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1 | .\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk |
2 | .\" <mtk.manpages@gmail.com> | |
3 | .\" | |
4 | .\" Permission is granted to make and distribute verbatim copies of this | |
5 | .\" manual provided the copyright notice and this permission notice are | |
6 | .\" preserved on all copies. | |
7 | .\" | |
8 | .\" Permission is granted to copy and distribute modified versions of this | |
9 | .\" manual under the conditions for verbatim copying, provided that the | |
10 | .\" entire resulting derived work is distributed under the terms of a | |
11 | .\" permission notice identical to this one. | |
12 | .\" | |
13 | .\" Since the Linux kernel and libraries are constantly changing, this | |
14 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
15 | .\" responsibility for errors or omissions, or for damages resulting from | |
16 | .\" the use of the information contained herein. The author(s) may not | |
17 | .\" have taken the same level of care in the production of this manual, | |
18 | .\" which is licensed free of charge, as they might when working | |
19 | .\" professionally. | |
20 | .\" | |
21 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
23 | .\" | |
48718eb3 | 24 | .TH PTHREAD_JOIN 3 2008-11-27 "Linux" "Linux Programmer's Manual" |
ebdd7ee1 MK |
25 | .SH NAME |
26 | pthread_join \- join with a terminated thread | |
27 | .SH SYNOPSIS | |
28 | .nf | |
29 | .B #include <pthread.h> | |
30 | ||
31 | .BI "int pthread_join(pthread_t " thread ", void **" retval ); | |
32 | .fi | |
33 | .sp | |
34 | Compile and link with \fI\-pthread\fP. | |
35 | .SH DESCRIPTION | |
36 | The | |
37 | .BR pthread_join () | |
38 | function waits for the thread specified by | |
39 | .IR thread | |
40 | to terminate. | |
41 | If that thread has already terminated, then | |
42 | .BR pthread_join () | |
43 | returns immediately. | |
44 | The thread specified by | |
45 | .I thread | |
46 | must be joinable. | |
47 | ||
48 | If | |
49 | .I retval | |
50 | is not NULL, then | |
51 | .BR pthread_join () | |
52 | copies the exit status of the target thread | |
53 | (i.e., the value that the target thread supplied to | |
54 | .BR pthread_exit (3)) | |
55 | into the location pointed to by | |
56 | .IR *retval . | |
57 | If the target thread was canceled, then | |
58 | .B PTHREAD_CANCELED | |
59 | is placed in | |
60 | .IR *retval . | |
61 | ||
62 | If multiple threads simultaneously try to join with the same thread, | |
63 | the results are undefined. | |
64 | If the thread calling | |
65 | .BR pthread_join () | |
66 | is canceled, then the target thread will remain joinable | |
67 | (i.e., it will not be detached). | |
68 | .SH RETURN VALUE | |
69 | On success, | |
70 | .BR pthread_join () | |
71 | returns 0; | |
72 | on error, it returns an error number. | |
73 | .SH ERRORS | |
74 | .TP | |
75 | .B EDEADLK | |
76 | A deadlock was detected | |
77 | .\" The following verified by testing on glibc 2.8/NPTL: | |
78 | (e.g., two threads tried to join with each other); | |
79 | or | |
80 | .\" The following verified by testing on glibc 2.8/NPTL: | |
81 | .I thread | |
82 | specifies the calling thread. | |
83 | .TP | |
84 | .B EINVAL | |
85 | .I thread | |
86 | is not a joinable thread. | |
bbb08de3 MK |
87 | .TP |
88 | .B EINVAL | |
89 | Another thread is already waiting to join with this thread. | |
90 | .\" POSIX.1-2001 does not specify this error case. | |
ebdd7ee1 MK |
91 | .TP |
92 | .B ESRCH | |
48718eb3 MK |
93 | No thread with the ID |
94 | .I thread | |
95 | could be found. | |
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96 | .SH CONFORMING TO |
97 | POSIX.1-2001. | |
98 | .SH NOTES | |
99 | After a successful call to | |
100 | .BR pthread_create (), | |
101 | the caller is guaranteed that the target thread has terminated. | |
102 | ||
103 | Joining with a thread that has previously been joined results in | |
240c2fa0 | 104 | undefined behavior. |
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105 | |
106 | Failure to join with a thread that is joinable | |
107 | (i.e., one that is not detached), | |
108 | produces a "zombie thread". | |
109 | Avoid doing this, | |
110 | since each zombie thread consumes some system resources, | |
111 | and when enough zombie threads have accumulated, | |
112 | it will no longer be possible to create new threads (or processes). | |
113 | ||
114 | There is no pthreads analog of | |
115 | .IR "waitpid(-1,\ &status,\ 0)" , | |
116 | that is, "join with any terminated thread". | |
117 | If you believe you need this functionality, | |
118 | you probably need to rethink your application design. | |
119 | ||
120 | All of the threads in a process are peers: | |
121 | any thread can join with any other thread in the process. | |
122 | .SH EXAMPLE | |
123 | See | |
124 | .BR pthread_create (3). | |
125 | .SH SEE ALSO | |
126 | .BR pthread_cancel (3), | |
127 | .BR pthread_create (3), | |
128 | .BR pthread_detach (3), | |
129 | .BR pthread_exit (3), | |
33a5ffc9 | 130 | .BR pthread_tryjoin_np (3), |
ebdd7ee1 | 131 | .BR pthreads (7) |