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 */
53typedef 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 */
66class Callout
67{
68public:
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
135private:
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 ----------------------------------------------
169inline bool
170Callout::IsPending() const
171{
172	return (m_pending);
173}
174
175//- Callout public methods ----------------------------------------------------
176inline
177Callout::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