KASSERT(9) BSD Kernel Developer's Manual KASSERT(9)NAME
KASSERT -- kernel expression verification macro
SYNOPSIS
options INVARIANTS
#include <sys/param.h>
#include <sys/systm.h>
KASSERT(expression, msg);
DESCRIPTION
In a kernel compiled with options INVARIANTS, the KASSERT() macro tests the given expression and if it is false, calls the panic(9) function,
terminating the running system.
In a kernel that does not have options INVARIANTS, the KASSERT() macro is defined to be a no-op. The second argument is a printf(9) format
string and its arguments, enclosed in parentheses.
EXAMPLES
The kernel function vput() must not be called with a NULL pointer.
void
vput(vp)
struct vnode *vp;
{
struct proc *p = curproc;
KASSERT(vp != NULL, ("vput: null vp"));
...
}
SEE ALSO config(8), panic(9)AUTHORS
This manual page was written by Jonathan M. Bresler <jmb@FreeBSD.org>.
BSD January 14, 2000 BSD
Check Out this Related Man Page
VRELE(9) BSD Kernel Developer's Manual VRELE(9)NAME
vput, vrele, vunref -- decrement the use count for a vnode
SYNOPSIS
#include <sys/param.h>
#include <sys/vnode.h>
void
vput(struct vnode *vp);
void
vrele(struct vnode *vp);
void
vunref(struct vnode *vp);
DESCRIPTION
Decrement the v_usecount field of a vnode.
vp the vnode to decrement
The vrele() function takes an unlocked vnode and returns with the vnode unlocked.
The vput() function should be given a locked vnode as argument, the vnode is unlocked after the function returned. The vput() is opera-
tionally equivalent to calling VOP_UNLOCK(9) followed by vrele(9), with less overhead.
The vunref() function takes a locked vnode as argument, and returns with the vnode locked.
Any code in the system which signified its use of a vnode by usecount should call one of the listed function to decrement use counter. If
the v_usecount field of the non-doomed vnode reaches zero, then it will be inactivated and placed on the free list. Since the functions
might need to call VOPs for the vnode, the Giant mutex should be conditionally locked around the call.
The hold count for the vnode is always greater or equal to the usecount. Non-forced unmount fails when mount point owns a vnode that has
non-zero usecount, see vflush(9).
SEE ALSO vget(9), vnode(9), vref(9), vrefcnt(9)AUTHORS
This manual page was written by Doug Rabson and
Konstantin Belousov.
BSD November 20, 2010 BSD
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