htl/tests/test-11.c

   1 /* Test rwlocks.
   2    Copyright (C) 2000-2023 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 #define _GNU_SOURCE
  20
  21 #include <pthread.h>
  22 #include <assert.h>
  23 #include <error.h>
  24 #include <errno.h>
  25
  26 #define THREADS 1
  27
  28 int a;
  29 int b;
  30
  31 /* Get a read lock and assert that a == b.  */
  32 void *
  33 test1 (void *arg)
  34 {
  35   error_t err;
  36   pthread_rwlock_t *lock = arg;
  37   int i;
  38
  39   for (i = 0; i < 200; i++)
  40     {
  41       err = pthread_rwlock_rdlock (lock);
  42       assert (err == 0);
  43
  44       assert (a == b);
  45
  46       sched_yield ();
  47
  48       assert (a == b);
  49
  50       err = pthread_rwlock_unlock (lock);
  51       assert (err == 0);
  52     }
  53
  54   return 0;
  55 }
  56
  57 int
  58 main (int argc, char **argv)
  59 {
  60   error_t err;
  61   pthread_rwlockattr_t attr;
  62   pthread_rwlock_t lock;
  63   int pshared;
  64
  65   int i;
  66   pthread_t tid[THREADS];
  67   void *ret;
  68
  69   err = pthread_rwlockattr_init (&attr);
  70   if (err)
  71     error (1, err, "pthread_rwlockattr_init");
  72
  73   err = pthread_rwlockattr_getpshared (&attr, &pshared);
  74   if (err)
  75     error (1, err, "pthread_rwlockattr_getpshared");
  76
  77   /* Assert the default state as mandated by POSIX.  */
  78   assert (pshared == PTHREAD_PROCESS_PRIVATE);
  79
  80   err = pthread_rwlockattr_setpshared (&attr, pshared);
  81   if (err)
  82     error (1, err, "pthread_rwlockattr_setpshared");
  83
  84   err = pthread_rwlock_init (&lock, &attr);
  85   if (err)
  86     error (1, err, "pthread_rwlock_init");
  87
  88   err = pthread_rwlockattr_destroy (&attr);
  89   if (err)
  90     error (1, err, "pthread_rwlockattr_destroy");
  91
  92   /* Now test the lock.  */
  93
  94   for (i = 0; i < THREADS; i++)
  95     {
  96       err = pthread_create (&tid[i], 0, test1, &lock);
  97       if (err)
  98         error (1, err, "pthread_create");
  99     }
 100
 101   for (i = 0; i < 10; i++)
 102     {
 103       sched_yield ();
 104
 105       /* Get a write lock.  */
 106       pthread_rwlock_wrlock (&lock);
 107       /* Increment a and b giving other threads a chance to run in
 108          between.  */
 109       sched_yield ();
 110       a++;
 111       sched_yield ();
 112       b++;
 113       sched_yield ();
 114       /* Unlock.  */
 115       pthread_rwlock_unlock (&lock);
 116     }
 117
 118   for (i = 0; i < THREADS; i++)
 119     {
 120       err = pthread_join (tid[i], &ret);
 121       if (err)
 122         error (1, err, "pthread_join");
 123     }
 124
 125   /* Read lock it.  */
 126   err = pthread_rwlock_tryrdlock (&lock);
 127   assert (err == 0);
 128
 129   /* Try to write lock it.  It should fail with EBUSY.  */
 130   err = pthread_rwlock_trywrlock (&lock);
 131   assert (err == EBUSY);
 132
 133   /* Drop the read lock.  */
 134   err = pthread_rwlock_unlock (&lock);
 135   assert (err == 0);
 136
 137   /* Get a write lock.  */
 138   err = pthread_rwlock_trywrlock (&lock);
 139   assert (err == 0);
 140
 141   /* Fail trying to acquire another write lock.  */
 142   err = pthread_rwlock_trywrlock (&lock);
 143   assert (err == EBUSY);
 144
 145   /* Try to get a read lock which should also fail.  */
 146   err = pthread_rwlock_tryrdlock (&lock);
 147   assert (err == EBUSY);
 148
 149   /* Unlock it.  */
 150   err = pthread_rwlock_unlock (&lock);
 151   assert (err == 0);
 152
 153
 154   err = pthread_rwlock_destroy (&lock);
 155   if (err)
 156     error (1, err, "pthread_rwlock_destroy");
 157
 158   return 0;
 159 }