186 lines
4.4 KiB
Groff
186 lines
4.4 KiB
Groff
.\" -*- nroff -*-
|
|
.\"
|
|
.\" Copyright (c) 1996 Doug Rabson
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This program is free software.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd February 25, 2008
|
|
.Os
|
|
.Dt VOP_LOCK 9
|
|
.Sh NAME
|
|
.Nm VOP_LOCK ,
|
|
.Nm VOP_UNLOCK ,
|
|
.Nm VOP_ISLOCKED ,
|
|
.Nm vn_lock
|
|
.Nd serialize access to a vnode
|
|
.Sh SYNOPSIS
|
|
.In sys/param.h
|
|
.In sys/lock.h
|
|
.In sys/vnode.h
|
|
.Ft int
|
|
.Fn VOP_LOCK "struct vnode *vp" "int flags"
|
|
.Ft int
|
|
.Fn VOP_UNLOCK "struct vnode *vp" "int flags"
|
|
.Ft int
|
|
.Fn VOP_ISLOCKED "struct vnode *vp"
|
|
.Ft int
|
|
.Fn vn_lock "struct vnode *vp" "int flags"
|
|
.Sh DESCRIPTION
|
|
These calls are used to serialize access to the file system, such as
|
|
to prevent two writes to the same file from happening at the
|
|
same time.
|
|
.Pp
|
|
The arguments are:
|
|
.Bl -tag -width flags
|
|
.It Fa vp
|
|
The vnode being locked or unlocked.
|
|
.It Fa flags
|
|
One of the lock request types:
|
|
.Pp
|
|
.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact
|
|
.It Dv LK_SHARED
|
|
Shared lock.
|
|
.It Dv LK_EXCLUSIVE
|
|
Exclusive lock.
|
|
.It Dv LK_UPGRADE
|
|
Shared-to-exclusive upgrade.
|
|
.It Dv LK_DOWNGRADE
|
|
Exclusive-to-shared downgrade.
|
|
.It Dv LK_RELEASE
|
|
Release any type of lock.
|
|
.It Dv LK_DRAIN
|
|
Wait for all lock activity to end.
|
|
.El
|
|
.Pp
|
|
The lock type may be
|
|
.Em or Ns 'ed
|
|
with these lock flags:
|
|
.Pp
|
|
.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact
|
|
.It Dv LK_NOWAIT
|
|
Do not sleep to wait for lock.
|
|
.It Dv LK_SLEEPFAIL
|
|
Sleep, then return failure.
|
|
.It Dv LK_CANRECURSE
|
|
Allow recursive exclusive lock.
|
|
.El
|
|
.Pp
|
|
The lock type may be
|
|
.Em or Ns 'ed
|
|
with these control flags:
|
|
.Pp
|
|
.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact
|
|
.It Dv LK_INTERLOCK
|
|
Specify when the caller already has a simple lock
|
|
.Fn ( VOP_LOCK
|
|
will unlock the simple lock after getting the lock).
|
|
.It Dv LK_RETRY
|
|
Retry until locked.
|
|
.El
|
|
.Pp
|
|
Kernel code should use
|
|
.Fn vn_lock
|
|
to lock a vnode rather than calling
|
|
.Fn VOP_LOCK
|
|
directly.
|
|
.Fn vn_lock
|
|
also does not want a thread specified as argument but it
|
|
assumes curthread to be used.
|
|
.Sh RETURN VALUES
|
|
Zero is returned on success, otherwise an error is returned.
|
|
.Sh PSEUDOCODE
|
|
.Bd -literal
|
|
struct vopnode {
|
|
int von_flag;
|
|
/*
|
|
* Other file system specific data.
|
|
*/
|
|
...;
|
|
};
|
|
#define VON_LOCKED 1
|
|
#define VON_WANTED 2
|
|
#define VTOVON(vp) ((struct vopnode *) (vp)->v_data)
|
|
|
|
int
|
|
vop_lock(struct vnode *vp)
|
|
{
|
|
struct vopnode* vop;
|
|
|
|
start:
|
|
while (vp->v_flag & VXLOCK) {
|
|
vp->v_flag |= VXWANT;
|
|
tsleep((caddr_t)vp, PINOD, "voplk1", 0);
|
|
}
|
|
if (vp->v_tag == VT_NON)
|
|
return ENOENT;
|
|
|
|
vop = VTOVON(vp);
|
|
if (vop->von_flag & VON_LOCKED) {
|
|
vop->von_flag |= VON_WANTED;
|
|
tsleep((caddr_t) vop, PINOD, "voplk2", 0);
|
|
goto start;
|
|
}
|
|
|
|
vop->von_flag |= VON_LOCKED;
|
|
|
|
return 0;
|
|
}
|
|
|
|
int
|
|
vop_unlock(struct vnode *vp)
|
|
{
|
|
struct vopnode *vop = VTOVON(vp);
|
|
|
|
if ((vop->von_flag & VON_LOCKED) == 0) {
|
|
panic("vop_unlock not locked");
|
|
}
|
|
vop->von_flag &= ~VON_LOCKED;
|
|
if (vop->von_flag & VON_WANTED) {
|
|
vop->von_flag &= ~VON_WANTED;
|
|
wakeup((caddr_t) vop);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int
|
|
vop_islocked(struct vnode *vp)
|
|
{
|
|
struct vopnode *vop = VTOVON(vp);
|
|
|
|
if (vop->von_flag & VON_LOCKED)
|
|
return 1;
|
|
else
|
|
return 0;
|
|
}
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr vnode 9
|
|
.Sh AUTHORS
|
|
This manual page was written by
|
|
.An Doug Rabson .
|