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/*-
* Copyright (c) 2011, 2012, 2013 Spectra Logic Corporation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce at minimum a disclaimer
* substantially similar to the "NO WARRANTY" disclaimer below
* ("Disclaimer") and any redistribution must be conditioned upon
* including a substantially similar Disclaimer requirement for further
* binary redistribution.
*
* NO WARRANTY
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*
* Authors: Justin T. Gibbs (Spectra Logic Corporation)
*/
/**
* \file callout.h
*
* \brief Interface for timer based callback services.
*
* Header requirements:
*
* #include <sys/time.h>
*
* #include <list>
*/
#ifndef _CALLOUT_H_
#define _CALLOUT_H_
/**
* \brief Type of the function callback from a Callout.
*/
typedef void CalloutFunc_t(void *);
/**
* \brief Interface to a schedulable one-shot timer with the granularity
* of the system clock (see setitimer(2)).
*
* Determination of callback expiration is triggered by the SIGALRM
* signal. Callout callbacks are always delivered from Zfsd's event
* processing loop.
*
* Periodic actions can be triggered via the Callout mechanisms by
* resetting the Callout from within its callback.
*/
class Callout
{
public:
/**
* Initialize the Callout subsystem.
*/
static void Init();
/**
* Function called (via SIGALRM) when our interval
* timer expires.
*/
static void AlarmSignalHandler(int);
/**
* Execute callbacks for all callouts that have the same
* expiration time as the first callout in the list.
*/
static void ExpireCallouts();
/** Constructor. */
Callout();
/**
* Returns true if callout has not been stopped,
* or deactivated since the last time the callout was
* reset.
*/
bool IsActive() const;
/**
* Returns true if callout is still waiting to expire.
*/
bool IsPending() const;
/**
* Disestablish a callout.
*/
bool Stop();
/**
* \brief Establish or change a timeout.
*
* \param interval Timeval indicating the time which must elapse
* before this callout fires.
* \param func Pointer to the callback function
* \param arg Argument pointer to pass to callback function
*
* \return Cancellation status.
* true: The previous callback was pending and therefore
* was cancelled.
* false: The callout was not pending at the time of this
* reset request.
* In all cases, a new callout is established.
*/
bool Reset(const timeval &interval, CalloutFunc_t *func, void *arg);
/**
* \brief Calculate the remaining time until this Callout's timer
* expires.
*
* The return value will be slightly greater than the actual time to
* expiry.
*
* If the callout is not pending, returns INT_MAX.
*/
timeval TimeRemaining() const;
private:
/**
* All active callouts sorted by expiration time. The callout
* with the nearest expiration time is at the head of the list.
*/
static std::list<Callout *> s_activeCallouts;
/**
* The interval timer has expired. This variable is set from
* signal handler context and tested from Zfsd::EventLoop()
* context via ExpireCallouts().
*/
static bool s_alarmFired;
/**
* Time, relative to others in the active list, until
* this callout is fired.
*/
timeval m_interval;
/** Callback function argument. */
void *m_arg;
/**
* The callback function associated with this timer
* entry.
*/
CalloutFunc_t *m_func;
/** State of this callout. */
bool m_pending;
};
//- Callout public const methods ----------------------------------------------
inline bool
Callout::IsPending() const
{
return (m_pending);
}
//- Callout public methods ----------------------------------------------------
inline
Callout::Callout()
: m_arg(0),
m_func(NULL),
m_pending(false)
{
timerclear(&m_interval);
}
#endif /* CALLOUT_H_ */
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