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1 | /* Bug 20116: Test rapid creation of detached threads. |
2 | Copyright (C) 2017 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; see the file COPYING.LIB. If | |
17 | not, see <http://www.gnu.org/licenses/>. */ | |
18 | ||
19 | /* The goal of the test is to trigger a failure if the parent touches | |
20 | any part of the thread descriptor after the detached thread has | |
21 | exited. We test this by creating many detached threads with large | |
22 | stacks. The stacks quickly fill the the stack cache and subsequent | |
23 | threads will start to cause the thread stacks to be immediately | |
24 | unmapped to satisfy the stack cache max. With the stacks being | |
25 | unmapped the parent's read of any part of the thread descriptor will | |
26 | trigger a segfault. That segfault is what we are trying to cause, | |
27 | since any segfault is a defect in the implementation. */ | |
28 | ||
29 | #include <pthread.h> | |
30 | #include <stdio.h> | |
31 | #include <errno.h> | |
32 | #include <unistd.h> | |
33 | #include <stdbool.h> | |
34 | #include <sys/resource.h> | |
35 | #include <support/xthread.h> | |
36 | ||
37 | /* Number of threads to create. */ | |
38 | enum { threads_to_create = 100000 }; | |
39 | ||
40 | /* Number of threads which should spawn other threads. */ | |
41 | enum { creator_threads = 2 }; | |
42 | ||
43 | /* Counter of threads created so far. This is incremented by all the | |
44 | running creator threads. */ | |
45 | static unsigned threads_created; | |
46 | ||
47 | /* Thread callback which does nothing, so that the thread exits | |
48 | immediatedly. */ | |
49 | static void * | |
50 | do_nothing (void *arg) | |
51 | { | |
52 | return NULL; | |
53 | } | |
54 | ||
55 | /* Attribute indicating that the thread should be created in a detached | |
56 | fashion. */ | |
57 | static pthread_attr_t detached; | |
58 | ||
59 | /* Barrier to synchronize initialization. */ | |
60 | static pthread_barrier_t barrier; | |
61 | ||
62 | static void * | |
63 | creator_thread (void *arg) | |
64 | { | |
65 | int ret; | |
66 | xpthread_barrier_wait (&barrier); | |
67 | ||
68 | while (true) | |
69 | { | |
70 | pthread_t thr; | |
71 | /* Thread creation will fail if the kernel does not free old | |
72 | threads quickly enough, so we do not report errors. */ | |
73 | ret = pthread_create (&thr, &detached, do_nothing, NULL); | |
74 | if (ret == 0 && __atomic_add_fetch (&threads_created, 1, __ATOMIC_SEQ_CST) | |
75 | >= threads_to_create) | |
76 | break; | |
77 | } | |
78 | ||
79 | return NULL; | |
80 | } | |
81 | ||
82 | static int | |
83 | do_test (void) | |
84 | { | |
85 | /* Limit the size of the process, so that memory allocation will | |
86 | fail without impacting the entire system. */ | |
87 | { | |
88 | struct rlimit limit; | |
89 | if (getrlimit (RLIMIT_AS, &limit) != 0) | |
90 | { | |
91 | printf ("FAIL: getrlimit (RLIMIT_AS) failed: %m\n"); | |
92 | return 1; | |
93 | } | |
94 | /* This limit, 800MB, is just a heuristic. Any value can be | |
95 | picked. */ | |
96 | long target = 800 * 1024 * 1024; | |
97 | if (limit.rlim_cur == RLIM_INFINITY || limit.rlim_cur > target) | |
98 | { | |
99 | limit.rlim_cur = target; | |
100 | if (setrlimit (RLIMIT_AS, &limit) != 0) | |
101 | { | |
102 | printf ("FAIL: setrlimit (RLIMIT_AS) failed: %m\n"); | |
103 | return 1; | |
104 | } | |
105 | } | |
106 | } | |
107 | ||
108 | xpthread_attr_init (&detached); | |
109 | ||
110 | xpthread_attr_setdetachstate (&detached, PTHREAD_CREATE_DETACHED); | |
111 | ||
112 | /* A large thread stack seems beneficial for reproducing a race | |
113 | condition in detached thread creation. The goal is to reach the | |
114 | limit of the runtime thread stack cache such that the detached | |
115 | thread's stack is unmapped after exit and causes a segfault when | |
116 | the parent reads the thread descriptor data stored on the the | |
117 | unmapped stack. */ | |
118 | xpthread_attr_setstacksize (&detached, 16 * 1024 * 1024); | |
119 | ||
120 | xpthread_barrier_init (&barrier, NULL, creator_threads); | |
121 | ||
122 | pthread_t threads[creator_threads]; | |
123 | ||
124 | for (int i = 0; i < creator_threads; ++i) | |
125 | threads[i] = xpthread_create (NULL, creator_thread, NULL); | |
126 | ||
127 | for (int i = 0; i < creator_threads; ++i) | |
128 | xpthread_join (threads[i]); | |
129 | ||
130 | xpthread_attr_destroy (&detached); | |
131 | ||
132 | xpthread_barrier_destroy (&barrier); | |
133 | ||
134 | return 0; | |
135 | } | |
136 | ||
3cefdd73 | 137 | #define TIMEOUT 100 |
f8bf15fe | 138 | #include <support/test-driver.c> |