NetBSD/sys/kern/kern_timeout.c

494 lines
14 KiB
C

/* $NetBSD: kern_timeout.c,v 1.21 2007/02/22 04:38:02 matt Exp $ */
/*-
* Copyright (c) 2003, 2006 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* Copyright (c) 2001 Thomas Nordin <nordin@openbsd.org>
* Copyright (c) 2000-2001 Artur Grabowski <art@openbsd.org>
* 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.
* 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.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_timeout.c,v 1.21 2007/02/22 04:38:02 matt Exp $");
/*
* Adapted from OpenBSD: kern_timeout.c,v 1.15 2002/12/08 04:21:07 art Exp,
* modified to match NetBSD's pre-existing callout API.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/callout.h>
#include <sys/mutex.h>
#ifdef DDB
#include <machine/db_machdep.h>
#include <ddb/db_interface.h>
#include <ddb/db_access.h>
#include <ddb/db_sym.h>
#include <ddb/db_output.h>
#endif
/*
* Timeouts are kept in a hierarchical timing wheel. The c_time is the value
* of the global variable "hardclock_ticks" when the timeout should be called.
* There are four levels with 256 buckets each. See 'Scheme 7' in
* "Hashed and Hierarchical Timing Wheels: Efficient Data Structures for
* Implementing a Timer Facility" by George Varghese and Tony Lauck.
*/
#define BUCKETS 1024
#define WHEELSIZE 256
#define WHEELMASK 255
#define WHEELBITS 8
static struct callout_circq timeout_wheel[BUCKETS]; /* Queues of timeouts */
static struct callout_circq timeout_todo; /* Worklist */
#define MASKWHEEL(wheel, time) (((time) >> ((wheel)*WHEELBITS)) & WHEELMASK)
#define BUCKET(rel, abs) \
(((rel) <= (1 << (2*WHEELBITS))) \
? ((rel) <= (1 << WHEELBITS)) \
? &timeout_wheel[MASKWHEEL(0, (abs))] \
: &timeout_wheel[MASKWHEEL(1, (abs)) + WHEELSIZE] \
: ((rel) <= (1 << (3*WHEELBITS))) \
? &timeout_wheel[MASKWHEEL(2, (abs)) + 2*WHEELSIZE] \
: &timeout_wheel[MASKWHEEL(3, (abs)) + 3*WHEELSIZE])
#define MOVEBUCKET(wheel, time) \
CIRCQ_APPEND(&timeout_todo, \
&timeout_wheel[MASKWHEEL((wheel), (time)) + (wheel)*WHEELSIZE])
/*
* All wheels are locked with the same lock (which must also block out all
* interrupts).
*/
kmutex_t callout_mutex;
/*
* Circular queue definitions.
*/
#define CIRCQ_INIT(list) \
do { \
(list)->cq_next_l = (list); \
(list)->cq_prev_l = (list); \
} while (/*CONSTCOND*/0)
#define CIRCQ_INSERT(elem, list) \
do { \
(elem)->cq_prev_e = (list)->cq_prev_e; \
(elem)->cq_next_l = (list); \
(list)->cq_prev_l->cq_next_l = (elem); \
(list)->cq_prev_l = (elem); \
} while (/*CONSTCOND*/0)
#define CIRCQ_APPEND(fst, snd) \
do { \
if (!CIRCQ_EMPTY(snd)) { \
(fst)->cq_prev_l->cq_next_l = (snd)->cq_next_l; \
(snd)->cq_next_l->cq_prev_l = (fst)->cq_prev_l; \
(snd)->cq_prev_l->cq_next_l = (fst); \
(fst)->cq_prev_l = (snd)->cq_prev_l; \
CIRCQ_INIT(snd); \
} \
} while (/*CONSTCOND*/0)
#define CIRCQ_REMOVE(elem) \
do { \
(elem)->cq_next_l->cq_prev_e = (elem)->cq_prev_e; \
(elem)->cq_prev_l->cq_next_e = (elem)->cq_next_e; \
} while (/*CONSTCOND*/0)
#define CIRCQ_FIRST(list) ((list)->cq_next_e)
#define CIRCQ_NEXT(elem) ((elem)->cq_next_e)
#define CIRCQ_LAST(elem,list) ((elem)->cq_next_l == (list))
#define CIRCQ_EMPTY(list) ((list)->cq_next_l == (list))
/*
* Some of the "math" in here is a bit tricky.
*
* We have to beware of wrapping ints.
