1MLOCK(3P) POSIX Programmer's Manual MLOCK(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 mlock, munlock — lock or unlock a range of process address space (REAL‐
14 TIME)
15
17 #include <sys/mman.h>
18 int mlock(const void *addr, size_t len);
20 int munlock(const void *addr, size_t len);
21
23 The mlock() function shall cause those whole pages containing any part
24 of the address space of the process starting at address addr and con‐
25 tinuing for len bytes to be memory-resident until unlocked or until the
26 process exits or execs another process image. The implementation may
27 require that addr be a multiple of {PAGESIZE}.
28 The munlock() function shall unlock those whole pages containing any
30 part of the address space of the process starting at address addr and
31 continuing for len bytes, regardless of how many times mlock() has been
32 called by the process for any of the pages in the specified range. The
33 implementation may require that addr be a multiple of {PAGESIZE}.
34 If any of the pages in the range specified to a call to munlock() are
36 also mapped into the address spaces of other processes, any locks
37 established on those pages by another process are unaffected by the
38 call of this process to munlock(). If any of the pages in the range
39 specified by a call to munlock() are also mapped into other portions of
40 the address space of the calling process outside the range specified,
41 any locks established on those pages via the other mappings are also
42 unaffected by this call.
43 Upon successful return from mlock(), pages in the specified range shall
45 be locked and memory-resident. Upon successful return from munlock(),
46 pages in the specified range shall be unlocked with respect to the
47 address space of the process. Memory residency of unlocked pages is
48 unspecified.
49 Appropriate privileges are required to lock process memory with
51 mlock().
52
54 Upon successful completion, the mlock() and munlock() functions shall
55 return a value of zero. Otherwise, no change is made to any locks in
56 the address space of the process, and the function shall return a value
57 of −1 and set errno to indicate the error.
58
60 The mlock() and munlock() functions shall fail if:
61 ENOMEM Some or all of the address range specified by the addr and len
63 arguments does not correspond to valid mapped pages in the
64 address space of the process.
65 The mlock() function shall fail if:
67 EAGAIN Some or all of the memory identified by the operation could not
69 be locked when the call was made.
70 The mlock() and munlock() functions may fail if:
72 EINVAL The addr argument is not a multiple of {PAGESIZE}.
74 The mlock() function may fail if:
76 ENOMEM Locking the pages mapped by the specified range would exceed an
78 implementation-defined limit on the amount of memory that the
79 process may lock.
80 EPERM The calling process does not have appropriate privileges to per‐
82 form the requested operation.
83 The following sections are informative.
85
87 None.
88
90 None.
91
93 None.
94
96 None.
97
99 exec, exit(), fork(), mlockall(), munmap()
100 The Base Definitions volume of POSIX.1‐2008, <sys_mman.h>
102
104 Portions of this text are reprinted and reproduced in electronic form
105 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
106 -- Portable Operating System Interface (POSIX), The Open Group Base
107 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
108 cal and Electronics Engineers, Inc and The Open Group. (This is
109 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
110 event of any discrepancy between this version and the original IEEE and
111 The Open Group Standard, the original IEEE and The Open Group Standard
112 is the referee document. The original Standard can be obtained online
113 at http://www.unix.org/online.html .
114 Any typographical or formatting errors that appear in this page are
116 most likely to have been introduced during the conversion of the source
117 files to man page format. To report such errors, see https://www.ker‐
118 nel.org/doc/man-pages/reporting_bugs.html .
119IEEE/The Open Group 2013 MLOCK(3P)