malloc/tst-mallocfork2.c

   1 /* Test case for async-signal-safe fork (with respect to malloc).
   2    Copyright (C) 2016-2019 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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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; see the file COPYING.LIB.  If
  17    not, see <https://www.gnu.org/licenses/>.  */
  18
  19 /* This test will fail if the process is multi-threaded because we
  20    only have an async-signal-safe fork in the single-threaded case
  21    (where we skip acquiring the malloc heap locks).
  22
  23    This test only checks async-signal-safety with regards to malloc;
  24    other, more rarely-used glibc subsystems could have locks which
  25    still make fork unsafe, even in single-threaded processes.  */
  26
  27 #include <errno.h>
  28 #include <sched.h>
  29 #include <signal.h>
  30 #include <stdbool.h>
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include <sys/wait.h>
  35 #include <time.h>
  36 #include <unistd.h>
  37 #include <array_length.h>
  38 #include <support/check.h>
  39 #include <support/support.h>
  40 #include <support/xthread.h>
  41 #include <support/xunistd.h>
  42
  43 /* How many malloc objects to keep arond.  */
  44 enum { malloc_objects = 1009 };
  45
  46 /* The maximum size of an object.  */
  47 enum { malloc_maximum_size = 70000 };
  48
  49 /* How many iterations the test performs before exiting.  */
  50 enum { iterations = 10000 };
  51
  52 /* Barrier for synchronization with the processes sending SIGUSR1
  53    signals, to make it more likely that the signals arrive during a
  54    fork/free/malloc call.  */
  55 static struct { pthread_barrier_t barrier; } *shared;
  56
  57 /* Set to 1 if SIGUSR1 is received.  Used to detect a signal during
  58    fork/free/malloc.  */
  59 static volatile sig_atomic_t sigusr1_received;
  60
  61 /* Periodically set to 1, to indicate that the process is making
  62    progress.  Checked by liveness_signal_handler.  */
  63 static volatile sig_atomic_t progress_indicator = 1;
  64
  65 static void
  66 sigusr1_handler (int signo)
  67 {
  68   sigusr1_received = 1;
  69
  70   /* Perform a fork with a trivial subprocess.  */
  71   pid_t pid = fork ();
  72   if (pid == -1)
  73     {
  74       write_message ("error: fork\n");
  75       abort ();
  76     }
  77   if (pid == 0)
  78     _exit (0);
  79   int status;
  80   int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
  81   if (ret < 0)
  82     {
  83       write_message ("error: waitpid\n");
  84       abort ();
  85     }
  86   if (status != 0)
  87     {
  88       write_message ("error: unexpected exit status from subprocess\n");
  89       abort ();
  90     }
  91 }
  92
  93 static void
  94 liveness_signal_handler (int signo)
  95 {
  96   if (progress_indicator)
  97     progress_indicator = 0;
  98   else
  99     write_message ("warning: process seems to be stuck\n");
 100 }
 101
 102 /* Send SIGNO to the parent process.  If SLEEP, wait a second between
 103    signals, otherwise use barriers to delay sending signals.  */
 104 static void
 105 __attribute__ ((noreturn))
 106 signal_sender (int signo, bool sleep)
 107 {
 108   pid_t target = getppid ();
 109   while (true)
 110     {
 111       if (!sleep)
 112         xpthread_barrier_wait (&shared->barrier);
 113       if (kill (target, signo) != 0)
 114         {
 115           dprintf (STDOUT_FILENO, "error: kill: %m\n");
 116           abort ();
 117         }
 118       if (sleep)
 119         usleep (1 * 1000 * 1000);
 120       else
 121         xpthread_barrier_wait (&shared->barrier);
 122     }
 123 }
 124
 125 static int
 126 do_test (void)
 127 {
 128   /* shared->barrier is intialized along with sigusr1_sender_pids
 129      below.  */
 130   shared = support_shared_allocate (sizeof (*shared));
 131
 132   struct sigaction action =
 133     {
