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



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

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 .



IEEE/The Open Group                  2017                          MLOCKALL(3)
