freebsd-dev/sys/kern/subr_taskqueue.c
John Baldwin 0f180a7cce Change msleep() and tsleep() to not alter the calling thread's priority
if the specified priority is zero.  This avoids a race where the calling
thread could read a snapshot of it's current priority, then a different
thread could change the first thread's priority, then the original thread
would call sched_prio() inside msleep() undoing the change made by the
second thread.  I used a priority of zero as no thread that calls msleep()
or tsleep() should be specifying a priority of zero anyway.

The various places that passed 'curthread->td_priority' or some variant
as the priority now pass 0.
2006-04-17 18:20:38 +00:00

432 lines
10 KiB
C

/*-
* Copyright (c) 2000 Doug Rabson
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/taskqueue.h>
#include <sys/unistd.h>
#include <machine/stdarg.h>
static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
static void *taskqueue_giant_ih;
static void *taskqueue_ih;
static STAILQ_HEAD(taskqueue_list, taskqueue) taskqueue_queues;
static struct mtx taskqueue_queues_mutex;
struct taskqueue {
STAILQ_ENTRY(taskqueue) tq_link;
STAILQ_HEAD(, task) tq_queue;
const char *tq_name;
taskqueue_enqueue_fn tq_enqueue;
void *tq_context;
struct task *tq_running;
struct mtx tq_mutex;
struct proc **tq_pproc;
int tq_pcount;
int tq_spin;
int tq_flags;
};
#define TQ_FLAGS_ACTIVE (1 << 0)
static __inline void
TQ_LOCK(struct taskqueue *tq)
{
if (tq->tq_spin)
mtx_lock_spin(&tq->tq_mutex);
else
mtx_lock(&tq->tq_mutex);
}
static __inline void
TQ_UNLOCK(struct taskqueue *tq)
{
if (tq->tq_spin)
mtx_unlock_spin(&tq->tq_mutex);
else
mtx_unlock(&tq->tq_mutex);
}
static void init_taskqueue_list(void *data);
static __inline int
TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
int t)
{
if (tq->tq_spin)
return (msleep_spin(p, m, wm, t));
return (msleep(p, m, pri, wm, t));
}
static void
init_taskqueue_list(void *data __unused)
{
mtx_init(&taskqueue_queues_mutex, "taskqueue list", NULL, MTX_DEF);
STAILQ_INIT(&taskqueue_queues);
}
SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
NULL);
static struct taskqueue *
_taskqueue_create(const char *name, int mflags,
taskqueue_enqueue_fn enqueue, void *context,
int mtxflags, const char *mtxname)
{
struct taskqueue *queue;
queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
if (!queue)
return 0;
STAILQ_INIT(&queue->tq_queue);
queue->tq_name = name;
queue->tq_enqueue = enqueue;
queue->tq_context = context;
queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
queue->tq_flags |= TQ_FLAGS_ACTIVE;
mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
mtx_lock(&taskqueue_queues_mutex);
STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
mtx_unlock(&taskqueue_queues_mutex);
return queue;
}
struct taskqueue *
taskqueue_create(const char *name, int mflags,
taskqueue_enqueue_fn enqueue, void *context)
{
return _taskqueue_create(name, mflags, enqueue, context,
MTX_DEF, "taskqueue");
}
/*
* Signal a taskqueue thread to terminate.
*/
static void
taskqueue_terminate(struct proc **pp, struct taskqueue *tq)
{
while (tq->tq_pcount > 0) {
wakeup(tq);
TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
}
}
void
taskqueue_free(struct taskqueue *queue)
{
mtx_lock(&taskqueue_queues_mutex);
STAILQ_REMOVE(&taskqueue_queues, queue, taskqueue, tq_link);
mtx_unlock(&taskqueue_queues_mutex);
TQ_LOCK(queue);
queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
taskqueue_run(queue);
taskqueue_terminate(queue->tq_pproc, queue);
mtx_destroy(&queue->tq_mutex);
free(queue->tq_pproc, M_TASKQUEUE);
free(queue, M_TASKQUEUE);
}
/*
* Returns with the taskqueue locked.
*/
struct taskqueue *
taskqueue_find(const char *name)
{
struct taskqueue *queue;
mtx_lock(&taskqueue_queues_mutex);
STAILQ_FOREACH(queue, &taskqueue_queues, tq_link) {
if (strcmp(queue->tq_name, name) == 0) {
TQ_LOCK(queue);
mtx_unlock(&taskqueue_queues_mutex);
return queue;
}
}
mtx_unlock(&taskqueue_queues_mutex);
return NULL;
}
int
taskqueue_enqueue(struct taskqueue *queue, struct task *task)
{
struct task *ins;
struct task *prev;
TQ_LOCK(queue);
/*
* Count multiple enqueues.
*/
if (task->ta_pending) {
task->ta_pending++;
TQ_UNLOCK(queue);
return 0;
}
/*
* Optimise the case when all tasks have the same priority.
*/
prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
if (!prev || prev->ta_priority >= task->ta_priority) {
STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