 134       .sa_handler = sigusr1_handler,
 135     };
 136   sigemptyset (&action.sa_mask);
 137
 138   if (sigaction (SIGUSR1, &action, NULL) != 0)
 139     {
 140       printf ("error: sigaction: %m");
 141       return 1;
 142     }
 143
 144   action.sa_handler = liveness_signal_handler;
 145   if (sigaction (SIGUSR2, &action, NULL) != 0)
 146     {
 147       printf ("error: sigaction: %m");
 148       return 1;
 149     }
 150
 151   pid_t sigusr2_sender_pid = xfork ();
 152   if (sigusr2_sender_pid == 0)
 153     signal_sender (SIGUSR2, true);
 154
 155   /* Send SIGUSR1 signals from several processes.  Hopefully, one
 156      signal will hit one of the ciritical functions.  Use a barrier to
 157      avoid sending signals while not running fork/free/malloc.  */
 158   pid_t sigusr1_sender_pids[5];
 159   {
 160     pthread_barrierattr_t attr;
 161     xpthread_barrierattr_init (&attr);
 162     xpthread_barrierattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
 163     xpthread_barrier_init (&shared->barrier, &attr,
 164                            array_length (sigusr1_sender_pids) + 1);
 165     xpthread_barrierattr_destroy (&attr);
 166   }
 167   for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i)
 168     {
 169       sigusr1_sender_pids[i] = fork ();
 170       if (sigusr1_sender_pids[i] == 0)
 171         signal_sender (SIGUSR1, false);
 172     }
 173
 174   void *objects[malloc_objects] = {};
 175   unsigned int fork_signals = 0;
 176   unsigned int free_signals = 0;
 177   unsigned int malloc_signals = 0;
 178   unsigned seed = 1;
 179   for (int i = 0; i < iterations; ++i)
 180     {
 181       progress_indicator = 1;
 182       int slot = rand_r (&seed) % malloc_objects;
 183       size_t size = rand_r (&seed) % malloc_maximum_size;
 184
 185       /* Occasionally do a fork first, to catch deadlocks there as
 186          well (see bug 24161).  */
 187       bool do_fork = (rand_r (&seed) % 7) == 0;
 188
 189       xpthread_barrier_wait (&shared->barrier);
 190       if (do_fork)
 191         {
 192           sigusr1_received = 0;
 193           pid_t pid = xfork ();
 194           if (sigusr1_received)
 195             ++fork_signals;
 196           if (pid == 0)
 197             _exit (0);
 198           int status;
 199           int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
 200           if (ret < 0)
 201             FAIL_EXIT1 ("waitpid: %m");
 202           TEST_COMPARE (status, 0);
 203         }
 204       sigusr1_received = 0;
 205       free (objects[slot]);
 206       if (sigusr1_received)
 207         ++free_signals;
 208       sigusr1_received = 0;
 209       objects[slot] = malloc (size);
 210       if (sigusr1_received)
 211         ++malloc_signals;
 212       xpthread_barrier_wait (&shared->barrier);
 213
 214       if (objects[slot] == NULL)
 215         {
 216           printf ("error: malloc: %m\n");
 217           for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i)
 218             kill (sigusr1_sender_pids[i], SIGKILL);
 219           kill (sigusr2_sender_pid, SIGKILL);
 220           return 1;
 221         }
 222     }
 223
 224   /* Clean up allocations.  */
 225   for (int slot = 0; slot < malloc_objects; ++slot)
 226     free (objects[slot]);
 227
 228   for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i)
 229     kill (sigusr1_sender_pids[i], SIGKILL);
 230   kill (sigusr2_sender_pid, SIGKILL);
 231
 232   printf ("info: signals received during fork: %u\n", fork_signals);
 233   printf ("info: signals received during free: %u\n", free_signals);
 234   printf ("info: signals received during malloc: %u\n", malloc_signals);
 235
 236   /* Do not destroy the barrier because of the SIGKILL above, which
 237      may have left the barrier in an inconsistent state.  */
 238   support_shared_free (shared);
 239
 240   return 0;
 241 }
 242
 243 #define TIMEOUT 100
 244 #include <support/test-driver.c>