FreeBSD-5.3/sys/kern/kern_timeout.c
/*-
* Copyright (c) 1982, 1986, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, 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 DAMAGE.
*
* From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/kern/kern_timeout.c,v 1.91 2004/08/06 21:49:00 rwatson Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/condvar.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
static int avg_depth;
SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
"Average number of items examined per softclock call. Units = 1/1000");
static int avg_gcalls;
SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
"Average number of Giant callouts made per softclock call. Units = 1/1000");
static int avg_mpcalls;
SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
"Average number of MP callouts made per softclock call. Units = 1/1000");
/*
* TODO:
* allocate more timeout table slots when table overflows.
*/
/* Exported to machdep.c and/or kern_clock.c. */
struct callout *callout;
struct callout_list callfree;
int callwheelsize, callwheelbits, callwheelmask;
struct callout_tailq *callwheel;
int softticks; /* Like ticks, but for softclock(). */
struct mtx callout_lock;
#ifdef DIAGNOSTIC
struct mtx dont_sleep_in_callout;
#endif
static struct callout *nextsoftcheck; /* Next callout to be checked. */
/*-
* Locked by callout_lock:
* curr_callout - If a callout is in progress, it is curr_callout.
* If curr_callout is non-NULL, threads waiting on
* callout_wait will be woken up as soon as the
* relevant callout completes.
* wakeup_ctr - Incremented every time a thread wants to wait
* for a callout to complete. Modified only when
* curr_callout is non-NULL.
* wakeup_needed - If a thread is waiting on callout_wait, then
* wakeup_needed is nonzero. Increased only when
* cutt_callout is non-NULL.
*/
static struct callout *curr_callout;
static int wakeup_ctr;
static int wakeup_needed;
/*-
* Locked by callout_wait_lock:
* callout_wait - If wakeup_needed is set, callout_wait will be
* triggered after the current callout finishes.
* wakeup_done_ctr - Set to the current value of wakeup_ctr after
* callout_wait is triggered.
*/
static struct mtx callout_wait_lock;
static struct cv callout_wait;
static int wakeup_done_ctr;
/*
* kern_timeout_callwheel_alloc() - kernel low level callwheel initialization
*
* This code is called very early in the kernel initialization sequence,
* and may be called more then once.
*/
caddr_t
kern_timeout_callwheel_alloc(caddr_t v)
{
/*
* Calculate callout wheel size
*/
for (callwheelsize = 1, callwheelbits = 0;
callwheelsize < ncallout;
callwheelsize <<= 1, ++callwheelbits)
;
callwheelmask = callwheelsize - 1;
callout = (struct callout *)v;
v = (caddr_t)(callout + ncallout);
callwheel = (struct callout_tailq *)v;
v = (caddr_t)(callwheel + callwheelsize);
return(v);
}
/*
* kern_timeout_callwheel_init() - initialize previously reserved callwheel
* space.
*
* This code is called just once, after the space reserved for the
* callout wheel has been finalized.
*/
void
kern_timeout_callwheel_init(void)
{
int i;
SLIST_INIT(&callfree);
for (i = 0; i < ncallout; i++) {
callout_init(&callout[i], 0);
callout[i].c_flags = CALLOUT_LOCAL_ALLOC;
SLIST_INSERT_HEAD(&callfree, &callout[i], c_links.sle);
}
for (i = 0; i < callwheelsize; i++) {
TAILQ_INIT(&callwheel[i]);
}
mtx_init(&callout_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
#ifdef DIAGNOSTIC
mtx_init(&dont_sleep_in_callout, "dont_sleep_in_callout", NULL, MTX_DEF);
#endif
mtx_init(&callout_wait_lock, "callout_wait_lock", NULL, MTX_DEF);
cv_init(&callout_wait, "callout_wait");
}
/*
* The callout mechanism is based on the work of Adam M. Costello and
* George Varghese, published in a technical report entitled "Redesigning
* the BSD Callout and Timer Facilities" and modified slightly for inclusion
* in FreeBSD by Justin T. Gibbs. The original work on the data structures
* used in this implementation was published by G. Varghese and T. Lauck in
* the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
* the Efficient Implementation of a Timer Facility" in the Proceedings of
* the 11th ACM Annual Symposium on Operating Systems Principles,
* Austin, Texas Nov 1987.
*/
/*
* Software (low priority) clock interrupt.
* Run periodic events from timeout queue.
*/
void
softclock(void *dummy)
{
struct callout *c;
struct callout_tailq *bucket;
int curticks;
int steps; /* #steps since we last allowed interrupts */
int depth;
int mpcalls;
int gcalls;
int wakeup_cookie;
#ifdef DIAGNOSTIC
struct bintime bt1, bt2;
struct timespec ts2;
static uint64_t maxdt = 36893488147419102LL; /* 2 msec */
static timeout_t *lastfunc;
#endif
#ifndef MAX_SOFTCLOCK_STEPS
#define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
#endif /* MAX_SOFTCLOCK_STEPS */
mpcalls = 0;
gcalls = 0;
depth = 0;
steps = 0;
mtx_lock_spin(&callout_lock);
while (softticks != ticks) {
softticks++;
/*
* softticks may be modified by hard clock, so cache
* it while we work on a given bucket.
