mctl(3)                                                         mctl(3)

  mctl()

  NAME

    mctl() - control memory management

  SYNOPSIS

    #include 

    int mctl(void *addr, size_t len, int cmd, int arg)

  DESCRIPTION

    The mctl(3) call controls the management of memory for the pages mapped in
    the range [addr, addr + len]. The actual management command is specified
    by cmd, which can be one of:

    MC_LOCK
        Lock the pages in the range that have the specified attributes.
        Although different mappings may cause the same page to be locked more
        than once, the locks do not nest within a particular mapping. One
        unlock operation undoes all the locks held on a page by a process, but
        locks held by aanother process are held in memory until the locking
        process has released the lock. (If a locked page is removed or
        deleted, that implicitly unlocks it.)
        The value of arg must be 0.

    MC_LOCKAS
        Lock the pages in the address space that have the specified
        attributes. In this case, the arg value controls whether the locked
        pages are mapped in the current address space or ones that will be
        mapped later, or both.

    Values that can be ORed into arg are:

    MCL_CURRENT
        Lock the current mappings

    MCL_FUTURE
        Lock all mappings added to the address space, so long as there is
        sufficient memory

    MC_UNLOCK
        Unlock all of the pages in the range that have the specified
        attributes. The value of arg must be 0.

    MC_UNLOCKAS
        Unlock any locks on the address space (MC_LOCKAS) and remove locks on
        all pages in the address space that have the specified attributes.

    The mctl(3) call is actually an historical version of memcntl(2); it is
    equivalent to:

    memcntl(addr, len, cmd, (void *)arg,
    PROT_READ|PROT_WRITE|PROT_EXEC|SHARED|PRIVATE , 0)

    See the memcntl(2) man page for more information.

  RETURN VALUES

    The mctl(3) call returns 0 on success and -1 on failure. On failure, it
    sets the value of errno to indicate the error.

  ERRORS

    The mctl(3) call can fail for the following reasons:

    [EAGAIN]
        Insufficient resources to lock some or all of the memory.

    [EBUSY]
        One of the pages is locked in memory and MS_INVALIDATE was the
        command.

    [EINVAL]
        The addr is invalid. It must be a multiple of the page size.

    [EIO]
        An I/O error occurred.

    [ENOMEM]
        The addresses in the range are not valid for the address space of the
        process, or are for pages that aren't mapped.

    [EPERM]
        A locking command was specified and the effective user ID does not
        have appropriate privileges.

  SEE ALSO

    memcntl(2)

  USAGE NOTES

    The mctl function is thread safe.

    The mctl function is not async-signal safe.