* We use the fact that any element added to the queue must be added with a
* positive time. That means that any element `to' on the queue cannot be
* scheduled to timeout further in time than INT_MAX, but c->c_time can
* be positive or negative so comparing it with anything is dangerous.
* The only way we can use the c->c_time value in any predictable way
* is when we calculate how far in the future `to' will timeout -
* "c->c_time - hardclock_ticks". The result will always be positive for
* future timeouts and 0 or negative for due timeouts.
*/
#ifdef CALLOUT_EVENT_COUNTERS
static struct evcnt callout_ev_late;
#endif
/*
* callout_barrier:
*
* If the callout is running on another CPU, busy wait until it
* completes.
*/
static inline void
callout_barrier(struct callout *c)
{
#ifdef MULTIPROCESSOR
struct cpu_info *ci, *ci_cur;
LOCK_ASSERT(mutex_owned(&callout_mutex));
/*
* The callout may have already been dispatched to run on the
* current CPU. It's possible for us to arrive here before it
* actually runs because the SPL is dropped from IPL_SCHED in
* softclock(), and IPL_SOFTCLOCK is low priority. We can't deal
* with that race easily, so for now the caller must deal with
* it.
*/
#if 1
ci_cur = curcpu(); /* XXXgcc get around alpha problem */
while ((ci = c->c_oncpu) != NULL && ci != ci_cur &&
ci->ci_data.cpu_callout == c) {
#else
while ((ci = c->c_oncpu) != NULL && ci != curcpu() &&
ci->ci_data.cpu_callout == c) {
#endif
mutex_spin_exit(&callout_mutex);
while (ci->ci_data.cpu_callout == c)
;
mutex_spin_enter(&callout_mutex);
}
c->c_oncpu = NULL;
#endif
}
/*
* callout_startup:
*
* Initialize the callout facility, called at system startup time.
*/
void
callout_startup(void)
{
int b;
CIRCQ_INIT(&timeout_todo);
for (b = 0; b < BUCKETS; b++)
CIRCQ_INIT(&timeout_wheel[b]);
mutex_init(&callout_mutex, MUTEX_SPIN, IPL_SCHED);
#ifdef CALLOUT_EVENT_COUNTERS
evcnt_attach_dynamic(&callout_ev_late, EVCNT_TYPE_MISC,
NULL, "callout", "late");
#endif
}
/*
* callout_init:
*
* Initialize a callout structure.
*/
void
callout_init(struct callout *c)
{
memset(c, 0, sizeof(*c));
}
/*
* callout_reset:
*
* Reset a callout structure with a new function and argument, and
* schedule it to run.
*/
void
callout_reset(struct callout *c, int to_ticks, void (*func)(void *), void *arg)
{
int old_time;
KASSERT(to_ticks >= 0);
mutex_spin_enter(&callout_mutex);
callout_barrier(c);
/* Initialize the time here, it won't change. */
old_time = c->c_time;
c->c_time = to_ticks + hardclock_ticks;
c->c_flags &= ~(CALLOUT_FIRED|CALLOUT_INVOKING);
c->c_func = func;
c->c_arg = arg;
/*
* If this timeout is already scheduled and now is moved
* earlier, reschedule it now. Otherwise leave it in place
* and let it be rescheduled later.
*/
if (callout_pending(c)) {
if (c->c_time - old_time < 0) {
CIRCQ_REMOVE(&c->c_list);
CIRCQ_INSERT(&c->c_list, &timeout_todo);
}
} else {
c->c_flags |= CALLOUT_PENDING;
CIRCQ_INSERT(&c->c_list, &timeout_todo);
}
mutex_spin_exit(&callout_mutex);
}
/*
* callout_schedule:
*
* Schedule a callout to run. The function and argument must
* already be set in the callout structure.
*/
void
callout_schedule(struct callout *c, int to_ticks)
{
int old_time;
KASSERT(to_ticks >= 0);
mutex_spin_enter(&callout_mutex);
callout_barrier(c);
/* Initialize the time here, it won't change. */
old_time = c->c_time;
c->c_time = to_ticks + hardclock_ticks;
c->c_flags &= ~(CALLOUT_FIRED|CALLOUT_INVOKING);
/*
* If this timeout is already scheduled and now is moved
* earlier, reschedule it now. Otherwise leave it in place
* and let it be rescheduled later.
*/
if (callout_pending(c)) {
if (c->c_time - old_time < 0) {
CIRCQ_REMOVE(&c->c_list);
CIRCQ_INSERT(&c->c_list, &timeout_todo);
}
} else {
c->c_flags |= CALLOUT_PENDING;
CIRCQ_INSERT(&c->c_list, &timeout_todo);
}
mutex_spin_exit(&callout_mutex);
}
/*
* callout_stop:
*
* Cancel a pending callout.
