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
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.