blob: 5301935f609b7ea38f94b25d1c5863a92c354561 [file] [log] [blame]
/*
* linux/kernel/workqueue.c
*
* Generic mechanism for defining kernel helper threads for running
* arbitrary tasks in process context.
*
* Started by Ingo Molnar, Copyright (C) 2002
*
* Derived from the taskqueue/keventd code by:
*
* David Woodhouse <dwmw2@infradead.org>
* Andrew Morton <andrewm@uow.edu.au>
* Kai Petzke <wpp@marie.physik.tu-berlin.de>
* Theodore Ts'o <tytso@mit.edu>
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/completion.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
/*
* The per-CPU workqueue (if single thread, we always use cpu 0's).
*
* The sequence counters are for flush_scheduled_work(). It wants to wait
* until until all currently-scheduled works are completed, but it doesn't
* want to be livelocked by new, incoming ones. So it waits until
* remove_sequence is >= the insert_sequence which pertained when
* flush_scheduled_work() was called.
*/
struct cpu_workqueue_struct {
spinlock_t lock;
long remove_sequence; /* Least-recently added (next to run) */
long insert_sequence; /* Next to add */
struct list_head worklist;
wait_queue_head_t more_work;
wait_queue_head_t work_done;
struct workqueue_struct *wq;
task_t *thread;
int run_depth; /* Detect run_workqueue() recursion depth */
} ____cacheline_aligned;
/*
* The externally visible workqueue abstraction is an array of
* per-CPU workqueues:
*/
struct workqueue_struct {
struct cpu_workqueue_struct cpu_wq[NR_CPUS];
const char *name;
struct list_head list; /* Empty if single thread */
};
/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
threads to each one as cpus come/go. */
static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues);
/* If it's single threaded, it isn't in the list of workqueues. */
static inline int is_single_threaded(struct workqueue_struct *wq)
{
return list_empty(&wq->list);
}
/* Preempt must be disabled. */
static void __queue_work(struct cpu_workqueue_struct *cwq,
struct work_struct *work)
{
unsigned long flags;
spin_lock_irqsave(&cwq->lock, flags);
work->wq_data = cwq;
list_add_tail(&work->entry, &cwq->worklist);
cwq->insert_sequence++;
wake_up(&cwq->more_work);
spin_unlock_irqrestore(&cwq->lock, flags);
}
/*
* Queue work on a workqueue. Return non-zero if it was successfully
* added.
*
* We queue the work to the CPU it was submitted, but there is no
* guarantee that it will be processed by that CPU.
*/
int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
{
int ret = 0, cpu = get_cpu();
if (!test_and_set_bit(0, &work->pending)) {
if (unlikely(is_single_threaded(wq)))
cpu = 0;
BUG_ON(!list_empty(&work->entry));
__queue_work(wq->cpu_wq + cpu, work);
ret = 1;
}
put_cpu();
return ret;
}
static void delayed_work_timer_fn(unsigned long __data)
{
struct work_struct *work = (struct work_struct *)__data;
struct workqueue_struct *wq = work->wq_data;
int cpu = smp_processor_id();
if (unlikely(is_single_threaded(wq)))
cpu = 0;
__queue_work(wq->cpu_wq + cpu, work);
}
int fastcall queue_delayed_work(struct workqueue_struct *wq,
struct work_struct *work, unsigned long delay)
{
int ret = 0;
struct timer_list *timer = &work->timer;
if (!test_and_set_bit(0, &work->pending)) {
BUG_ON(timer_pending(timer));
BUG_ON(!list_empty(&work->entry));
/* This stores wq for the moment, for the timer_fn */
work->wq_data = wq;
timer->expires = jiffies + delay;
timer->data = (unsigned long)work;
timer->function = delayed_work_timer_fn;
add_timer(timer);
ret = 1;
}
return ret;
}
static inline void run_workqueue(struct cpu_workqueue_struct *cwq)
{
unsigned long flags;
/*
* Keep taking off work from the queue until
* done.
*/
spin_lock_irqsave(&cwq->lock, flags);
cwq->run_depth++;
if (cwq->run_depth > 3) {
/* morton gets to eat his hat */
printk("%s: recursion depth exceeded: %d\n",
__FUNCTION__, cwq->run_depth);
dump_stack();
}
while (!list_empty(&cwq->worklist)) {
struct work_struct *work = list_entry(cwq->worklist.next,
struct work_struct, entry);
void (*f) (void *) = work->func;
void *data = work->data;
list_del_init(cwq->worklist.next);
spin_unlock_irqrestore(&cwq->lock, flags);
BUG_ON(work->wq_data != cwq);
clear_bit(0, &work->pending);
f(data);
spin_lock_irqsave(&cwq->lock, flags);
cwq->remove_sequence++;
wake_up(&cwq->work_done);
}
cwq->run_depth--;
spin_unlock_irqrestore(&cwq->lock, flags);
}
static int worker_thread(void *__cwq)
{
struct cpu_workqueue_struct *cwq = __cwq;
DECLARE_WAITQUEUE(wait, current);
struct k_sigaction sa;
sigset_t blocked;
current->flags |= PF_NOFREEZE;
set_user_nice(current, -5);
/* Block and flush all signals */
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
/* SIG_IGN makes children autoreap: see do_notify_parent(). */
sa.sa.sa_handler = SIG_IGN;
sa.sa.sa_flags = 0;
siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
add_wait_queue(&cwq->more_work, &wait);
if (list_empty(&cwq->worklist))
schedule();
else
__set_current_state(TASK_RUNNING);
remove_wait_queue(&cwq->more_work, &wait);
if (!list_empty(&cwq->worklist))
run_workqueue(cwq);
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}
static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
{
if (cwq->thread == current) {
/*
* Probably keventd trying to flush its own queue. So simply run
* it by hand rather than deadlocking.
