File: tst-mallocfork2.c

package info (click to toggle)
glibc 2.28-8
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, experimental, sid
  • size: 271,788 kB
  • sloc: ansic: 1,008,637; asm: 259,607; makefile: 11,271; sh: 10,477; python: 6,910; cpp: 4,992; perl: 2,258; awk: 2,005; yacc: 290; pascal: 182; sed: 73
file content (211 lines) | stat: -rw-r--r-- 5,938 bytes parent folder | download | duplicates (4)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
/* Test case for async-signal-safe fork (with respect to malloc).
   Copyright (C) 2016-2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If
   not, see <http://www.gnu.org/licenses/>.  */

/* This test will fail if the process is multi-threaded because we
   only have an async-signal-safe fork in the single-threaded case
   (where we skip acquiring the malloc heap locks).

   This test only checks async-signal-safety with regards to malloc;
   other, more rarely-used glibc subsystems could have locks which
   still make fork unsafe, even in single-threaded processes.  */

#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

/* How many malloc objects to keep arond.  */
enum { malloc_objects = 1009 };

/* The maximum size of an object.  */
enum { malloc_maximum_size = 70000 };

/* How many signals need to be delivered before the test exits.  */
enum { signal_count = 1000 };

static int do_test (void);
#define TIMEOUT 100
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"

/* Process ID of the subprocess which sends SIGUSR1 signals.  */
static pid_t sigusr1_sender_pid;

/* Set to 1 if SIGUSR1 is received.  Used to detect a signal during
   malloc/free.  */
static volatile sig_atomic_t sigusr1_received;

/* Periodically set to 1, to indicate that the process is making
   progress.  Checked by liveness_signal_handler.  */
static volatile sig_atomic_t progress_indicator = 1;

static void
sigusr1_handler (int signo)
{
  /* Let the main program make progress, by temporarily suspending
     signals from the subprocess.  */
  if (sigusr1_received)
    return;
  /* sigusr1_sender_pid might not be initialized in the parent when
     the first SIGUSR1 signal arrives.  */
  if (sigusr1_sender_pid > 0 && kill (sigusr1_sender_pid, SIGSTOP) != 0)
    {
      write_message ("error: kill (SIGSTOP)\n");
      abort ();
    }
  sigusr1_received = 1;

  /* Perform a fork with a trivial subprocess.  */
  pid_t pid = fork ();
  if (pid == -1)
    {
      write_message ("error: fork\n");
      abort ();
    }
  if (pid == 0)
    _exit (0);
  int status;
  int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
  if (ret < 0)
    {
      write_message ("error: waitpid\n");
      abort ();
    }
  if (status != 0)
    {
      write_message ("error: unexpected exit status from subprocess\n");
      abort ();
    }
}

static void
liveness_signal_handler (int signo)
{
  if (progress_indicator)
    progress_indicator = 0;
  else
    write_message ("warning: process seems to be stuck\n");
}

static void
__attribute__ ((noreturn))
signal_sender (int signo, bool sleep)
{
  pid_t target = getppid ();
  while (true)
    {
      if (kill (target, signo) != 0)
        {
          dprintf (STDOUT_FILENO, "error: kill: %m\n");
          abort ();
        }
      if (sleep)
        usleep (1 * 1000 * 1000);
      else
        /* Reduce the rate at which we send signals.  */
        sched_yield ();
    }
}

static int
do_test (void)
{
  struct sigaction action =
    {
      .sa_handler = sigusr1_handler,
    };
  sigemptyset (&action.sa_mask);

  if (sigaction (SIGUSR1, &action, NULL) != 0)
    {
      printf ("error: sigaction: %m");
      return 1;
    }

  action.sa_handler = liveness_signal_handler;
  if (sigaction (SIGUSR2, &action, NULL) != 0)
    {
      printf ("error: sigaction: %m");
      return 1;
    }

  pid_t sigusr2_sender_pid = fork ();
  if (sigusr2_sender_pid == 0)
    signal_sender (SIGUSR2, true);
  sigusr1_sender_pid = fork ();
  if (sigusr1_sender_pid == 0)
    signal_sender (SIGUSR1, false);

  void *objects[malloc_objects] = {};
  unsigned signals = 0;
  unsigned seed = 1;
  time_t last_report = 0;
  while (signals < signal_count)
    {
      progress_indicator = 1;
      int slot = rand_r (&seed) % malloc_objects;
      size_t size = rand_r (&seed) % malloc_maximum_size;
      if (kill (sigusr1_sender_pid, SIGCONT) != 0)
        {
          printf ("error: kill (SIGCONT): %m\n");
          signal (SIGUSR1, SIG_IGN);
          kill (sigusr1_sender_pid, SIGKILL);
          kill (sigusr2_sender_pid, SIGKILL);
          return 1;
        }
      sigusr1_received = false;
      free (objects[slot]);
      objects[slot] = malloc (size);
      if (sigusr1_received)
        {
          ++signals;
          time_t current = time (0);
          if (current != last_report)
            {
              printf ("info: SIGUSR1 signal count: %u\n", signals);
              last_report = current;
            }
        }
      if (objects[slot] == NULL)
        {
          printf ("error: malloc: %m\n");
          signal (SIGUSR1, SIG_IGN);
          kill (sigusr1_sender_pid, SIGKILL);
          kill (sigusr2_sender_pid, SIGKILL);
          return 1;
        }
    }

  /* Clean up allocations.  */
  for (int slot = 0; slot < malloc_objects; ++slot)
    free (objects[slot]);

  /* Terminate the signal-sending subprocess.  The SIGUSR1 handler
     should no longer run because it uses sigusr1_sender_pid.  */
  signal (SIGUSR1, SIG_IGN);
  kill (sigusr1_sender_pid, SIGKILL);
  kill (sigusr2_sender_pid, SIGKILL);

  return 0;
}