PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

MLOCK(3P)                 POSIX Programmer's Manual                MLOCK(3P)

PROLOG         top

       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         top

       mlock, munlock — lock or unlock a range of process address space
       (REALTIME)

SYNOPSIS         top

       #include <sys/mman.h>

       int mlock(const void *addr, size_t len);
       int munlock(const void *addr, size_t len);

DESCRIPTION         top

       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().

RETURN VALUE         top

       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         top

       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.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       exec(1p), exit(3p), fork(3p), mlockall(3p), munmap(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_mman.h(0p)

COPYRIGHT         top

       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)