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31 .Nd kernel event handling functions
33 .In sys/eventhandler.h
34 .Fn EVENTHANDLER_DECLARE name type
35 .Fn EVENTHANDLER_DEFINE name func arg priority
36 .Fn EVENTHANDLER_INVOKE name ...
38 .Fn EVENTHANDLER_REGISTER name func arg priority
39 .Fn EVENTHANDLER_DEREGISTER name tag
41 .Fo eventhandler_register
42 .Fa "struct eventhandler_list *list"
43 .Fa "const char *name"
49 .Fo eventhandler_deregister
50 .Fa "struct eventhandler_list *list"
51 .Fa "eventhandler_tag tag"
53 .Ft "struct eventhandler_list *"
54 .Fn eventhandler_find_list "const char *name"
56 .Fn eventhandler_prune_list "struct eventhandler_list *list"
60 mechanism provides a way for kernel subsystems to register interest in
61 kernel events and have their callback functions invoked when these
64 Callback functions are invoked in order of priority.
65 The relative priority of each callback among other callbacks
66 associated with an event is given by argument
68 which is an integer ranging from
69 .Dv EVENTHANDLER_PRI_FIRST
70 (highest priority), to
71 .Dv EVENTHANDLER_PRI_LAST
74 .Dv EVENTHANDLER_PRI_ANY
75 may be used if the handler does not have a specific priority
78 The normal way to use this subsystem is via the macro interface.
79 The macros that can be used for working with event handlers and callback
81 .Bl -tag -width indent
82 .It Fn EVENTHANDLER_DECLARE
83 This macro declares an event handler named by argument
85 with callback functions of type
87 .It Fn EVENTHANDLER_DEFINE
90 to register a callback function
94 When invoked, function
96 will be invoked with argument
98 as its first parameter along with any additional parameters passed in
100 .Fn EVENTHANDLER_INVOKE
102 .It Fn EVENTHANDLER_REGISTER
103 This macro registers a callback function
107 When invoked, function
109 will be invoked with argument
111 as its first parameter along with any additional parameters passed in
113 .Fn EVENTHANDLER_INVOKE
115 If registration is successful,
116 .Fn EVENTHANDLER_REGISTER
117 returns a cookie of type
118 .Vt eventhandler_tag .
119 .It Fn EVENTHANDLER_DEREGISTER
120 This macro removes a previously registered callback associated with tag
122 from the event handler named by argument
124 .It Fn EVENTHANDLER_INVOKE
125 This macro is used to invoke all the callbacks associated with event
128 This macro is a variadic one.
129 Additional arguments to the macro after the
131 parameter are passed as the second and subsequent arguments to each
132 registered callback function.
135 The macros are implemented using the following functions:
136 .Bl -tag -width indent
137 .It Fn eventhandler_register
139 .Fn eventhandler_register
140 function is used to register a callback with a given event.
141 The arguments expected by this function are:
142 .Bl -tag -width ".Fa priority"
144 A pointer to an existing event handler list, or
150 the event handler list corresponding to argument
154 The name of the event handler list.
156 A pointer to a callback function.
159 is passed to the callback function
161 as its first argument when it is invoked.
163 The relative priority of this callback among all the callbacks
164 registered for this event.
165 Valid values are those in the range
166 .Dv EVENTHANDLER_PRI_FIRST
168 .Dv EVENTHANDLER_PRI_LAST .
172 .Fn eventhandler_register
175 that can later be used with
176 .Fn eventhandler_deregister
177 to remove the particular callback function.
