MLOCK(3C) | Standard C Library Functions | MLOCK(3C) |
mlock
, munlock
—
#include <sys/mman.h>
int
mlock
(const void *addr,
size_t len);
int
munlock
(const void *addr,
size_t len);
mlock
() function uses the mappings established for
the address range [addr, addr +
len) to identify pages to be locked in memory. If the
page identified by a mapping changes, such as occurs when a copy of a writable
MAP_PRIVATE
page is made upon the first store, the
lock will be transferred to the newly copied private page.
The munlock
() function removes locks
established with mlock
().
A given page may be locked multiple times by executing an
mlock
() through different mappings. That is, if two
different processes lock the same page, then the page will remain locked
until both processes remove their locks. However, within a given mapping,
page locks do not nest — multiple mlock
()
operations on the same address in the same process will all be removed with
a single munlock
(). Of course, a page locked in one
process and mapped in another (or visible through a different mapping in the
locking process) is still locked in memory. This fact can be used to create
applications that do nothing other than lock important data in memory,
thereby avoiding page I/O faults on references from other processes in the
system.
The contents of the locked pages will not be transferred to or from disk except when explicitly requested by one of the locking processes. This guarantee applies only to the mapped data, and not to any associated data structures (file descriptors and on-disk metadata, among others).
If the mapping through which an mlock
()
has been performed is removed, an munlock
() is
implicitly performed. An munlock
() is also performed
implicitly when a page is deleted through file removal or truncation.
Locks established with mlock
() are not
inherited by a child process after a
fork(2) and are not nested.
Attempts to mlock
() more memory than a
system-specific limit will fail.
mlock
() and
munlock
() functions return 0.
Otherwise, no changes are made to any locks in the address space of the
process, the functions return -1 and set
errno to indicate the error.
mlock
() and munlock
()
functions will fail if:
EINVAL
ENOMEM
ENOSYS
EPERM
The mlock
() function will fail if:
EAGAIN
mlock
() and munlock
() is
restricted to users with the {PRIV_PROC_LOCK_MEMORY} privilege.
March 13, 2022 | OmniOS |