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 munlockall().

       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 residency 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, Copyright (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.opengroup.org/unix/online.html .