*/
void
callout_stop(struct callout *c)
{
mutex_spin_enter(&callout_mutex);
callout_barrier(c);
if (callout_pending(c))
CIRCQ_REMOVE(&c->c_list);
c->c_flags &= ~(CALLOUT_PENDING|CALLOUT_FIRED);
mutex_spin_exit(&callout_mutex);
}
/*
* This is called from hardclock() once every tick.
* We return !0 if we need to schedule a softclock.
*/
int
callout_hardclock(void)
{
int needsoftclock;
mutex_spin_enter(&callout_mutex);
MOVEBUCKET(0, hardclock_ticks);
if (MASKWHEEL(0, hardclock_ticks) == 0) {
MOVEBUCKET(1, hardclock_ticks);
if (MASKWHEEL(1, hardclock_ticks) == 0) {
MOVEBUCKET(2, hardclock_ticks);
if (MASKWHEEL(2, hardclock_ticks) == 0)
MOVEBUCKET(3, hardclock_ticks);
}
}
needsoftclock = !CIRCQ_EMPTY(&timeout_todo);
mutex_spin_exit(&callout_mutex);
return needsoftclock;
}
/* ARGSUSED */
void
softclock(void *v)
{
#ifdef MULTIPROCESSOR
struct cpu_info *ci = curcpu();
#endif
struct callout *c;
void (*func)(void *);
void *arg;
mutex_spin_enter(&callout_mutex);
while (!CIRCQ_EMPTY(&timeout_todo)) {
c = CIRCQ_FIRST(&timeout_todo);
CIRCQ_REMOVE(&c->c_list);
/* If due run it, otherwise insert it into the right bucket. */
if (c->c_time - hardclock_ticks > 0) {
CIRCQ_INSERT(&c->c_list,
BUCKET((c->c_time - hardclock_ticks), c->c_time));
} else {
#ifdef CALLOUT_EVENT_COUNTERS
if (c->c_time - hardclock_ticks < 0)
callout_ev_late.ev_count++;
#endif
c->c_flags = (c->c_flags & ~CALLOUT_PENDING) |
(CALLOUT_FIRED|CALLOUT_INVOKING);
func = c->c_func;
arg = c->c_arg;
#ifdef MULTIPROCESSOR
c->c_oncpu = ci;
ci->ci_data.cpu_callout = c;
#endif
mutex_spin_exit(&callout_mutex);
(*func)(arg);
mutex_spin_enter(&callout_mutex);
#ifdef MULTIPROCESSOR
ci->ci_data.cpu_callout = NULL;
/*
* we can't touch 'c' here because it might be
* freed already.
*/
#endif
}
}
mutex_spin_exit(&callout_mutex);
}
#ifdef DDB
static void
db_show_callout_bucket(struct callout_circq *bucket)
{
struct callout *c;
db_expr_t offset;
const char *name;
static char question[] = "?";
if (CIRCQ_EMPTY(bucket))
return;
for (c = CIRCQ_FIRST(bucket); /*nothing*/; c = CIRCQ_NEXT(&c->c_list)) {
db_find_sym_and_offset((db_addr_t)(intptr_t)c->c_func, &name,
&offset);
name = name ? name : question;
#ifdef _LP64
#define POINTER_WIDTH "%16lx"
#else
#define POINTER_WIDTH "%8lx"
#endif
db_printf("%9d %2d/%-4d " POINTER_WIDTH " %s\n",
c->c_time - hardclock_ticks,
(int)((bucket - timeout_wheel) / WHEELSIZE),
(int)(bucket - timeout_wheel), (u_long) c->c_arg, name);
if (CIRCQ_LAST(&c->c_list, bucket))
break;
}
}
void
db_show_callout(db_expr_t addr, bool haddr, db_expr_t count, const char *modif)
{
int b;
db_printf("hardclock_ticks now: %d\n", hardclock_ticks);
#ifdef _LP64
db_printf(" ticks wheel arg func\n");
#else
db_printf(" ticks wheel arg func\n");
#endif
/*
* Don't lock the callwheel; all the other CPUs are paused
* anyhow, and we might be called in a circumstance where
* some other CPU was paused while holding the lock.
*/
db_show_callout_bucket(&timeout_todo);
for (b = 0; b < BUCKETS; b++)
db_show_callout_bucket(&timeout_wheel[b]);
}
#endif /* DDB */