nptl/tst-rwlock16.c

   1 /* Copyright (C) 2015-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 /* This tests that with a reader-preferring rwlock, all readers are woken if
  19    one reader "steals" lock ownership from a blocked writer.  */
  20
  21 #include <errno.h>
  22 #include <pthread.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <semaphore.h>
  26 #include <unistd.h>
  27
  28 /* If we strictly prefer writers over readers, a program must not expect
  29    that, in the presence of concurrent writers, one reader will also acquire
  30    the lock when another reader has already done so.  Thus, use the
  31    default rwlock type that does not strictly prefer writers.  */
  32 static pthread_rwlock_t r = PTHREAD_RWLOCK_INITIALIZER;
  33
  34 static pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
  35 static pthread_cond_t cv = PTHREAD_COND_INITIALIZER;
  36
  37 /* Avoid using glibc-internal atomic operations.  */
  38 static sem_t stop;
  39 static int consumer_stop = 0;
  40
  41 static void *
  42 writer (void *arg)
  43 {
  44   int s;
  45
  46   do
  47     {
  48       if (pthread_rwlock_wrlock (&r) != 0)
  49         {
  50           puts ("wrlock failed");
  51           exit (EXIT_FAILURE);
  52         }
  53       if (pthread_rwlock_unlock (&r) != 0)
  54         {
  55           puts ("unlock failed");
  56           exit (EXIT_FAILURE);
  57         }
  58       sem_getvalue (&stop, &s);
  59     }
  60   while (s == 0);
  61   return NULL;
  62 }
  63
  64 static void *
  65 reader_producer (void *arg)
  66 {
  67   int s;
  68
  69   do
  70     {
  71       if (pthread_rwlock_rdlock (&r) != 0)
  72         {
  73           puts ("rdlock reader failed");
  74           exit (EXIT_FAILURE);
  75         }
  76
  77       sem_getvalue (&stop, &s);
  78
  79       pthread_mutex_lock (&m);
  80       if (s != 0)
  81         consumer_stop = 1;
  82       pthread_cond_signal (&cv);
  83       pthread_mutex_unlock (&m);
  84
  85       if (pthread_rwlock_unlock (&r) != 0)
  86         {
  87           puts ("unlock reader failed");
  88           exit (EXIT_FAILURE);
  89         }
  90     }
  91   while (s == 0);
  92   puts ("producer finished");
  93   return NULL;
  94 }
  95
  96 static void *
  97 reader_consumer (void *arg)
  98 {
  99   int s;
 100
 101   do
 102     {
 103       if (pthread_rwlock_rdlock (&r) != 0)
 104         {
 105           puts ("rdlock reader failed");
 106           exit (EXIT_FAILURE);
 107         }
 108
 109       pthread_mutex_lock (&m);
 110       s = consumer_stop;
 111       if (s == 0)
 112         pthread_cond_wait (&cv, &m);
 113       pthread_mutex_unlock (&m);
 114
 115       if (pthread_rwlock_unlock (&r) != 0)
 116         {
 117           puts ("unlock reader failed");
 118           exit (EXIT_FAILURE);
 119         }
 120     }
 121   while (s == 0);
 122     puts ("consumer finished");
 123   return NULL;
 124 }
 125
 126
 127 static int
 128 do_test (void)
 129 {
 130   pthread_t w1, w2, rp, rc;
 131
 132   if (pthread_create (&w1, NULL, writer, NULL) != 0)
 133     {
 134       puts ("create failed");
 135       return 1;
 136     }
 137   if (pthread_create (&w2, NULL, writer, NULL) != 0)
 138     {
 139       puts ("create failed");
 140       return 1;
 141     }
 142   if (pthread_create (&rc, NULL, reader_consumer, NULL) != 0)
 143     {
 144       puts ("create failed");
 145       return 1;
 146     }
 147   if (pthread_create (&rp, NULL, reader_producer, NULL) != 0)
 148     {
 149       puts ("create failed");
 150       return 1;
 151     }
 152
 153   sleep (2);
 154   sem_post (&stop);
 155
 156   if (pthread_join (w1, NULL) != 0)
 157     {
 158       puts ("w1 join failed");
 159       return 1;
 160     }
 161   if (pthread_join (w2, NULL) != 0)
 162     {
 163       puts ("w2 join failed");
 164       return 1;
 165     }
 166   if (pthread_join (rp, NULL) != 0)
 167     {
 168       puts ("reader_producer join failed");
 169       return 1;
 170     }
 171   if (pthread_join (rc, NULL) != 0)
 172     {
 173       puts ("reader_consumer join failed");
 174       return 1;
 175     }
 176
 177   return 0;
 178 }
 179
 180
 181 #define TIMEOUT 3
 182 #define TEST_FUNCTION do_test ()
 183 #include "../test-skeleton.c"