KNOTE(9) FreeBSD Kernel Developer's Manual KNOTE(9)
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
kqueue(2)
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 <
[email protected]>.
FreeBSD 14.1-RELEASE-p8 February 10, 2023 FreeBSD 14.1-RELEASE-p8