*/
curticks = softticks;
bucket = &callwheel[curticks & callwheelmask];
c = TAILQ_FIRST(bucket);
while (c) {
depth++;
if (c->c_time != curticks) {
c = TAILQ_NEXT(c, c_links.tqe);
++steps;
if (steps >= MAX_SOFTCLOCK_STEPS) {
nextsoftcheck = c;
/* Give interrupts a chance. */
mtx_unlock_spin(&callout_lock);
; /* nothing */
mtx_lock_spin(&callout_lock);
c = nextsoftcheck;
steps = 0;
}
} else {
void (*c_func)(void *);
void *c_arg;
int c_flags;
nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
TAILQ_REMOVE(bucket, c, c_links.tqe);
c_func = c->c_func;
c_arg = c->c_arg;
c_flags = c->c_flags;
c->c_func = NULL;
if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
c->c_flags = CALLOUT_LOCAL_ALLOC;
SLIST_INSERT_HEAD(&callfree, c,
c_links.sle);
} else {
c->c_flags =
(c->c_flags & ~CALLOUT_PENDING);
}
curr_callout = c;
mtx_unlock_spin(&callout_lock);
if (!(c_flags & CALLOUT_MPSAFE)) {
mtx_lock(&Giant);
gcalls++;
CTR1(KTR_CALLOUT, "callout %p", c_func);
} else {
mpcalls++;
CTR1(KTR_CALLOUT, "callout mpsafe %p",
c_func);
}
#ifdef DIAGNOSTIC
binuptime(&bt1);
mtx_lock(&dont_sleep_in_callout);
#endif
c_func(c_arg);
#ifdef DIAGNOSTIC
mtx_unlock(&dont_sleep_in_callout);
binuptime(&bt2);
bintime_sub(&bt2, &bt1);
if (bt2.frac > maxdt) {
if (lastfunc != c_func ||
bt2.frac > maxdt * 2) {
bintime2timespec(&bt2, &ts2);
printf(
"Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
c_func, c_arg,
(intmax_t)ts2.tv_sec,
ts2.tv_nsec);
}
maxdt = bt2.frac;
lastfunc = c_func;
}
#endif
if (!(c_flags & CALLOUT_MPSAFE))
mtx_unlock(&Giant);
mtx_lock_spin(&callout_lock);
curr_callout = NULL;
if (wakeup_needed) {
/*
* There might be someone waiting
* for the callout to complete.
*/
wakeup_cookie = wakeup_ctr;
mtx_unlock_spin(&callout_lock);
mtx_lock(&callout_wait_lock);
cv_broadcast(&callout_wait);
wakeup_done_ctr = wakeup_cookie;
mtx_unlock(&callout_wait_lock);
mtx_lock_spin(&callout_lock);
wakeup_needed = 0;
}
steps = 0;
c = nextsoftcheck;
}
}
}
avg_depth += (depth * 1000 - avg_depth) >> 8;
avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
nextsoftcheck = NULL;
mtx_unlock_spin(&callout_lock);
}
/*
* timeout --
* Execute a function after a specified length of time.
*
* untimeout --
* Cancel previous timeout function call.
*
* callout_handle_init --
* Initialize a handle so that using it with untimeout is benign.
*
* See AT&T BCI Driver Reference Manual for specification. This
* implementation differs from that one in that although an
* identification value is returned from timeout, the original
* arguments to timeout as well as the identifier are used to
* identify entries for untimeout.
*/
struct callout_handle
timeout(ftn, arg, to_ticks)
timeout_t *ftn;
void *arg;
int to_ticks;
{
struct callout *new;
struct callout_handle handle;
mtx_lock_spin(&callout_lock);
/* Fill in the next free callout structure. */
new = SLIST_FIRST(&callfree);
if (new == NULL)
/* XXX Attempt to malloc first */
panic("timeout table full");
SLIST_REMOVE_HEAD(&callfree, c_links.sle);
callout_reset(new, to_ticks, ftn, arg);
handle.callout = new;
mtx_unlock_spin(&callout_lock);
return (handle);
}
void
untimeout(ftn, arg, handle)
timeout_t *ftn;
void *arg;
struct callout_handle handle;
{
/*
* Check for a handle that was initialized
* by callout_handle_init, but never used
* for a real timeout.
*/
if (handle.callout == NULL)
return;
mtx_lock_spin(&callout_lock);
if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
callout_stop(handle.callout);
mtx_unlock_spin(&callout_lock);
}
void
callout_handle_init(struct callout_handle *handle)
{
handle->callout = NULL;
}
/*
* New interface; clients allocate their own callout structures.
