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  calling  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.

Debian                                          February 25, 2008                                    VOP_LOCK(9)