mlock(3p) — Linux manual page

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
       (REALTIME)

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 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

       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 perform the requested operation.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

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

       The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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.opengroup.org/unix/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               2017                         MLOCK(3P)

Pages that refer to this page: sys_mman.h(0p), _Exit(3p), mlockall(3p), munlock(3p), munmap(3p)

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