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February 25, 2008


Manual pages for a GNU/kFreeBSD system


VOP_LOCK, VOP_UNLOCK, VOP_ISLOCKED, vn_lock - serialize access to a vnode


.In sys/param.h
.In sys/lock.h
.In sys/vnode.h int VOP_LOCK struct vnode *vp int flags int VOP_UNLOCK struct vnode *vp int flags int VOP_ISLOCKED struct vnode *vp int vn_lock struct vnode *vp int flags


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.
The arguments are:
vp The vnode being locked or unlocked.
flags One of the lock request types:
LK_SHARED Shared lock.
LK_EXCLUSIVE Exclusive lock.
LK_UPGRADE Shared-to-exclusive upgrade.
LK_DOWNGRADE Exclusive-to-shared downgrade.
LK_RELEASE Release any type of lock.
LK_DRAIN Wait for all lock activity to end.
The lock type may be or ’ed with these lock flags:
LK_NOWAIT Do not sleep to wait for lock.
LK_SLEEPFAIL Sleep, then return failure.
Allow recursive exclusive lock.
LK_NOWITNESS Instruct witness(4) to ignore this instance.
The lock type may be or ’ed with these control flags:
LK_INTERLOCK Specify when the caller already has a simple lock (VOP_LOCK will unlock the simple lock after getting the lock ).
LK_RETRY Retry until locked.
Kernel code should use vn_lock to lock a vnode rather than calling VOP_LOCK directly. vn_lock also does not want a thread specified as argument but it assumes curthread to be used.


Zero is returned on success, otherwise an error is returned.



This manual page was written by
.An Doug Rabson .
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