VOP_LOCK(9) MidnightBSD 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, struct thread *td);
int
VOP_UNLOCK(struct vnode *vp, int flags, struct thread *td);
int
VOP_ISLOCKED(struct vnode *vp, struct thread *td);
int
vn_lock(struct vnode *vp, int flags, struct thread *td);
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_EXCLUPGRADE
First 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_REENABLE
Lock is to be reenabled after drain.
LK_NOPAUSE
No spinloop.
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.
LK_NOOBJ
Do not create object.
td
Thread context to use for the locks.
Kernel code should use vn_lock() to lock a vnode rather than calling VOP_LOCK() directly.
RETURN VALUES
Zero is returned on success, otherwise an error is returned.
PSEUDOCODE
struct vopnode {
int von_flag;
/*
* Other file system specific data.
*/
...;
};
|
#define VON_LOCKED |
1 |
|||
|
#define VON_WANTED |
2 |
|||
|
#define VTOVON(vp) |
((struct vopnode *) (vp)->v_data) |
int
vop_lock(struct vnode *vp)
{
struct vopnode* vop;
start:
while (vp->v_flag & VXLOCK) {
|
vp->v_flag |= VXWANT; |
|
|
tsleep((caddr_t)vp, PINOD, "voplk1", 0); |
}
if (vp->v_tag == VT_NON)
|
return ENOENT; |
vop = VTOVON(vp);
if (vop->von_flag & VON_LOCKED) {
|
vop->von_flag |= VON_WANTED; |
|
|
tsleep((caddr_t) vop, PINOD, "voplk2", 0); |
|
|
goto start; |
}
vop->von_flag |= VON_LOCKED;
return 0;
}
int
vop_unlock(struct vnode *vp)
{
struct vopnode *vop = VTOVON(vp);
if ((vop->von_flag & VON_LOCKED) == 0) {
|
panic("vop_unlock not locked"); |
}
vop->von_flag &= ~VON_LOCKED;
if (vop->von_flag & VON_WANTED) {
|
vop->von_flag &= ~VON_WANTED; |
|
|
wakeup((caddr_t) vop); |
}
return 0;
}
int
vop_islocked(struct vnode *vp)
{
struct vopnode *vop = VTOVON(vp);
if (vop->von_flag & VON_LOCKED)
|
return 1; |
else
|
return 0; |
}
SEE ALSO
vnode(9)
AUTHORS
This manual page was written by Doug Rabson.
MidnightBSD 0.3 July 24, 1996 MidnightBSD 0.3