malloc/tst-mallocfork2.c

   1 /* Test case for async-signal-safe fork (with respect to malloc).
   2    Copyright (C) 2016-2018 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 <http://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
  38 /* How many malloc objects to keep arond.  */
  39 enum { malloc_objects = 1009 };
  40
  41 /* The maximum size of an object.  */
  42 enum { malloc_maximum_size = 70000 };
  43
  44 /* How many signals need to be delivered before the test exits.  */
  45 enum { signal_count = 1000 };
  46
  47 static int do_test (void);
  48 #define TIMEOUT 100
  49 #define TEST_FUNCTION do_test ()
  50 #include "../test-skeleton.c"
  51
  52 /* Process ID of the subprocess which sends SIGUSR1 signals.  */
  53 static pid_t sigusr1_sender_pid;
  54
  55 /* Set to 1 if SIGUSR1 is received.  Used to detect a signal during
  56    malloc/free.  */
  57 static volatile sig_atomic_t sigusr1_received;
  58
  59 /* Periodically set to 1, to indicate that the process is making
  60    progress.  Checked by liveness_signal_handler.  */
  61 static volatile sig_atomic_t progress_indicator = 1;
  62
  63 static void
  64 sigusr1_handler (int signo)
  65 {
  66   /* Let the main program make progress, by temporarily suspending
  67      signals from the subprocess.  */
  68   if (sigusr1_received)
  69     return;
  70   /* sigusr1_sender_pid might not be initialized in the parent when
  71      the first SIGUSR1 signal arrives.  */
  72   if (sigusr1_sender_pid > 0 && kill (sigusr1_sender_pid, SIGSTOP) != 0)
  73     {
  74       write_message ("error: kill (SIGSTOP)\n");
  75       abort ();
  76     }
  77   sigusr1_received = 1;
  78
  79   /* Perform a fork with a trivial subprocess.  */
  80   pid_t pid = fork ();
  81   if (pid == -1)
  82     {
  83       write_message ("error: fork\n");
  84       abort ();
  85     }
  86   if (pid == 0)
  87     _exit (0);
  88   int status;
  89   int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
  90   if (ret < 0)
  91     {
  92       write_message ("error: waitpid\n");
  93       abort ();
  94     }
  95   if (status != 0)
  96     {
  97       write_message ("error: unexpected exit status from subprocess\n");
  98       abort ();
  99     }
 100 }
 101
 102 static void
 103 liveness_signal_handler (int signo)
 104 {
 105   if (progress_indicator)
 106     progress_indicator = 0;
 107   else
 108     write_message ("warning: process seems to be stuck\n");
 109 }
 110
 111 static void
 112 __attribute__ ((noreturn))
 113 signal_sender (int signo, bool sleep)
 114 {
 115   pid_t target = getppid ();
 116   while (true)
 117     {
 118       if (kill (target, signo) != 0)
 119         {
 120           dprintf (STDOUT_FILENO, "error: kill: %m\n");
 121           abort ();
 122         }
 123       if (sleep)
 124         usleep (1 * 1000 * 1000);
 125       else
 126         /* Reduce the rate at which we send signals.  */
 127         sched_yield ();
 128     }
 129 }
 130
 131 static int
 132 do_test (void)
 133 {
 134   struct sigaction action =
 135     {
 136       .sa_handler = sigusr1_handler,
 137     };
 138   sigemptyset (&action.sa_mask);
 139
 140   if (sigaction (SIGUSR1, &action, NULL) != 0)
 141     {
 142       printf ("error: sigaction: %m");
 143       return 1;
 144     }
 145
 146   action.sa_handler = liveness_signal_handler;
 147   if (sigaction (SIGUSR2, &action, NULL) != 0)
 148     {
 149       printf ("error: sigaction: %m");
 150       return 1;
 151     }
 152
 153   pid_t sigusr2_sender_pid = fork ();
 154   if (sigusr2_sender_pid == 0)
 155     signal_sender (SIGUSR2, true);
 156   sigusr1_sender_pid = fork ();
 157   if (sigusr1_sender_pid == 0)
 158     signal_sender (SIGUSR1, false);
 159
 160   void *objects[malloc_objects] = {};
 161   unsigned signals = 0;
 162   unsigned seed = 1;
 163   time_t last_report = 0;
 164   while (signals < signal_count)
 165     {
 166       progress_indicator = 1;
 167       int slot = rand_r (&seed) % malloc_objects;
 168       size_t size = rand_r (&seed) % malloc_maximum_size;
 169       if (kill (sigusr1_sender_pid, SIGCONT) != 0)
 170         {
 171           printf ("error: kill (SIGCONT): %m\n");
 172           signal (SIGUSR1, SIG_IGN);
 173           kill (sigusr1_sender_pid, SIGKILL);
 174           kill (sigusr2_sender_pid, SIGKILL);
 175           return 1;
 176         }
 177       sigusr1_received = false;
 178       free (objects[slot]);
 179       objects[slot] = malloc (size);
 180       if (sigusr1_received)
 181         {
 182           ++signals;
 183           time_t current = time (0);
 184           if (current != last_report)
 185             {
 186               printf ("info: SIGUSR1 signal count: %u\n", signals);
 187               last_report = current;
 188             }
 189         }
 190       if (objects[slot] == NULL)
 191         {
 192           printf ("error: malloc: %m\n");
 193           signal (SIGUSR1, SIG_IGN);
 194           kill (sigusr1_sender_pid, SIGKILL);
 195           kill (sigusr2_sender_pid, SIGKILL);
 196           return 1;
 197         }
 198     }
 199
 200   /* Clean up allocations.  */
 201   for (int slot = 0; slot < malloc_objects; ++slot)
 202     free (objects[slot]);
 203
 204   /* Terminate the signal-sending subprocess.  The SIGUSR1 handler
 205      should no longer run because it uses sigusr1_sender_pid.  */
 206   signal (SIGUSR1, SIG_IGN);
 207   kill (sigusr1_sender_pid, SIGKILL);
 208   kill (sigusr2_sender_pid, SIGKILL);
 209
 210   return 0;
 211 }