*
* callout_reset() - establish or change a timeout
* callout_stop() - disestablish a timeout
* callout_init() - initialize a callout structure so that it can
* safely be passed to callout_reset() and callout_stop()
*
* <sys/callout.h> defines three convenience macros:
*
* callout_active() - returns truth if callout has not been serviced
* callout_pending() - returns truth if callout is still waiting for timeout
* callout_deactivate() - marks the callout as having been serviced
*/
void
callout_reset(c, to_ticks, ftn, arg)
struct callout *c;
int to_ticks;
void (*ftn)(void *);
void *arg;
{
mtx_lock_spin(&callout_lock);
if (c == curr_callout && wakeup_needed) {
/*
* We're being asked to reschedule a callout which is
* currently in progress, and someone has called
* callout_drain to kill that callout. Don't reschedule.
*/
mtx_unlock_spin(&callout_lock);
return;
}
if (c->c_flags & CALLOUT_PENDING) {
if (nextsoftcheck == c) {
nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
}
TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c,
c_links.tqe);
/*
* Part of the normal "stop a pending callout" process
* is to clear the CALLOUT_ACTIVE and CALLOUT_PENDING
* flags. We're not going to bother doing that here,
* because we're going to be setting those flags ten lines
* after this point, and we're holding callout_lock
* between now and then.
*/
}
/*
* We could unlock callout_lock here and lock it again before the
* TAILQ_INSERT_TAIL, but there's no point since doing this setup
* doesn't take much time.
*/
if (to_ticks <= 0)
to_ticks = 1;
c->c_arg = arg;
c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
c->c_func = ftn;
c->c_time = ticks + to_ticks;
TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask],
c, c_links.tqe);
mtx_unlock_spin(&callout_lock);
}
int
_callout_stop_safe(c, safe)
struct callout *c;
int safe;
{
int wakeup_cookie;
mtx_lock_spin(&callout_lock);
/*
* Don't attempt to delete a callout that's not on the queue.
*/
if (!(c->c_flags & CALLOUT_PENDING)) {
c->c_flags &= ~CALLOUT_ACTIVE;
if (c == curr_callout && safe) {
/* We need to wait until the callout is finished. */
wakeup_needed = 1;
wakeup_cookie = wakeup_ctr++;
mtx_unlock_spin(&callout_lock);
mtx_lock(&callout_wait_lock);
/*
* Check to make sure that softclock() didn't
* do the wakeup in between our dropping
* callout_lock and picking up callout_wait_lock
*/
if (wakeup_cookie - wakeup_done_ctr > 0)
cv_wait(&callout_wait, &callout_wait_lock);
mtx_unlock(&callout_wait_lock);
} else
mtx_unlock_spin(&callout_lock);
return (0);
}
c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
if (nextsoftcheck == c) {
nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
}
TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe);
c->c_func = NULL;
if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
}
mtx_unlock_spin(&callout_lock);
return (1);
}
void
callout_init(c, mpsafe)
struct callout *c;
int mpsafe;
{
bzero(c, sizeof *c);
if (mpsafe)
c->c_flags |= CALLOUT_MPSAFE;
}
#ifdef APM_FIXUP_CALLTODO
/*
* Adjust the kernel calltodo timeout list. This routine is used after
* an APM resume to recalculate the calltodo timer list values with the
* number of hz's we have been sleeping. The next hardclock() will detect
* that there are fired timers and run softclock() to execute them.
*
* Please note, I have not done an exhaustive analysis of what code this
* might break. I am motivated to have my select()'s and alarm()'s that
* have expired during suspend firing upon resume so that the applications
* which set the timer can do the maintanence the timer was for as close
* as possible to the originally intended time. Testing this code for a
* week showed that resuming from a suspend resulted in 22 to 25 timers
* firing, which seemed independant on whether the suspend was 2 hours or
* 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
*/
void
adjust_timeout_calltodo(time_change)
struct timeval *time_change;
{
register struct callout *p;
unsigned long delta_ticks;
/*
* How many ticks were we asleep?
* (stolen from tvtohz()).
*/
/* Don't do anything */
if (time_change->tv_sec < 0)
return;
else if (time_change->tv_sec <= LONG_MAX / 1000000)
delta_ticks = (time_change->tv_sec * 1000000 +
time_change->tv_usec + (tick - 1)) / tick + 1;
else if (time_change->tv_sec <= LONG_MAX / hz)
delta_ticks = time_change->tv_sec * hz +
(time_change->tv_usec + (tick - 1)) / tick + 1;
else
delta_ticks = LONG_MAX;
if (delta_ticks > INT_MAX)
delta_ticks = INT_MAX;
/*
* Now rip through the timer calltodo list looking for timers
* to expire.
*/
/* don't collide with softclock() */
mtx_lock_spin(&callout_lock);
for (p = calltodo.c_next; p != NULL; p = p->c_next) {
p->c_time -= delta_ticks;
/* Break if the timer had more time on it than delta_ticks */
if (p->c_time > 0)
break;
/* take back the ticks the timer didn't use (p->c_time <= 0) */
delta_ticks = -p->c_time;
}
mtx_unlock_spin(&callout_lock);
return;
}
#endif /* APM_FIXUP_CALLTODO */