1 .\" $NetBSD: timeout.9,v 1.2 1996/06/23 22:32:34 pk Exp $
3 .\" Copyright (c) 1996 The NetBSD Foundation, Inc.
4 .\" All rights reserved.
6 .\" This code is derived from software contributed to The NetBSD Foundation
7 .\" by Paul Kranenburg.
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19 .\" This product includes software developed by the NetBSD
20 .\" Foundation, Inc. and its contributors.
21 .\" 4. Neither the name of The NetBSD Foundation nor the names of its
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25 .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
26 .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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37 .\" $FreeBSD: src/share/man/man9/timeout.9,v 1.9.2.6 2001/12/17 11:30:19 ru Exp $
39 .Dd September 10, 1996
44 .Nd execute a function after a specified length of time
50 typedef void timeout_t (void *);
52 .Ft struct callout_handle
53 .Fn timeout "timeout_t *func" "void *arg" "int ticks"
55 .Fn callout_handle_init "struct callout_handle *handle"
58 struct callout_handle handle = CALLOUT_HANDLE_INITIALIZER(&handle)
61 .Fn untimeout "timeout_t *func" "void *arg" "struct callout_handle handle"
63 .Fn callout_init "struct callout *c"
65 .Fn callout_stop "struct callout *c"
67 .Fn callout_reset "struct callout *c" "int ticks" "timeout_t *func" "void *arg"
71 schedules a call to the function given by the argument
76 Non-positive values of
78 are silently converted to the value
81 should be a pointer to a function that takes a
92 .Ft struct callout_handle
93 which can be used in conjunction with the
95 function to request that a scheduled timeout be canceled.
98 .Fn callout_handle_init
99 can be used to initialize a handle to a state which will cause
100 any calls to untimeout with that handle to return with no side
103 Assigning a callout handle the value of
104 .Fn CALLOUT_HANDLE_INITIALIZER
105 performs the same function as
106 .Fn callout_handle_init
107 and is provided for use on statically declared or global callout handles.
111 cancels the timeout associated with
117 arguments to validate the handle.
118 If the handle does not correspond to a timeout with
125 must be initialized by a previous call to
127 .Fn callout_handle_init ,
128 or assigned the value of
129 .Fn CALLOUT_HANDLE_INITIALIZER "&handle"
130 before being passed to
132 The behavior of calling untimeout without a previously initialized handle
135 As handles are recycled by the system, it is possible (although unlikely)
136 that a handle from one invocation of
138 may match the handle of another invocation of
140 if both calls used the same function pointer and argument, and the first
141 timeout is expired or canceled before the second call.
142 The timeout facility offers O(1) running time for
146 Timeouts are executed from
150 Thus they are protected from re-entrancy.
157 are low-level routines for clients who wish to allocate their own
162 initializes a callout so it can be passed to
166 without any side effects.
170 cancels a callout if it is currently pending.
171 If the callout is pending, then
173 will return a non-zero value.
174 If the callout has already been serviced or is currently being serviced,
175 then zero will be returned.
181 to disestablish the callout, and then establishes a new callout in the
188 .Ft struct callout_handle
189 that can be passed to
193 function returns non-zero if the callout is still pending or zero otherwise.
195 The current timeout and untimeout routines are based on the work of
198 .An George Varghese ,
199 published in a technical report entitled
200 .%T "Redesigning the BSD Callout and Timer Facilities"
201 and modified slightly for inclusion in
204 .An Justin T. Gibbs .
205 The original work on the data structures used in this implementation
211 .%T "Hashed and Hierarchical Timing Wheels: Data Structures for the Efficient Implementation of a Timer Facility"
213 .%B "Proceedings of the 11th ACM Annual Symposium on Operating Systems Principles" .
214 The current implementation replaces the long standing
217 callout mechanism which offered O(n) insertion and removal running time
218 but did not generate or require handles for untimeout operations.