NAME
knote,
knote_locked —
raise kernel event
SYNOPSIS
#include
<sys/param.h>
#include <sys/event.h>
void
knote(struct
klist *list, long
hint);
void
knote_locked(struct
klist *list, long
hint);
DESCRIPTION
The
knote()
and knote_locked() functions provide 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 locks and 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_locked()
is like knote() but assumes that the
list is already locked.
knote()
and knote_locked() must not be called from interrupt
contexts running at an interrupt priority level higher than
splsched().
SEE ALSO
HISTORY
The knote() functions first appeared in
FreeBSD 4.1, and then in OpenBSD
2.9.
AUTHORS
The kqueue() system was written by
Jonathan Lemon
<jlemon@FreeBSD.org>.