HP-UX Reference (11i v2 04/09) - 2 System Calls (vol 5)

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munlock(2) munlock(2)

NAME

munlock() - unlock a segment of the process virtual address space

SYNOPSIS

#include <sys/mman.h>

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

DESCRIPTION

The munlock() system call allows the calling process to unlock a segment of the process virtual address

space that may have been previously locked with

mlock() or mlockall(). Upon successful comple-

tion of the

munlock(), pages within the speciﬁed segment are subject to routine paging and/or swap-

ping.

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.

Pages are unlocked at page boundaries that encompass the range from addr to addr + len. If any address

within the range is not a valid part of the process virtual address space, an error is returned and no

unlocks are performed. However, no error is reported for valid pages within the range that are not

already locked, since their state at the completion of the

munlock() call is as desired.

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.

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)).

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

munlock() returns the following values:

0 Successful completion.

-1 Failure. The requested operation is not performed. errno is set to indicate the error.

ERRORS

munlock() 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.

[EINVAL] The

len parameter was zero.

[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

munlock() unlocks the ﬁrst 10 pages of the calling process address space:

munlock(sbrk(0), 40960);