MLOCK(P)						     POSIX Programmer's Manual							  MLOCK(P)

NAME

       mlock, munlock - lock or unlock a range of process address space (REALTIME)

SYNOPSIS

       #include <sys/mman.h>

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

DESCRIPTION

       The  mlock()  function  shall  cause those whole pages containing any part of the address space of the process starting at address addr and
       continuing for len bytes to be memory-resident until unlocked or until the process exits or execs another process image. The implementation
       may require that addr be a multiple of {PAGESIZE}.

       The  munlock() function shall unlock those whole pages containing any part of the address space of the process starting at address addr and
       continuing for len bytes, regardless of how many times mlock() has been called by the process for any of the pages in the specified  range.
       The implementation may require that addr be a multiple of {PAGESIZE}.

       If  any	of  the  pages in the range specified to a call to munlock() are also mapped into the address spaces of other processes, any locks
       established on those pages by another process are unaffected by the call of this process to munlock().  If any of the pages  in	the  range
       specified  by  a call to munlock() are also mapped into other portions of the address space of the calling process outside the range speci-
       fied, any locks established on those pages via the other mappings are also unaffected by this call.

       Upon successful return from mlock(), pages in the specified range  shall  be  locked  and  memory-resident.  Upon  successful  return  from
       munlock(),  pages  in the specified range shall be unlocked with respect to the address space of the process.  Memory residency of unlocked
       pages is unspecified.

       The appropriate privilege is required to lock process memory with mlock().

RETURN VALUE

       Upon successful completion, the mlock() and munlock() functions shall return a value of zero. Otherwise, no change is made to any locks	in
       the address space of the process, and the function shall return a value of -1 and set errno to indicate the error.

ERRORS

       The mlock() and munlock() functions shall fail if:

       ENOMEM Some  or	all  of the address range specified by the addr and len arguments does not correspond to valid mapped pages in the address
	      space of the process.

       The mlock() function shall fail if:

       EAGAIN Some or all of the memory identified by the operation could not be locked when the call was made.

       The mlock() and munlock() functions may fail if:

       EINVAL The addr argument is not a multiple of {PAGESIZE}.

       The mlock() function may fail if:

       ENOMEM Locking the pages mapped by the specified range 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() , mlockall() , 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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								  MLOCK(P)