1  /* Testing race while enabling lock elision.
       2     Copyright (C) 2018-2023 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  #include <stdio.h>
      19  #include <stdlib.h>
      20  #include <stdint.h>
      21  #include <pthread.h>
      22  #include <unistd.h>
      23  #include <getopt.h>
      24  #include <support/support.h>
      25  #include <support/xthread.h>
      26  
      27  static pthread_barrier_t barrier;
      28  static pthread_mutex_t mutex;
      29  static long long int iteration_count = 1000000;
      30  static unsigned int thread_count = 3;
      31  
      32  static void *
      33  thr_func (void *arg)
      34  {
      35    long long int i;
      36    for (i = 0; i < iteration_count; i++)
      37      {
      38        if ((uintptr_t) arg == 0)
      39  	{
      40  	  xpthread_mutex_destroy (&mutex);
      41  	  xpthread_mutex_init (&mutex, NULL);
      42  	}
      43  
      44        xpthread_barrier_wait (&barrier);
      45  
      46        /* Test if enabling lock elision works if it is enabled concurrently.
      47  	 There was a race in FORCE_ELISION macro which leads to either
      48  	 pthread_mutex_destroy returning EBUSY as the owner was recorded
      49  	 by pthread_mutex_lock - in "normal mutex" code path - but was not
      50  	 reset in pthread_mutex_unlock - in "elision" code path.
      51  	 Or it leads to the assertion in nptl/pthread_mutex_lock.c:
      52  	 assert (mutex->__data.__owner == 0);
      53  	 Please ensure that the test is run with lock elision:
      54  	 export GLIBC_TUNABLES=glibc.elision.enable=1  */
      55        xpthread_mutex_lock (&mutex);
      56        xpthread_mutex_unlock (&mutex);
      57  
      58        xpthread_barrier_wait (&barrier);
      59      }
      60    return NULL;
      61  }
      62  
      63  static int
      64  do_test (void)
      65  {
      66    unsigned int i;
      67    printf ("Starting %d threads to run %lld iterations.\n",
      68  	  thread_count, iteration_count);
      69  
      70    pthread_t *threads = xmalloc (thread_count * sizeof (pthread_t));
      71    xpthread_barrier_init (&barrier, NULL, thread_count);
      72    xpthread_mutex_init (&mutex, NULL);
      73  
      74    for (i = 0; i < thread_count; i++)
      75      threads[i] = xpthread_create (NULL, thr_func, (void *) (uintptr_t) i);
      76  
      77    for (i = 0; i < thread_count; i++)
      78      xpthread_join (threads[i]);
      79  
      80    xpthread_barrier_destroy (&barrier);
      81    free (threads);
      82  
      83    return EXIT_SUCCESS;
      84  }
      85  
      86  #define OPT_ITERATIONS	10000
      87  #define OPT_THREADS	10001
      88  #define CMDLINE_OPTIONS						\
      89    { "iterations", required_argument, NULL, OPT_ITERATIONS },	\
      90    { "threads", required_argument, NULL, OPT_THREADS },
      91  static void
      92  cmdline_process (int c)
      93  {
      94    long long int arg = strtoll (optarg, NULL, 0);
      95    switch (c)
      96      {
      97      case OPT_ITERATIONS:
      98        if (arg > 0)
      99  	iteration_count = arg;
     100        break;
     101      case OPT_THREADS:
     102        if (arg > 0 && arg < 100)
     103  	thread_count = arg;
     104        break;
     105      }
     106  }
     107  #define CMDLINE_PROCESS cmdline_process
     108  #define TIMEOUT 50
     109  #include <support/test-driver.c>