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MLOCK(3P) POSIX Programmer's Manual MLOCK(3P)
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.
mlock, munlock — lock or unlock a range of process address space
(REALTIME)
#include <sys/mman.h>
int mlock(const void *addr, size_t len);
int munlock(const void *addr, size_t len);
The mlock() function shall cause those whole pages containing any
part of the address space of the process starting at address addr and
continuing 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().
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.
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
perform the requested operation.
The following sections are informative.
None.
None.
None.
None.
exec(1p), exit(3p), fork(3p), mlockall(3p), munmap(3p)
The Base Definitions volume of POSIX.1‐2008, sys_mman.h(0p)
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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 MLOCK(3P)
Pages that refer to this page: sys_mman.h(0p), _Exit(3p), mlockall(3p), munlock(3p), munmap(3p)