NAME
plock() — lock process, text, data, stack, or shared library in memory
SYNOPSIS
#include <sys/lock.h>
int plock(int op);
DESCRIPTION
The
plock()
system call allows the calling process to lock
the text segment of the process (text lock),
its data segment (data lock),
or both its text and data segment (process lock) into memory.
Stack segments are also locked when data segments are locked.
Shared library text and shared library data segments (shlib lock)
can also be locked.
Locked segments are immune to all routine swapping.
plock()
also allows these segments to be unlocked.
The effective user ID of the calling process
must be a superuser or the user must be a member of a group
that has the MLOCK privilege (see
getprivgrp(2)
and
setprivgrp(1M)).
op
must be one of the following:
- PROCLOCK
Lock text and data segments into memory (process lock)
- TXTLOCK
Lock text segment into memory (text lock)
- DATLOCK
Lock data segment into memory (data lock)
- UNLOCK
Remove locks
- SHLIBLOCK
Lock shared library text and shared library data segments (shared library lock)
- PROCSHLIBLOCK
Lock text, data and shared library text and shared library data segments
into memory (process and shared library lock)
- TXTSHLIBLOCK
Lock text, shared library text and shared library data segments into memory
(text and shared library lock)
- DATSHLIBLOCK
Lock data, shared library text and shared library data segments into memory
(data and shared library lock)
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.
RETURN VALUE
plock()
returns the following values:
- 0
Successful completion.
- -1
Failure.
The requested operation is not performed.
errno
is set to indicate the error.
ERRORS
If
plock()
fails,
errno
is set to one of the following values.
- [EINVAL]
op
is equal to
PROCLOCK
and a process lock, a text lock, or a data lock
already exists on the calling process.
- [EINVAL]
op
is equal to
TXTLOCK
and a text lock or process lock already exists on the calling process.
- [EINVAL]
op
is equal to
DATLOCK
and a data lock, or process lock already exists on the calling process.
- [EINVAL]
op
is equal to
UNLOCK
and no type of lock exists on the calling process.
- [EINVAL]
op
is equal to
SHLIBLOCK
and there are no unlocked shared library segments in the calling process.
- [EINVAL]
op
is equal to
PROCSHLIBLOCK
and a process lock, a text lock, or a data lock
already exists on the calling process.
- [EINVAL]
op
is equal to
TXTSHLIBLOCK
and a text lock or process lock already exists on the calling process.
- [EINVAL]
op
is equal to
DATSHLIBLOCK
and a data lock, or process lock already exists on the calling process.
- [EINVAL]
op
is not equal to one of the values specified in
DESCRIPTION.
- [EINVAL]
plock()
is not allowed in a
[vfork,exec]
window.
See
vfork(2).
- [ENOMEM]
There is not enough lockable memory in the system
to satisfy the locking request.
- [EPERM]
The effective user ID of the calling process
is not a superuser
and the user does not belong to a group that has the
MLOCK
privilege.
EXAMPLES
The following call to
plock()
locks the calling process in memory:
STANDARDS CONFORMANCE
plock(): SVID2, SVID3, XPG2
