1 /* Bug 22111: Test that threads do not leak their per thread cache.
2 Copyright (C) 2015-2023 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
7 License as published by the Free Software Foundation; either
8 version 2.1 of the 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; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 /* The point of this test is to start and exit a large number of
20 threads, while at the same time looking to see if the used
21 memory grows with each round of threads run. If the memory
22 grows above some linear bound we declare the test failed and
23 that the malloc implementation is leaking memory with each
24 thread. This is a good indicator that the thread local cache
25 is leaking chunks. */
26
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <malloc.h>
30 #include <pthread.h>
31 #include <assert.h>
32 #include <libc-diag.h>
33
34 #include <support/check.h>
35 #include <support/support.h>
36 #include <support/xthread.h>
37
38 void *
39 worker (void *data)
40 {
41 void *ret;
42 /* Allocate an arbitrary amount of memory that is known to fit into
43 the thread local cache (tcache). If we have at least 64 bins
44 (default e.g. TCACHE_MAX_BINS) we should be able to allocate 32
45 bytes and force malloc to fill the tcache. We are assuming tcache
46 init happens at the first small alloc, but it might in the future
47 be deferred to some other point. Therefore to future proof this
48 test we include a full alloc/free/alloc cycle for the thread. We
49 need a compiler barrier to avoid the removal of the useless
50 alloc/free. We send some memory back to main to have the memory
51 freed after the thread dies, as just another check that the chunks
52 that were previously in the tcache are still OK to free after
53 thread death. */
54 ret = xmalloc (32);
55 __asm__ volatile ("" ::: "memory");
56 free (ret);
57 return (void *) xmalloc (32);
58 }
59
60 static int
61 do_test (void)
62 {
63 pthread_t *thread;
64 struct mallinfo info_before, info_after;
65 void *retval;
66
67 /* This is an arbitrary choice. We choose a total of THREADS
68 threads created and joined. This gives us enough iterations to
69 show a leak. */
70 int threads = 100000;
71
72 /* Avoid there being 0 malloc'd data at this point by allocating the
73 pthread_t required to run the test. */
74 thread = (pthread_t *) xcalloc (1, sizeof (pthread_t));
75
76 /* The test below covers the deprecated mallinfo function. */
77 DIAG_PUSH_NEEDS_COMMENT;
78 DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wdeprecated-declarations");
79
80 info_before = mallinfo ();
81
82 assert (info_before.uordblks != 0);
83
84 printf ("INFO: %d (bytes) are in use before starting threads.\n",
85 info_before.uordblks);
86
87 for (int loop = 0; loop < threads; loop++)
88 {
89 *thread = xpthread_create (NULL, worker, NULL);
90 retval = xpthread_join (*thread);
91 free (retval);
92 }
93
94 info_after = mallinfo ();
95 printf ("INFO: %d (bytes) are in use after all threads joined.\n",
96 info_after.uordblks);
97
98 /* We need to compare the memory in use before and the memory in use
99 after starting and joining THREADS threads. We almost always grow
100 memory slightly, but not much. Consider that if even 1-byte leaked
101 per thread we'd have THREADS bytes of additional memory, and in
102 general the in-use at the start of main is quite low. We will
103 always leak a full malloc chunk, and never just 1-byte, therefore
104 anything above "+ threads" from the start (constant offset) is a
105 leak. Obviously this assumes no thread-related malloc'd internal
106 libc data structures persist beyond the thread death, and any that
107 did would limit the number of times you could call pthread_create,
108 which is a QoI we'd want to detect and fix. */
109 if (info_after.uordblks > (info_before.uordblks + threads))
110 FAIL_EXIT1 ("Memory usage after threads is too high.\n");
111
112 DIAG_POP_NEEDS_COMMENT;
113
114 /* Did not detect excessive memory usage. */
115 free (thread);
116 exit (0);
117 }
118
119 #define TIMEOUT 50
120 #include <support/test-driver.c>