NAME
knote,
KNOTE —
raise
kernel event
SYNOPSIS
#include <sys/event.h>
void
knote(
struct
klist *list,
long
hint);
KNOTE(
struct
klist *list,
long
hint);
DESCRIPTION
The
knote() function provides a hook into the kqueue kernel
event notification mechanism to allow sections of the kernel to raise a kernel
event in the form of a ‘knote’, which is a
struct
knote as defined in
<sys/event.h>.
knote() takes a singly linked
list of
knotes, along with a
hint (which is passed to the
appropriate filter routine).
knote() then walks the
list making calls to the filter routine for each knote.
As each knote contains a reference to the data structure that it is attached
to, the filter may choose to examine the data structure in deciding whether an
event should be reported. The
hint is used to pass in
additional information, which may not be present in the data structure that
the filter examines.
If the filter decides that the event should be returned, it returns a non-zero
value and
knote() links the knote onto the tail end of the
active list in the corresponding kqueue for the application to retrieve. If
the knote is already on the active list, no action is taken, but the call to
the filter occurs in order to provide an opportunity for the filter to record
the activity.
knote() must not be called from interrupt contexts running at
an interrupt priority level higher than
splsched(9).
KNOTE() is a macro that calls
knote(
list,
hint) if
list is not empty.
SEE ALSO
kqueue(2),
kfilter_register(9)
HISTORY
The
knote() and
KNOTE() functions first
appeared in
FreeBSD 4.1, and then in
NetBSD 2.0.
AUTHORS
The
kqueue(2) system was written
by
Jonathan Lemon
<
jlemon@FreeBSD.org>.