
      70  {
      71    xpipe (pipe_fds);
      72    pthread_t thr_timeout = xpthread_create (NULL, timeout_thread_function, NULL);
      73  
      74    while (!__atomic_load_n (&timeout, __ATOMIC_RELAXED))
      75      {
      76        pthread_t thr = xpthread_create (NULL, canceled_thread_function, NULL);
      77        xpthread_cancel (thr);
      78        TEST_VERIFY (xpthread_join (thr) == PTHREAD_CANCELED);
      79      }
      80  
      81    xpthread_join (thr_timeout);
      82    xclose (pipe_fds[0]);
      83    xclose (pipe_fds[1]);
      84    return 0;
      85  }
      86  
      87  #include <support/test-driver.c>