mlock.2 (2010 09)

m
mlock(2) mlock(2)
NAME
mlock() - lock a segment of the process virtual address space in memory
SYNOPSIS
#include <sys/mman.h>
int mlock( const void * addr, size_t len) ;
DESCRIPTION
The mlock() system call allows the calling process to lock a segment of the process virtual address
space into memory. Any addressable segment of the process’ address space may be locked. Locked seg-
ments are immune to all routine swapping.
addr must be a valid address in the process virtual address space. addr + len must also be a valid
address in the process virtual address space.
Locks are applied at page boundaries that encompass the range from addr to addr + len. If any address
within the range is not valid, an error is returned and no locks are applied.
munlock() or munlockall() can be used to unlock memory segments (or all memory segments)
locked with mlock().
Regardless of how many times a process locks a page, a single
munlock() or munlockall() will
unlock it. An munlock() of a page within a range specified in an mlock() call results in only the
range specified in the
munlock() being unlocked.
When memory is shared by multiple processes and mlocks are applied to the same physical page by mul-
tiple processes, a page remains locked until the last lock is removed from that page.
Locks applied with
mlock() are not inherited by a child process.
The user must have the
MLOCK privilege.
Although
plock() and the mlock() family of functions may be used together in an application, each
may affect the other in unexpected ways. This practice is not recommended.
Security Restrictions
Some or all of the actions associated with this system call require the
MLOCK privilege. Processes owned
by the superuser have this privilege. Processes owned by other users may have this privilege, depending
on system configuration. See privileges (5) for more information about privileged access on systems that
support fine-grained privileges.
RETURN VALUE
mlock() returns the following values:
0 Successful completion.
-1 Failure. The requested operation is not performed. errno is set to indicate the error.
ERRORS
If
mlock() fails, errno is set to one of the following values:
[ENOMEM] One or more addresses in the specified range is not valid within the process address
space.
[EAGAIN] There is not enough lockable memory in the system to satisfy the locking request.
[EINVAL] The
len parameter was zero.
[EPERM] The user does not have the
MLOCK privilege.
EXAMPLES
The following call to
mlock() locks the first 10 pages of the calling process in memory:
mlock(sbrk(0), 40960);
SEE ALSO
setprivgrp(1M), getprivgrp(2), mlockall(2), munlock(2), munlockall(2), plock(2), privileges(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1