178 .It Fn eventhandler_deregister
180 .Fn eventhandler_deregister
181 function removes the callback associated with tag
183 from the event handler list pointed to by
185 This function is safe to call from inside an event handler
187 .It Fn eventhandler_find_list
189 .Fn eventhandler_find_list
190 function returns a pointer to event handler list structure corresponding
193 .It Fn eventhandler_prune_list
195 .Fn eventhandler_prune_list
196 function removes all deregistered callbacks from the event list
199 .Ss Kernel Event Handlers
200 The following event handlers are present in the kernel:
201 .Bl -tag -width indent
202 .It Vt acpi_sleep_event
203 Callbacks invoked when the system is being sent to sleep.
204 .It Vt acpi_wakeup_event
205 Callbacks invoked when the system is being woken up.
206 .It Vt app_coredump_start
207 Callbacks invoked at start of application core dump.
208 .It Vt app_coredump_progress
209 Callbacks invoked during progress of application core dump.
210 .It Vt app_coredump_finish
211 Callbacks invoked at finish of application core dump.
212 .It Vt app_coredump_error
213 Callbacks invoked on error of application core dump.
215 Callbacks invoked when a BPF listener attaches to/detaches from network interface.
216 .It Vt cpufreq_levels_changed
217 Callback invoked when cpu frequency levels have changed.
218 .It Vt cpufreq_post_change
219 Callback invoked after cpu frequency has changed.
220 .It Vt cpufreq_pre_change
221 Callback invoked before cpu frequency has changed.
223 Callback invoked to poll for dcons changes.
225 Callbacks invoked when a new entry is created under
227 .It Vt group_attach_event
228 Callback invoked when an interfance has been added to an interface group.
229 .It Vt group_change_event
230 Callback invoked when an change has been made to an interface group.
231 .It Vt group_detach_event
232 Callback invoked when an interfance has been removed from an interface group.
234 Callbacks invoked when an address is set up on a network interface.
235 .It Vt if_clone_event
236 Callbacks invoked when an interface is cloned.
237 .It Vt iflladdr_event
238 Callback invoked when an if link layer address event has happened.
239 .It Vt ifnet_arrival_event
240 Callbacks invoked when a new network interface appears.
241 .It Vt ifnet_departure_event
242 Callbacks invoked when a network interface is taken down.
243 .It Vt ifnet_link_event
244 Callback invoked when an interfance link event has happened.
246 Callbacks invoked after a linker file has been loaded.
248 Callbacks invoked after a linker file has been successfully unloaded.
249 .It Vt kld_unload_try
250 Callbacks invoked before a linker file is about to be unloaded.
251 These callbacks may be used to return an error and prevent the unload from
254 Callback invoked when an link layer event has happened.
255 .It Vt nmbclusters_change
256 Callback invoked when the number of mbuf clusters has changed.
258 Callback invoked when the number of mbufs has changed.
259 .It Vt maxsockets_change
260 Callback invoked when the maximum number of sockets has changed.
262 Callback invoked when root has been mounted.
263 .It Vt power_profile_change
264 Callbacks invoked when the power profile of the system changes.
266 Callback invoked when the system has resumed.
268 Callback invoked just before the system is suspended.
270 Callback invoked when a process is created.
272 Callback invoked when a process is destroyed.
274 Callbacks invoked when a process performs an
278 Callbacks invoked when a process exits.
280 Callback invoked when a process memory is destroyed.
281 This is never called.
283 Callbacks invoked when a process forks a child.
285 Callback invoked when a process is initalized.
286 .It Vt random_adaptor_attach
287 Callback invoked when a new random module has been loaded.
288 .It Vt register_framebuffer
289 Callback invoked when a new frame buffer is registered.
290 .It Vt route_redirect_event
291 Callback invoked when a route gets redirected to a new location.
292 .It Vt shutdown_pre_sync
293 Callbacks invoked at shutdown time, before file systems are synchronized.
294 .It Vt shutdown_post_sync
295 Callbacks invoked at shutdown time, after all file systems are synchronized.
296 .It Vt shutdown_final
297 Callbacks invoked just before halting the system.
298 .It Vt tcp_offload_listen_start
299 Callback invoked for TCP Offload to start listening for new connections.
300 .It Vt tcp_offload_listen_stop
301 Callback invoked ror TCP Offload to stop listening for new connections.
303 Callback invoked when a thread object is created.
305 Callback invoked when a thread object is destroyed.
307 Callback invoked when a thread object is initalized.
309 Callback invoked when a thread object is deinitalized.
310 .It Vt usb_dev_configured
311 Callback invoked when a USB device is configured
312 .It Vt unregister_framebuffer
313 Callback invoked when a frame buffer is deregistered.
315 Callback invoked when a file system is mounted.
317 Callback invoked when a file system is unmounted.
319 Callback invoked when the vlan configuration has changed.
321 Callback invoked when a vlan is destroyed.
323 Callbacks invoked when virtual memory is low.
325 Callbacks invoked when the system watchdog timer is reinitialized.
329 .Fn EVENTHANDLER_REGISTER
331 .Fn eventhandler_register
332 return a cookie of type
333 .Vt eventhandler_tag ,
334 which may be used in a subsequent call to
335 .Fn EVENTHANDLER_DEREGISTER
337 .Fn eventhandler_deregister .
340 .Fn eventhandler_find_list
342 returns a pointer to an event handler list corresponding to parameter
346 if no such list was found.
350 facility first appeared in
353 This manual page was written by
354 .An Joseph Koshy Aq Mt jkoshy@FreeBSD.org .