malloc/tst-mallocfork2.c

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