1 | /* Test case for async-signal-safe _Fork (with respect to malloc). |
2 | Copyright (C) 2021-2024 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 is similar to tst-mallocfork2.c, but specifically stress |
20 | the async-signal-safeness of _Fork on multithread environment. */ |
21 | |
22 | #include <array_length.h> |
23 | #include <errno.h> |
24 | #include <stdbool.h> |
25 | #include <stdio.h> |
26 | #include <stdlib.h> |
27 | #include <support/check.h> |
28 | #include <support/support.h> |
29 | #include <support/xsignal.h> |
30 | #include <support/xthread.h> |
31 | #include <support/xunistd.h> |
32 | #include <sys/wait.h> |
33 | |
34 | /* How many malloc objects to keep arond. */ |
35 | enum { malloc_objects = 1009 }; |
36 | |
37 | /* The maximum size of an object. */ |
38 | enum { malloc_maximum_size = 70000 }; |
39 | |
40 | /* How many iterations the test performs before exiting. */ |
41 | enum { iterations = 10000 }; |
42 | |
43 | /* Barrier for synchronization with the threads sending SIGUSR1 |
44 | signals, to make it more likely that the signals arrive during a |
45 | fork/free/malloc call. */ |
46 | static pthread_barrier_t barrier; |
47 | |
48 | /* Set to 1 if SIGUSR1 is received. Used to detect a signal during |
49 | fork/free/malloc. */ |
50 | static volatile sig_atomic_t sigusr1_received; |
51 | |
52 | /* Periodically set to 1, to indicate that the thread is making |
53 | progress. Checked by liveness_signal_handler. */ |
54 | static volatile sig_atomic_t progress_indicator = 1; |
55 | |
56 | /* Set to 1 if an error occurs in the signal handler. */ |
57 | static volatile sig_atomic_t error_indicator = 0; |
58 | |
59 | static void |
60 | sigusr1_handler (int signo) |
61 | { |
62 | sigusr1_received = 1; |
63 | |
64 | /* Perform a fork with a trivial subprocess. */ |
65 | pid_t pid = _Fork (); |
66 | if (pid == -1) |
67 | { |
68 | write_message (message: "error: fork\n" ); |
69 | error_indicator = 1; |
70 | return; |
71 | } |
72 | if (pid == 0) |
73 | _exit (0); |
74 | int status; |
75 | int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0)); |
76 | if (ret < 0) |
77 | { |
78 | write_message (message: "error: waitpid\n" ); |
79 | error_indicator = 1; |
80 | return; |
81 | } |
82 | if (status != 0) |
83 | { |
84 | write_message (message: "error: unexpected exit status from subprocess\n" ); |
85 | error_indicator = 1; |
86 | return; |
87 | } |
88 | } |
89 | |
90 | static void |
91 | liveness_signal_handler (int signo) |
92 | { |
93 | if (progress_indicator) |
94 | progress_indicator = 0; |
95 | else |
96 | write_message (message: "warning: thread seems to be stuck\n" ); |
97 | } |
98 | |
99 | struct signal_send_args |
100 | { |
101 | pthread_t target; |
102 | int signo; |
103 | bool sleep; |
104 | }; |
105 | #define SIGNAL_SEND_GET_ARG(arg, field) \ |
106 | (((struct signal_send_args *)(arg))->field) |
107 | |
108 | /* Send SIGNO to the parent thread. If SLEEP, wait a second between |
109 | signals, otherwise use barriers to delay sending signals. */ |
110 | static void * |
111 | signal_sender (void *args) |
112 | { |
113 | int signo = SIGNAL_SEND_GET_ARG (args, signo); |
114 | bool sleep = SIGNAL_SEND_GET_ARG (args, sleep); |
115 | |
116 | pthread_t target = SIGNAL_SEND_GET_ARG (args, target); |
117 | while (true) |
118 | { |
119 | if (!sleep) |
