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