munlock - reenable paging for some parts of memory


SYNOPSIS

       #include <sys/mman.h>

       int munlock(const void *addr, size_t len);


DESCRIPTION

       munlock  reenables  paging  for  the  memory  in the range
       starting at addr with length len bytes.  All  pages  which
       contain  a  part  of  the specified memory range can after
       calling munlock be moved to external swap space  again  by
       the kernel.

       Memory  locks  do  not  stack, i.e., pages which have been
       locked several times by calls to mlock or mlockall will be
       unlocked by a single call to munlock for the corresponding
       range or by munlockall.  Pages which are mapped to several
       locations  or by several processes stay locked into RAM as
       long as they are locked at least at one location or by  at
       least one process.

       On POSIX systems on which mlock and munlock are available,
       _POSIX_MEMLOCK_RANGE is  defined  in  <unistd.h>  and  the
       value  PAGESIZE  from  <limits.h>  indicates the number of
       bytes per page.


RETURN VALUE

       On  success,  munlock  returns  zero.   On  error,  -1  is
       returned,  errno  is set appropriately, and no changes are
       made to any locks in the address space of the process.


ERRORS

       ENOMEM Some of the specified address range does not corre­
              spond  to  mapped pages in the address space of the
              process.

       EINVAL len was not a positive number.


CONFORMING TO

       POSIX.1b, SVr4


SEE ALSO

       mlock(2), mlockall(2), munlockall(2)