1 /*-
2 * Copyright (c) 2011, 2012, 2013 Spectra Logic Corporation
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions, and the following disclaimer,
10 * without modification.
11 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
12 * substantially similar to the "NO WARRANTY" disclaimer below
13 * ("Disclaimer") and any redistribution must be conditioned upon
14 * including a substantially similar Disclaimer requirement for further
15 * binary redistribution.
16 *
17 * NO WARRANTY
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
26 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
27 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGES.
29 *
30 * Authors: Justin T. Gibbs (Spectra Logic Corporation)
31 *
32 * $FreeBSD$
33 */
34
35 /**
36 * \file callout.h
37 *
38 * \brief Interface for timer based callback services.
39 *
40 * Header requirements:
41 *
42 * #include <sys/time.h>
43 *
44 * #include <list>
45 */
46
47 #ifndef _CALLOUT_H_
48 #define _CALLOUT_H_
49
50 /**
51 * \brief Type of the function callback from a Callout.
52 */
53 typedef void CalloutFunc_t(void *);
54
55 /**
56 * \brief Interface to a schedulable one-shot timer with the granularity
57 * of the system clock (see setitimer(2)).
58 *
59 * Determination of callback expiration is triggered by the SIGALRM
60 * signal. Callout callbacks are always delivered from Zfsd's event
61 * processing loop.
62 *
63 * Periodic actions can be triggered via the Callout mechanisms by
64 * resetting the Callout from within its callback.
65 */
66 class Callout
67 {
68 public:
69
70 /**
71 * Initialize the Callout subsystem.
72 */
73 static void Init();
74
75 /**
76 * Function called (via SIGALRM) when our interval
77 * timer expires.
78 */
79 static void AlarmSignalHandler(int);
80
81 /**
82 * Execute callbacks for all callouts that have the same
83 * expiration time as the first callout in the list.
84 */
85 static void ExpireCallouts();
86
87 /** Constructor. */
88 Callout();
89
90 /**
91 * Returns true if callout has not been stopped,
92 * or deactivated since the last time the callout was
93 * reset.
94 */
95 bool IsActive() const;
96
97 /**
98 * Returns true if callout is still waiting to expire.
99 */
100 bool IsPending() const;
101
102 /**
103 * Disestablish a callout.
104 */
105 bool Stop();
106
107 /**
108 * \brief Establish or change a timeout.
109 *
110 * \param interval Timeval indicating the time which must elapse
111 * before this callout fires.
112 * \param func Pointer to the callback function
113 * \param arg Argument pointer to pass to callback function
114 *
115 * \return Cancellation status.
116 * true: The previous callback was pending and therefore
117 * was cancelled.
118 * false: The callout was not pending at the time of this
119 * reset request.
120 * In all cases, a new callout is established.
121 */
122 bool Reset(const timeval &interval, CalloutFunc_t *func, void *arg);
123
124 /**
125 * \brief Calculate the remaining time until this Callout's timer
126 * expires.
127 *
128 * The return value will be slightly greater than the actual time to
129 * expiry.
130 *
131 * If the callout is not pending, returns INT_MAX.
132 */
133 timeval TimeRemaining() const;
134
135 private:
136 /**
137 * All active callouts sorted by expiration time. The callout
138 * with the nearest expiration time is at the head of the list.
139 */
140 static std::list<Callout *> s_activeCallouts;
141
142 /**
143 * The interval timer has expired. This variable is set from
144 * signal handler context and tested from Zfsd::EventLoop()
145 * context via ExpireCallouts().
146 */
147 static bool s_alarmFired;
148
149 /**
150 * Time, relative to others in the active list, until
151 * this callout is fired.
152 */
153 timeval m_interval;
154
155 /** Callback function argument. */
156 void *m_arg;
157
158 /**
159 * The callback function associated with this timer
160 * entry.
161 */
162 CalloutFunc_t *m_func;
163
164 /** State of this callout. */
165 bool m_pending;
166 };
167
168 //- Callout public const methods ----------------------------------------------
169 inline bool
IsPending()170 Callout::IsPending() const
171 {
172 return (m_pending);
173 }
174
175 //- Callout public methods ----------------------------------------------------
176 inline
Callout()177 Callout::Callout()
178 : m_arg(0),
179 m_func(NULL),
180 m_pending(false)
181 {
182 timerclear(&m_interval);
183 }
184
185 #endif /* CALLOUT_H_ */
186