120 | xpthread_barrier_wait (barrier: &barrier); |
121 | xpthread_kill (thr: target, signo); |
122 | if (sleep) |
123 | usleep (useconds: 1 * 1000 * 1000); |
124 | else |
125 | xpthread_barrier_wait (barrier: &barrier); |
126 | } |
127 | return NULL; |
128 | } |
129 | |
130 | static pthread_t sigusr1_sender[5]; |
131 | static pthread_t sigusr2_sender; |
132 | |
133 | static int |
134 | do_test (void) |
135 | { |
136 | xsignal (SIGUSR1, handler: sigusr1_handler); |
137 | xsignal (SIGUSR2, handler: liveness_signal_handler); |
138 | |
139 | pthread_t self = pthread_self (); |
140 | |
141 | struct signal_send_args sigusr2_args = { self, SIGUSR2, true }; |
142 | sigusr2_sender = xpthread_create (NULL, thread_func: signal_sender, closure: &sigusr2_args); |
143 | |
144 | /* Send SIGUSR1 signals from several threads. Hopefully, one |
145 | signal will hit one of the critical functions. Use a barrier to |
146 | avoid sending signals while not running fork/free/malloc. */ |
147 | struct signal_send_args sigusr1_args = { self, SIGUSR1, false }; |
148 | xpthread_barrier_init (barrier: &barrier, NULL, |
149 | array_length (sigusr1_sender) + 1); |
150 | for (size_t i = 0; i < array_length (sigusr1_sender); ++i) |
151 | sigusr1_sender[i] = xpthread_create (NULL, thread_func: signal_sender, closure: &sigusr1_args); |
152 | |
153 | void *objects[malloc_objects] = {}; |
154 | unsigned int fork_signals = 0; |
155 | unsigned int free_signals = 0; |
156 | unsigned int malloc_signals = 0; |
157 | unsigned int seed = 1; |
158 | for (int i = 0; i < iterations; ++i) |
159 | { |
160 | progress_indicator = 1; |
161 | int slot = rand_r (seed: &seed) % malloc_objects; |
162 | size_t size = rand_r (seed: &seed) % malloc_maximum_size; |
163 | |
164 | /* Occasionally do a fork first, to catch deadlocks there as |
165 | well (see bug 24161). */ |
166 | bool do_fork = (rand_r (seed: &seed) % 7) == 0; |
167 | |
168 | xpthread_barrier_wait (barrier: &barrier); |
169 | if (do_fork) |
170 | { |
171 | sigusr1_received = 0; |
172 | pid_t pid = _Fork (); |
173 | TEST_VERIFY_EXIT (pid != -1); |
174 | if (sigusr1_received) |
175 | ++fork_signals; |
176 | if (pid == 0) |
177 | _exit (0); |
178 | int status; |
179 | int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0)); |
180 | if (ret < 0) |
181 | FAIL_EXIT1 ("waitpid: %m" ); |
182 | TEST_COMPARE (status, 0); |
183 | } |
184 | sigusr1_received = 0; |
185 | free (ptr: objects[slot]); |
186 | if (sigusr1_received) |
187 | ++free_signals; |
188 | sigusr1_received = 0; |
189 | objects[slot] = malloc (size: size); |
190 | if (sigusr1_received) |
191 | ++malloc_signals; |
192 | xpthread_barrier_wait (barrier: &barrier); |
193 | |
194 | if (objects[slot] == NULL || error_indicator != 0) |
195 | { |
196 | printf (format: "error: malloc: %m\n" ); |
197 | return 1; |
198 | } |
199 | } |
200 | |
201 | /* Clean up allocations. */ |
202 | for (int slot = 0; slot < malloc_objects; ++slot) |
203 | free (ptr: objects[slot]); |
204 | |
205 | printf (format: "info: signals received during fork: %u\n" , fork_signals); |
206 | printf (format: "info: signals received during free: %u\n" , free_signals); |
207 | printf (format: "info: signals received during malloc: %u\n" , malloc_signals); |
208 | |
209 | return 0; |
210 | } |
211 | |
212 | #define TIMEOUT 100 |
213 | #include <support/test-driver.c> |
214 | |