Manual Pages  — VOP_LOCK

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

SYNOPSIS DESCRIPTION RETURN VALUES SEE ALSO AUTHORS

#include <sys/param.h>

#include <sys/lock.h>

#include <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.
LK_CANRECURSE
	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 Doug Rabson.