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/*
* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stddef.h>
#include <latch.h>
#include <gpxe/list.h>
#include <gpxe/process.h>
#include <gpxe/init.h>
#include <gpxe/retry.h>
/** @file
*
* Retry timers
*
* A retry timer is a truncated binary exponential backoff timer. It
* can be used to build automatic retransmission into network
* protocols.
*/
/** List of running timers */
static LIST_HEAD ( timers );
/**
* Reload timer
*
* @v timer Retry timer
*
* This reloads the timer with a new expiry time. The expiry time
* will be the timer's base timeout value, shifted left by the number
* of retries (i.e. the number of timer expiries since the last timer
* reset).
*/
static void reload_timer ( struct retry_timer *timer ) {
unsigned int exp;
exp = timer->retries;
if ( exp > BACKOFF_LIMIT )
exp = BACKOFF_LIMIT;
timer->expiry = currticks() + ( timer->base << exp );
}
/**
* Reset timer
*
* @v timer Retry timer
*
* This resets the timer, i.e. clears its retry count and starts it
* running with its base timeout value.
*
* Note that it is explicitly permitted to call reset_timer() on an
* inactive timer.
*/
void reset_timer ( struct retry_timer *timer ) {
timer->retries = 0;
reload_timer ( timer );
}
/**
* Start timer
*
* @v timer Retry timer
*
* This resets the timer and starts it running (i.e. adds it to the
* list of running timers). The retry_timer::base and
* retry_timer::callback fields must have been filled in.
*/
void start_timer ( struct retry_timer *timer ) {
list_add ( &timer->list, &timers );
reset_timer ( timer );
}
/**
* Stop timer
*
* @v timer Retry timer
*
* This stops the timer (i.e. removes it from the list of running
* timers).
*/
void stop_timer ( struct retry_timer *timer ) {
list_del ( &timer->list );
}
/**
* Single-step the retry timer list
*
* @v process Retry timer process
*/
static void retry_step ( struct process *process ) {
struct retry_timer *timer;
struct retry_timer *tmp;
unsigned long now = currticks();
list_for_each_entry_safe ( timer, tmp, &timers, list ) {
if ( timer->expiry <= now ) {
timer->retries++;
reload_timer ( timer );
timer->expired ( timer );
}
}
schedule ( process );
}
/** Retry timer process */
static struct process retry_process = {
.step = retry_step,
};
/** Initialise the retry timer module */
static void init_retry ( void ) {
schedule ( &retry_process );
}
INIT_FN ( INIT_PROCESS, init_retry, NULL, NULL );
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