1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 1996 Doug Rabson 4.\" 5.\" All rights reserved. 6.\" 7.\" This program is free software. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 19.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28.\" 29.\" $FreeBSD$ 30.\" 31.Dd July 24, 1996 32.Os 33.Dt VOP_LOCK 9 34.Sh NAME 35.Nm VOP_LOCK , 36.Nm VOP_UNLOCK , 37.Nm VOP_ISLOCKED , 38.Nm vn_lock 39.Nd serialize access to a vnode 40.Sh SYNOPSIS 41.In sys/param.h 42.In sys/lock.h 43.In sys/vnode.h 44.Ft int 45.Fn VOP_LOCK "struct vnode *vp" "int flags" "struct thread *td" 46.Ft int 47.Fn VOP_UNLOCK "struct vnode *vp" "int flags" "struct thread *td" 48.Ft int 49.Fn VOP_ISLOCKED "struct vnode *vp" "struct thread *td" 50.Ft int 51.Fn vn_lock "struct vnode *vp" "int flags" "struct thread *td" 52.Sh DESCRIPTION 53These calls are used to serialize access to the file system, such as 54to prevent two writes to the same file from happening at the 55same time. 56.Pp 57The arguments are: 58.Bl -tag -width flags 59.It Fa vp 60The vnode being locked or unlocked. 61.It Fa flags 62One of the lock request types: 63.Pp 64.Bl -tag -width ".Dv LK_EXCLUPGRADE" -offset indent -compact 65.It Dv LK_SHARED 66Shared lock. 67.It Dv LK_EXCLUSIVE 68Exclusive lock. 69.It Dv LK_UPGRADE 70Shared-to-exclusive upgrade. 71.It Dv LK_EXCLUPGRADE 72First shared-to-exclusive upgrade. 73.It Dv LK_DOWNGRADE 74Exclusive-to-shared downgrade. 75.It Dv LK_RELEASE 76Release any type of lock. 77.It Dv LK_DRAIN 78Wait for all lock activity to end. 79.El 80.Pp 81The lock type may be 82.Em or Ns 'ed 83with these lock flags: 84.Pp 85.Bl -tag -width ".Dv LK_EXCLUPGRADE" -offset indent -compact 86.It Dv LK_NOWAIT 87Do not sleep to wait for lock. 88.It Dv LK_SLEEPFAIL 89Sleep, then return failure. 90.It Dv LK_CANRECURSE 91Allow recursive exclusive lock. 92.It Dv LK_REENABLE 93Lock is to be reenabled after drain. 94.It Dv LK_NOPAUSE 95No spinloop. 96.El 97.Pp 98The lock type may be 99.Em or Ns 'ed 100with these control flags: 101.Pp 102.Bl -tag -width ".Dv LK_EXCLUPGRADE" -offset indent -compact 103.It Dv LK_INTERLOCK 104Specify when the caller already has a simple lock 105.Fn ( VOP_LOCK 106will unlock the simple lock after getting the lock). 107.It Dv LK_RETRY 108Retry until locked. 109.It Dv LK_NOOBJ 110Do not create object. 111.El 112.It Fa td 113Thread context to use for the locks. 114.El 115.Pp 116Kernel code should use 117.Fn vn_lock 118to lock a vnode rather than calling 119.Fn VOP_LOCK 120directly. 121.Sh RETURN VALUES 122Zero is returned on success, otherwise an error is returned. 123.Sh PSEUDOCODE 124.Bd -literal 125struct vopnode { 126 int von_flag; 127 /* 128 * Other file system specific data. 129 */ 130 ...; 131}; 132#define VON_LOCKED 1 133#define VON_WANTED 2 134#define VTOVON(vp) ((struct vopnode *) (vp)->v_data) 135 136int 137vop_lock(struct vnode *vp) 138{ 139 struct vopnode* vop; 140 141start: 142 while (vp->v_flag & VXLOCK) { 143 vp->v_flag |= VXWANT; 144 tsleep((caddr_t)vp, PINOD, "voplk1", 0); 145 } 146 if (vp->v_tag == VT_NON) 147 return ENOENT; 148 149 vop = VTOVON(vp); 150 if (vop->von_flag & VON_LOCKED) { 151 vop->von_flag |= VON_WANTED; 152 tsleep((caddr_t) vop, PINOD, "voplk2", 0); 153 goto start; 154 } 155 156 vop->von_flag |= VON_LOCKED; 157 158 return 0; 159} 160 161int 162vop_unlock(struct vnode *vp) 163{ 164 struct vopnode *vop = VTOVON(vp); 165 166 if ((vop->von_flag & VON_LOCKED) == 0) { 167 panic("vop_unlock not locked"); 168 } 169 vop->von_flag &= ~VON_LOCKED; 170 if (vop->von_flag & VON_WANTED) { 171 vop->von_flag &= ~VON_WANTED; 172 wakeup((caddr_t) vop); 173 } 174 175 return 0; 176} 177 178int 179vop_islocked(struct vnode *vp) 180{ 181 struct vopnode *vop = VTOVON(vp); 182 183 if (vop->von_flag & VON_LOCKED) 184 return 1; 185 else 186 return 0; 187} 188.Ed 189.Sh SEE ALSO 190.Xr vnode 9 191.Sh AUTHORS 192This manual page was written by 193.An Doug Rabson . 194