kernel event handling functions
, const char
, void *func
struct eventhandler_list *
mechanism provides a way for
kernel subsystems to register interest in kernel events and have their
callback functions invoked when these events occur.
The normal way to use this subsystem is via the macro interface. The macros that
can be used for working with event handlers and callback function lists are:
- This macro declares an event handler named by argument
name with callback functions of type
- This macro registers a callback function
func with event handler
name. When invoked, function
func will be invoked with argument
arg as its first parameter along with any
additional parameters passed in via macro
EVENTHANDLER_INVOKE() (see below).
Callback functions are invoked in order of priority. The relative priority
of each callback among other callbacks associated with an event is given
by argument priority, which is an integer
(highest priority), to
priority). The symbol
EVENTHANDLER_PRI_ANY may be used if the
handler does not have a specific priority associated with it. If
registration is successful,
EVENTHANDLER_REGISTER() returns a
cookie of type eventhandler_tag.
- This macro removes a previously registered callback associated with tag
tag from the event handler named by
- This macro is used to invoke all the callbacks associated with event
handler name. This macro is a variadic
one. Additional arguments to the macro after the
name parameter are passed as the second
and subsequent arguments to each registered callback function.
The macros are implemented using the following functions:
eventhandler_register() function is
used to register a callback with a given event. The arguments expected by
this function are:
- A pointer to an existing event handler list, or
NULL, the event handler list
corresponding to argument name is
- The name of the event handler list.
- A pointer to a callback function. Argument
arg is passed to the callback
function func as its first argument
when it is invoked.
- The relative priority of this callback among all the callbacks
registered for this event. Valid values are those in the range
returns a tag that can later be used with
eventhandler_deregister() to remove the
particular callback function.
removes the callback associated with tag
tag from the event handler list pointed
to by list. This function is safe to call
from inside an event handler callback.
returns a pointer to event handler list structure corresponding to event
removes all deregistered callbacks from the event list
Kernel Event Handlers¶
The following event handlers are present in the kernel:
- Callbacks invoked when the system is being sent to sleep.
- Callbacks invoked when the system is being woken up.
- Callbacks invoked when a new entry is created under
- Callbacks invoked when an address is set up on a network interface.
- Callbacks invoked when an interface is cloned.
- Callbacks invoked when a new network interface appears.
- Callbacks invoked when a network interface is taken down.
- Callbacks invoked when a BPF listener attaches to/detaches from network
- Callbacks invoked after a linker file has been loaded.
- Callbacks invoked after a linker file has been successfully unloaded.
- Callbacks invoked before a linker file is about to be unloaded. These
callbacks may be used to return an error and prevent the unload from
- Callbacks invoked when the power profile of the system changes.
- Callbacks invoked when a process performs an
- Callbacks invoked when a process exits.
- Callbacks invoked when a process forks a child.
- Callbacks invoked at shutdown time, before file systems are
- Callbacks invoked at shutdown time, after all file systems are
- Callbacks invoked just before halting the system.
- Callbacks invoked when virtual memory is low.
- Callbacks invoked when the system watchdog timer is reinitialized.
() return a
cookie of type eventhandler_tag
, which may be
used in a subsequent call to
() function returns
a pointer to an event handler list corresponding to parameter
if no such list was found.
facility first appeared in
This manual page was written by Joseph Koshy