nptl/tst-robust-fork.c

   1 /* Test the interaction of fork and robust mutexes.
   2    Copyright (C) 2017-2021 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 #include <errno.h>
  20 #include <stdbool.h>
  21 #include <stdio.h>
  22 #include <support/check.h>
  23 #include <support/test-driver.h>
  24 #include <support/xthread.h>
  25 #include <support/xunistd.h>
  26 #include <sys/mman.h>
  27
  28 /* Data shared between processes. */
  29 struct shared
  30 {
  31   pthread_mutex_t parent_mutex;
  32   pthread_mutex_t child_mutex;
  33 };
  34
  35 /* These flags control which mutex settings are enabled in the parent
  36    and child (separately).  */
  37 enum mutex_bits
  38   {
  39     mutex_pshared = 1,
  40     mutex_robust = 2,
  41     mutex_pi = 4,
  42     mutex_check = 8,
  43
  44     /* All bits combined.  */
  45     mutex_all_bits = 15,
  46   };
  47
  48 static void
  49 mutex_init (pthread_mutex_t *mutex, int bits)
  50 {
  51   pthread_mutexattr_t attr;
  52   xpthread_mutexattr_init (&attr);
  53   if (bits & mutex_pshared)
  54     xpthread_mutexattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
  55   if (bits & mutex_robust)
  56     xpthread_mutexattr_setrobust (&attr, PTHREAD_MUTEX_ROBUST);
  57   if (bits & mutex_pi)
  58     xpthread_mutexattr_setprotocol (&attr, PTHREAD_PRIO_INHERIT);
  59   if (bits & mutex_check)
  60     xpthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK);
  61   xpthread_mutex_init (mutex, &attr);
  62   xpthread_mutexattr_destroy (&attr);
  63 }
  64
  65 static void
  66 one_test (int parent_bits, int child_bits, int nonshared_bits,
  67           bool lock_nonshared, bool lock_child)
  68 {
  69
  70   struct shared *shared = xmmap (NULL, sizeof (*shared),
  71                                  PROT_READ | PROT_WRITE,
  72                                  MAP_ANONYMOUS | MAP_SHARED, -1);
  73   mutex_init (&shared->parent_mutex, parent_bits);
  74   mutex_init (&shared->child_mutex, child_bits);
  75
  76   /* Acquire the parent mutex in the parent.  */
  77   xpthread_mutex_lock (&shared->parent_mutex);
  78
  79   pthread_mutex_t nonshared_mutex;
  80   mutex_init (&nonshared_mutex, nonshared_bits);
  81   if (lock_nonshared)
  82     xpthread_mutex_lock (&nonshared_mutex);
  83
  84   pid_t pid = xfork ();
  85   if (pid == 0)
  86     {
  87       /* Child process.  */
  88       if (lock_child)
  89         xpthread_mutex_lock (&shared->child_mutex);
  90       else
  91         xmunmap (shared, sizeof (*shared));
  92       if (lock_nonshared)
  93         /* Reinitialize the non-shared mutex if it was locked in the
  94            parent.  */
  95         mutex_init (&nonshared_mutex, nonshared_bits);
  96       xpthread_mutex_lock (&nonshared_mutex);
  97       /* For robust mutexes, the _exit call will perform the unlock
  98          instead.  */
  99       if (lock_child && !(child_bits & mutex_robust))
 100         xpthread_mutex_unlock (&shared->child_mutex);
 101       _exit (0);
 102     }
 103   /* Parent process. */
 104   {
 105     int status;
 106     xwaitpid (pid, &status, 0);
 107     TEST_VERIFY (status == 0);
 108   }
 109
 110   if (parent_bits & mutex_check)
 111     /* Test for expected self-deadlock.  This is only possible to
 112        detect if the mutex is error-checking.  */
 113     TEST_VERIFY_EXIT (pthread_mutex_lock (&shared->parent_mutex) == EDEADLK);
 114
 115   pid = xfork ();
 116   if (pid == 0)
 117     {
 118       /* Child process.  We can perform some checks only if we are
 119          dealing with process-shared mutexes.  */
 120       if (parent_bits & mutex_pshared)
 121         /* It must not be possible to acquire the parent mutex.
 122
 123            NB: This check touches a mutex which has been acquired in
 124            the parent at fork time, so it might be deemed undefined
 125            behavior, pending the resolution of Austin Groups issue
 126            1112.  */
 127         TEST_VERIFY_EXIT (pthread_mutex_trylock (&shared->parent_mutex)
 128                           == EBUSY);
 129       if (lock_child && (child_bits & mutex_robust))
 130         {
 131           if (!(child_bits & mutex_pshared))
 132             /* No further tests possible.  */
 133             _exit (0);
 134           TEST_VERIFY_EXIT (pthread_mutex_lock (&shared->child_mutex)
 135                             == EOWNERDEAD);
 136           xpthread_mutex_consistent (&shared->child_mutex);
 137         }
 138       else
 139         /* We did not acquire the lock in the first child process, or
 140            we unlocked the mutex again because the mutex is not a
 141            robust mutex.  */
 142         xpthread_mutex_lock (&shared->child_mutex);
 143       xpthread_mutex_unlock (&shared->child_mutex);
 144       _exit (0);
 145     }
 146   /* Parent process. */
 147   {
 148     int status;
 149     xwaitpid (pid, &status, 0);
 150     TEST_VERIFY (status == 0);
 151   }
 152
 153   if (lock_nonshared)
 154     xpthread_mutex_unlock (&nonshared_mutex);
 155   xpthread_mutex_unlock (&shared->parent_mutex);
 156   xpthread_mutex_destroy (&shared->parent_mutex);
 157   xpthread_mutex_destroy (&shared->child_mutex);
 158   xpthread_mutex_destroy (&nonshared_mutex);
 159   xmunmap (shared, sizeof (*shared));
 160 }
 161
 162 static int
 163 do_test (void)
 164 {
 165   for (int parent_bits = 0; parent_bits <= mutex_all_bits; ++parent_bits)
 166     for (int child_bits = 0; child_bits <= mutex_all_bits; ++child_bits)
 167       for (int nonshared_bits = 0; nonshared_bits <= mutex_all_bits;
 168            ++nonshared_bits)
 169         for (int lock_nonshared = 0; lock_nonshared < 2; ++lock_nonshared)
 170           for (int lock_child = 0; lock_child < 2; ++lock_child)
 171             {
 172               if (test_verbose)
 173                 printf ("info: parent_bits=0x%x child_bits=0x%x"
 174                         " nonshared_bits=0x%x%s%s\n",
 175                         parent_bits, child_bits, nonshared_bits,
 176                         lock_nonshared ? " lock_nonshared" : "",
 177                         lock_child ? " lock_child" : "");
 178               one_test (parent_bits, child_bits, nonshared_bits,
 179                         lock_nonshared, lock_child);
 180             }
 181   return 0;
 182 }
 183
 184 #define TIMEOUT 100
 185 #include <support/test-driver.c>