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.Dd August 23, 2022 30.Dt VOP_LOCK 9 31.Os 32.Sh NAME 33.Nm VOP_LOCK , 34.Nm VOP_UNLOCK , 35.Nm VOP_ISLOCKED , 36.Nm vn_lock 37.Nd serialize access to a vnode 38.Sh SYNOPSIS 39.In sys/param.h 40.In sys/lock.h 41.In sys/vnode.h 42.Ft int 43.Fn VOP_LOCK "struct vnode *vp" "int flags" 44.Ft int 45.Fn VOP_UNLOCK "struct vnode *vp" 46.Ft int 47.Fn VOP_ISLOCKED "struct vnode *vp" 48.Ft int 49.Fn vn_lock "struct vnode *vp" "int flags" 50.Sh DESCRIPTION 51These calls are used to serialize access to the file system, such as 52to prevent two writes to the same file from happening at the 53same time. 54.Pp 55The arguments are: 56.Bl -tag -width flags 57.It Fa vp 58The vnode being locked or unlocked. 59.It Fa flags 60One of the lock request types: 61.Pp 62.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact 63.It Dv LK_SHARED 64Shared lock. 65.It Dv LK_EXCLUSIVE 66Exclusive lock. 67.It Dv LK_UPGRADE 68Shared-to-exclusive upgrade. 69.It Dv LK_DOWNGRADE 70Exclusive-to-shared downgrade. 71.It Dv LK_RELEASE 72Release any type of lock. 73.It Dv LK_DRAIN 74Wait for all lock activity to end. 75.El 76.Pp 77The lock type may be 78.Em or Ns 'ed 79with these lock flags: 80.Pp 81.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact 82.It Dv LK_NOWAIT 83Do not sleep to wait for lock. 84.It Dv LK_SLEEPFAIL 85Sleep, then return failure. 86.It Dv LK_CANRECURSE 87Allow recursive exclusive lock. 88.It Dv LK_NOWITNESS 89Instruct 90.Xr witness 4 91to ignore this instance. 92.El 93.Pp 94The lock type may be 95.Em or Ns 'ed 96with these control flags: 97.Pp 98.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact 99.It Dv LK_INTERLOCK 100Specify when the caller already has a simple lock 101.Po Fn VOP_LOCK 102will unlock the simple lock after getting the lock 103.Pc . 104.It Dv LK_RETRY 105Retry until locked. 106.El 107.Pp 108Kernel code should use 109.Fn vn_lock 110to lock a vnode rather than calling 111.Fn VOP_LOCK 112directly. 113.Fn vn_lock 114also does not want a thread specified as argument but it 115assumes curthread to be used. 116.El 117.Sh RETURN VALUES 118Zero is returned on success, otherwise an error is returned. 119.Sh SEE ALSO 120.Xr vnode 9 121.Sh AUTHORS 122This manual page was written by 123.An Doug Rabson . 124