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
12 mlock, munlock — lock or unlock a range of process address space (REAL‐
13 TIME)
14
16 #include <sys/mman.h>
17 int mlock(const void *addr, size_t len);
19 int munlock(const void *addr, size_t len);
20
22 The mlock() function shall cause those whole pages containing any part
23 of the address space of the process starting at address addr and con‐
24 tinuing for len bytes to be memory-resident until unlocked or until the
25 process exits or execs another process image. The implementation may
26 require that addr be a multiple of {PAGESIZE}.
27 The munlock() function shall unlock those whole pages containing any
29 part of the address space of the process starting at address addr and
30 continuing for len bytes, regardless of how many times mlock() has been
31 called by the process for any of the pages in the specified range. The
32 implementation may require that addr be a multiple of {PAGESIZE}.
33 If any of the pages in the range specified to a call to munlock() are
35 also mapped into the address spaces of other processes, any locks
36 established on those pages by another process are unaffected by the
37 call of this process to munlock(). If any of the pages in the range
38 specified by a call to munlock() are also mapped into other portions of
39 the address space of the calling process outside the range specified,
40 any locks established on those pages via the other mappings are also
41 unaffected by this call.
42 Upon successful return from mlock(), pages in the specified range shall
44 be locked and memory-resident. Upon successful return from munlock(),
45 pages in the specified range shall be unlocked with respect to the
46 address space of the process. Memory residency of unlocked pages is
47 unspecified.
48 Appropriate privileges are required to lock process memory with
50 mlock().
51
53 Upon successful completion, the mlock() and munlock() functions shall
54 return a value of zero. Otherwise, no change is made to any locks in
55 the address space of the process, and the function shall return a value
56 of -1 and set errno to indicate the error.
57
59 The mlock() and munlock() functions shall fail if:
60 ENOMEM Some or all of the address range specified by the addr and len
62 arguments does not correspond to valid mapped pages in the
63 address space of the process.
64 The mlock() function shall fail if:
66 EAGAIN Some or all of the memory identified by the operation could not
68 be locked when the call was made.
69 The mlock() and munlock() functions may fail if:
71 EINVAL The addr argument is not a multiple of {PAGESIZE}.
73 The mlock() function may fail if:
75 ENOMEM Locking the pages mapped by the specified range would exceed an
77 implementation-defined limit on the amount of memory that the
78 process may lock.
79 EPERM The calling process does not have appropriate privileges to per‐
81 form the requested operation.
82 The following sections are informative.
84
86 None.
87
89 None.
90
92 None.
93
95 None.
96
98 exec, exit(), fork(), mlockall(), munmap()
99 The Base Definitions volume of POSIX.1‐2017, <sys_mman.h>
101
103 Portions of this text are reprinted and reproduced in electronic form
104 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
105 table Operating System Interface (POSIX), The Open Group Base Specifi‐
106 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
107 Electrical and Electronics Engineers, Inc and The Open Group. In the
108 event of any discrepancy between this version and the original IEEE and
109 The Open Group Standard, the original IEEE and The Open Group Standard
110 is the referee document. The original Standard can be obtained online
111 at http://www.opengroup.org/unix/online.html .
112 Any typographical or formatting errors that appear in this page are
114 most likely to have been introduced during the conversion of the source
115 files to man page format. To report such errors, see https://www.ker‐
116 nel.org/doc/man-pages/reporting_bugs.html .
117IEEE/The Open Group 2017 MLOCK(3P)