} else {
prev = 0;
for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
prev = ins, ins = STAILQ_NEXT(ins, ta_link))
if (ins->ta_priority < task->ta_priority)
break;
if (prev)
STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
else
STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
}
task->ta_pending = 1;
queue->tq_enqueue(queue->tq_context);
TQ_UNLOCK(queue);
return 0;
}
void
taskqueue_run(struct taskqueue *queue)
{
struct task *task;
int owned, pending;
owned = mtx_owned(&queue->tq_mutex);
if (!owned)
TQ_LOCK(queue);
while (STAILQ_FIRST(&queue->tq_queue)) {
/*
* Carefully remove the first task from the queue and
* zero its pending count.
*/
task = STAILQ_FIRST(&queue->tq_queue);
STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
pending = task->ta_pending;
task->ta_pending = 0;
queue->tq_running = task;
TQ_UNLOCK(queue);
task->ta_func(task->ta_context, pending);
TQ_LOCK(queue);
queue->tq_running = NULL;
wakeup(task);
}
/*
* For compatibility, unlock on return if the queue was not locked
* on entry, although this opens a race window.
*/
if (!owned)
TQ_UNLOCK(queue);
}
void
taskqueue_drain(struct taskqueue *queue, struct task *task)
{
if (queue->tq_spin) { /* XXX */
mtx_lock_spin(&queue->tq_mutex);
while (task->ta_pending != 0 || task == queue->tq_running)
msleep_spin(task, &queue->tq_mutex, "-", 0);
mtx_unlock_spin(&queue->tq_mutex);
} else {
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
mtx_lock(&queue->tq_mutex);
while (task->ta_pending != 0 || task == queue->tq_running)
msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
mtx_unlock(&queue->tq_mutex);
}
}
static void
taskqueue_swi_enqueue(void *context)
{
swi_sched(taskqueue_ih, 0);
}
static void
taskqueue_swi_run(void *dummy)
{
taskqueue_run(taskqueue_swi);
}
static void
taskqueue_swi_giant_enqueue(void *context)
{
swi_sched(taskqueue_giant_ih, 0);
}
static void
taskqueue_swi_giant_run(void *dummy)
{
taskqueue_run(taskqueue_swi_giant);
}
int
taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
const char *name, ...)
{
va_list ap;
struct taskqueue *tq;
char ktname[MAXCOMLEN];
int i, error;
if (count <= 0)
return (EINVAL);
tq = *tqp;
va_start(ap, name);
vsnprintf(ktname, MAXCOMLEN, name, ap);
va_end(ap);
tq->tq_pproc = malloc(sizeof(struct proc *) * count, M_TASKQUEUE,
M_NOWAIT | M_ZERO);
if (tq->tq_pproc == NULL) {
printf("%s: no memory for %s threads\n", __func__, ktname);
return (ENOMEM);
}
for (i = 0; i < count; i++) {
if (count == 1)
error = kthread_create(taskqueue_thread_loop, tqp,
&tq->tq_pproc[i], 0, 0, ktname);
else
error = kthread_create(taskqueue_thread_loop, tqp,
&tq->tq_pproc[i], 0, 0, "%s_%d", ktname, i);
if (error == 0) {
mtx_lock_spin(&sched_lock);
sched_prio(FIRST_THREAD_IN_PROC(tq->tq_pproc[i]), pri);
mtx_unlock_spin(&sched_lock);
tq->tq_pcount++;
} else {
/* should be ok to continue, taskqueue_free will dtrt */
printf("%s: kthread_create(%s): error %d",
__func__, ktname, error);
}
}
return (0);
}
void
taskqueue_thread_loop(void *arg)
{
struct taskqueue **tqp, *tq;
tqp = arg;
tq = *tqp;
TQ_LOCK(tq);
do {
taskqueue_run(tq);
TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
} while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0);
/* rendezvous with thread that asked us to terminate */
tq->tq_pcount--;
wakeup_one(tq->tq_pproc);
TQ_UNLOCK(tq);
kthread_exit(0);
}
void
taskqueue_thread_enqueue(void *context)
{
struct taskqueue **tqp, *tq;
tqp = context;
tq = *tqp;
mtx_assert(&tq->tq_mutex, MA_OWNED);
wakeup_one(tq);
}
TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
INTR_MPSAFE, &taskqueue_ih));
TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, 0,
swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
TASKQUEUE_DEFINE_THREAD(thread);
struct taskqueue *
taskqueue_create_fast(const char *name, int mflags,
taskqueue_enqueue_fn enqueue, void *context)
{
return _taskqueue_create(name, mflags, enqueue, context,
MTX_SPIN, "fast_taskqueue");
}
/* NB: for backwards compatibility */
int
taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
{
return taskqueue_enqueue(queue, task);
}
static void *taskqueue_fast_ih;
static void
taskqueue_fast_enqueue(void *context)
{
swi_sched(taskqueue_fast_ih, 0);
}
static void
taskqueue_fast_run(void *dummy)
{
taskqueue_run(taskqueue_fast);
}
TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, 0,
swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));