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VOP_LOCK(9)	       FreeBSD Kernel Developer's Manual	   VOP_LOCK(9)

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

SYNOPSIS
     #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);

DESCRIPTION
     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 call-
	    ing	VOP_LOCK() directly.  vn_lock()	also does not want a thread
	    specified as argument but it assumes curthread to be used.

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

SEE ALSO
     vnode(9)

AUTHORS
     This manual page was written by Doug Rabson.

FreeBSD	10.1		       February	25, 2008		  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | AUTHORS

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