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    Length: 1511 (0x5e7)
    Types: TextFile
    Notes: UNIX file
    Names: »vlock.2v«

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        └─⟦this⟧ »usr/man/man2/vlock.2v« 

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	@(#)vlock.2v	2.1	7/1/84
	@(#)Copyright (C) 1983 by National Semiconductor Corp.
..
.TH VLOCK 2V
.SH NAME
vlock \- lock process pages into memory
.SH SYNOPSIS
.nf
.B vlock(function, address)
.B char *address;
.fi
.SH DESCRIPTION
.I Vlock
is used to lock or unlock a page (1024 bytes) of a process in memory.
Locked pages cannot be swapped or moved around in memory, even if the
process is not runnable.  This capability is useful when talking to
peripherals which need to do DMA into memory, or if very fast response
times are required.
.I Function
is 0 to unlock a page, and 1 to lock a page.
.I Address
is the address of the page to be locked or unlocked.  If the page is
successfully locked,
.I vlock
returns the physical address of the page in memory.
.PP
Pages of a process which are not locked are swappable.  If the process does a
.IR fork (2),
the parent's locked pages will still be locked.  Shared text pages will also
be locked for the child process.  However, pages in the data or stack segment
of the child will not be locked.  An
.IR exec (2)
or
.IR exit (2)
unlocks all the pages of the process.  The
.I vlock
call is restricted to the super-user.  It is never necessary to lock pages
that have been mapped using
.IR vspy (2V).
.PP
.SH "SEE ALSO"
vspy(2V), nice(2)
.SH DIAGNOSTICS
-1 is returned if any argument is invalid, or if the user is not privileged.
.SH BUGS
The system does not check to see how many pages are locked.  Thus the
system can crash if not enough swappable pages remain.