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 August 23, 2022 32.Dt VOP_LOCK 9 33.Os 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" 46.Ft int 47.Fn VOP_UNLOCK "struct vnode *vp" 48.Ft int 49.Fn VOP_ISLOCKED "struct vnode *vp" 50.Ft int 51.Fn vn_lock "struct vnode *vp" "int flags" 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_CANRECURSE" -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_DOWNGRADE 72Exclusive-to-shared downgrade. 73.It Dv LK_RELEASE 74Release any type of lock. 75.It Dv LK_DRAIN 76Wait for all lock activity to end. 77.El 78.Pp 79The lock type may be 80.Em or Ns 'ed 81with these lock flags: 82.Pp 83.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact 84.It Dv LK_NOWAIT 85Do not sleep to wait for lock. 86.It Dv LK_SLEEPFAIL 87Sleep, then return failure. 88.It Dv LK_CANRECURSE 89Allow recursive exclusive lock. 90.It Dv LK_NOWITNESS 91Instruct 92.Xr witness 4 93to ignore this instance. 94.El 95.Pp 96The lock type may be 97.Em or Ns 'ed 98with these control flags: 99.Pp 100.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact 101.It Dv LK_INTERLOCK 102Specify when the caller already has a simple lock 103.Po Fn VOP_LOCK 104will unlock the simple lock after getting the lock 105.Pc . 106.It Dv LK_RETRY 107Retry until locked. 108.El 109.Pp 110Kernel code should use 111.Fn vn_lock 112to lock a vnode rather than calling 113.Fn VOP_LOCK 114directly. 115.Fn vn_lock 116also does not want a thread specified as argument but it 117assumes curthread to be used. 118.El 119.Sh RETURN VALUES 120Zero is returned on success, otherwise an error is returned. 121.Sh SEE ALSO 122.Xr vnode 9 123.Sh AUTHORS 124This manual page was written by 125.An Doug Rabson . 126