oracular (3) mlock.3posix.gz

Provided by: manpages-posix-dev_2017a-2_all bug

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, exit(), fork(), mlockall(), munmap()

       The Base Definitions volume of POSIX.1‐2017, <sys_mman.h>


       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 .