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

       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 address space of the process shall be memory-resident and
       locked.  Upon return from the munlockall() function, all currently  mapped  pages  of  the
       address  space  of  the process shall be unlocked with respect to the address space of the
       process.  The memory residency of unlocked pages is unspecified.

       Appropriate privileges are 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 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(), mlock(), munmap()

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

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 .