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



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       mlockall, munlockall - lock/unlock the address space of a process (REALTIME)

SYNOPSIS
       #include <sys/mman.h>

       int mlockall(int flags);
       int munlockall(void);


DESCRIPTION
       The mlockall() function shall cause all of the pages mapped by the address space of a process to be memory-resident until
       unlocked or until the process exits or execs another process image. The flags argument determines whether the pages to be
       locked  are those currently mapped by the address space of the process, those that are mapped in the future, or both. The
       flags argument is constructed from the bitwise-inclusive OR of one or more of the following symbolic  constants,  defined
       in <sys/mman.h>:

       MCL_CURRENT
              Lock all of the pages currently mapped into the address space of the process.

       MCL_FUTURE
              Lock  all of the pages that become mapped into the address space of the process in the future, when those mappings
              are established.


       If MCL_FUTURE is specified, and the automatic locking of future mappings eventually causes the amount of locked memory to
       exceed the amount of available physical memory or any other implementation-defined limit, the behavior is implementation-
       defined. The manner in which the implementation informs the application  of  these  situations  is  also  implementation-
       defined.

       The  munlockall()  function  shall  unlock all currently mapped pages of the address space of the process. Any pages that
       become mapped into the address space of the process after a call to munlockall() shall not be locked, unless there is  an
       intervening  call to mlockall() specifying MCL_FUTURE or a subsequent call to mlockall() specifying MCL_CURRENT. If pages
       mapped into the address space of the process are also mapped into the address spaces of other processes and are locked by
       those  processes,  the locks established by the other processes shall be unaffected by a call by this process to munlock-
       all().

       Upon successful return from the mlockall() function that  specifies  MCL_CURRENT,  all  currently  mapped  pages  of  the
       process'  address  space  shall  be memory-resident and locked. Upon return from the munlockall() function, all currently
       mapped pages of the process' address space shall be unlocked with respect to the process' address space. The memory resi-
       dency of unlocked pages is unspecified.

       The appropriate privilege is required to lock process memory with mlockall().

RETURN VALUE
       Upon  successful  completion, the mlockall() function shall return a value of zero. Otherwise, no additional memory shall
       be locked, and the function shall return a value of -1 and set errno to indicate the error.  The  effect  of  failure  of
       mlockall() on previously existing locks in the address space is unspecified.

       If  it  is supported by the implementation, the munlockall() function shall always return a value of zero. Otherwise, the
       function shall return a value of -1 and set errno to indicate the error.

ERRORS
       The mlockall() function shall fail if:

       EAGAIN Some or all of the memory identified by the operation could not be locked when the call was made.

       EINVAL The flags argument is zero, or includes unimplemented flags.


       The mlockall() function may fail if:

       ENOMEM Locking all of the pages currently mapped into the address space of the process would  exceed  an  implementation-
              defined limit on the amount of memory that the process may lock.

       EPERM  The calling process does not have the appropriate privilege 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(), mlock(), munmap(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/mman.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                  MLOCKALL(3P)