MLOCK(3P) POSIX Programmer's Manual MLOCK(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAME
mlock, munlock — lock or unlock a range of process address space (REAL‐
TIME)
SYNOPSIS
#include <sys/mman.h>
int mlock(const void *addr, size_t len);
int munlock(const void *addr, size_t len);
DESCRIPTION
The mlock() function shall cause those whole pages containing any part
of the address space of the process starting at address addr and con‐
tinuing for len bytes to be memory-resident until unlocked or until the
process exits or execs another process image. The implementation may
require that addr be a multiple of {PAGESIZE}.
The munlock() function shall unlock those whole pages containing any
part of the address space of the process starting at address addr and
continuing for len bytes, regardless of how many times mlock() has been
called by the process for any of the pages in the specified range. The
implementation may require that addr be a multiple of {PAGESIZE}.
If any of the pages in the range specified to a call to munlock() are
also mapped into the address spaces of other processes, any locks
established on those pages by another process are unaffected by the
call of this process to munlock(). If any of the pages in the range
specified by a call to munlock() are also mapped into other portions of
the address space of the calling process outside the range specified,
any locks established on those pages via the other mappings are also
unaffected by this call.
Upon successful return from mlock(), pages in the specified range shall
be locked and memory-resident. Upon successful return from munlock(),
pages in the specified range shall be unlocked with respect to the
address space of the process. Memory residency of unlocked pages is
unspecified.
Appropriate privileges are required to lock process memory with
mlock().
RETURN VALUE
Upon successful completion, the mlock() and munlock() functions shall
return a value of zero. Otherwise, no change is made to any locks in
the address space of the process, and the function shall return a value
of −1 and set errno to indicate the error.
ERRORS
The mlock() and munlock() functions shall fail if:
ENOMEM Some or all of the address range specified by the addr and len
arguments does not correspond to valid mapped pages in the
address space of the process.
The mlock() function shall fail if:
EAGAIN Some or all of the memory identified by the operation could not
be locked when the call was made.
The mlock() and munlock() functions may fail if:
EINVAL The addr argument is not a multiple of {PAGESIZE}.
The mlock() function may fail if:
ENOMEM Locking the pages mapped by the specified range would exceed an
implementation-defined limit on the amount of memory that the
process may lock.
EPERM The calling process does not have appropriate privileges to per‐
form the requested operation.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
exec, exit(), fork(), mlockall(), munmap()
The Base Definitions volume of POSIX.1‐2008, <sys_mman.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 MLOCK(3P)
