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 .