*/
run_workqueue(cwq);
} else {
DEFINE_WAIT(wait);
long sequence_needed;
spin_lock_irq(&cwq->lock);
sequence_needed = cwq->insert_sequence;
while (sequence_needed - cwq->remove_sequence > 0) {
prepare_to_wait(&cwq->work_done, &wait,
TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&cwq->lock);
schedule();
spin_lock_irq(&cwq->lock);
}
finish_wait(&cwq->work_done, &wait);
spin_unlock_irq(&cwq->lock);
}
}
/*
* flush_workqueue - ensure that any scheduled work has run to completion.
*
* Forces execution of the workqueue and blocks until its completion.
* This is typically used in driver shutdown handlers.
*
* This function will sample each workqueue's current insert_sequence number and
* will sleep until the head sequence is greater than or equal to that. This
* means that we sleep until all works which were queued on entry have been
* handled, but we are not livelocked by new incoming ones.
*
* This function used to run the workqueues itself. Now we just wait for the
* helper threads to do it.
*/
void fastcall flush_workqueue(struct workqueue_struct *wq)
{
might_sleep();
if (is_single_threaded(wq)) {
/* Always use cpu 0's area. */
flush_cpu_workqueue(wq->cpu_wq + 0);
} else {
int cpu;
lock_cpu_hotplug();
for_each_online_cpu(cpu)
flush_cpu_workqueue(wq->cpu_wq + cpu);
unlock_cpu_hotplug();
}
}
static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
int cpu)
{
struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
struct task_struct *p;
spin_lock_init(&cwq->lock);
cwq->wq = wq;
cwq->thread = NULL;
cwq->insert_sequence = 0;
cwq->remove_sequence = 0;
INIT_LIST_HEAD(&cwq->worklist);
init_waitqueue_head(&cwq->more_work);
init_waitqueue_head(&cwq->work_done);
if (is_single_threaded(wq))
p = kthread_create(worker_thread, cwq, "%s", wq->name);
else
p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
if (IS_ERR(p))
return NULL;
cwq->thread = p;
return p;
}
struct workqueue_struct *__create_workqueue(const char *name,
int singlethread)
{
int cpu, destroy = 0;
struct workqueue_struct *wq;
struct task_struct *p;
BUG_ON(strlen(name) > 10);
wq = kmalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return NULL;
memset(wq, 0, sizeof(*wq));
wq->name = name;
/* We don't need the distraction of CPUs appearing and vanishing. */
lock_cpu_hotplug();
if (singlethread) {
INIT_LIST_HEAD(&wq->list);
p = create_workqueue_thread(wq, 0);
if (!p)
destroy = 1;
else
wake_up_process(p);
} else {
spin_lock(&workqueue_lock);
list_add(&wq->list, &workqueues);
spin_unlock(&workqueue_lock);
for_each_online_cpu(cpu) {
p = create_workqueue_thread(wq, cpu);
if (p) {
kthread_bind(p, cpu);
wake_up_process(p);
} else
destroy = 1;
}
}
unlock_cpu_hotplug();
/*
* Was there any error during startup? If yes then clean up:
*/
if (destroy) {
destroy_workqueue(wq);
wq = NULL;
}
return wq;
}
static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq;
unsigned long flags;
struct task_struct *p;
cwq = wq->cpu_wq + cpu;
spin_lock_irqsave(&cwq->lock, flags);
p = cwq->thread;
cwq->thread = NULL;
spin_unlock_irqrestore(&cwq->lock, flags);
if (p)
kthread_stop(p);
}
void destroy_workqueue(struct workqueue_struct *wq)
{
int cpu;
flush_workqueue(wq);
/* We don't need the distraction of CPUs appearing and vanishing. */
lock_cpu_hotplug();
if (is_single_threaded(wq))
cleanup_workqueue_thread(wq, 0);
else {
for_each_online_cpu(cpu)
cleanup_workqueue_thread(wq, cpu);
spin_lock(&workqueue_lock);
list_del(&wq->list);
spin_unlock(&workqueue_lock);
}
unlock_cpu_hotplug();
kfree(wq);
}
static struct workqueue_struct *keventd_wq;
int fastcall schedule_work(struct work_struct *work)
{
return queue_work(keventd_wq, work);
}
int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
{
return queue_delayed_work(keventd_wq, work, delay);
}
int schedule_delayed_work_on(int cpu,
struct work_struct *work, unsigned long delay)
{
int ret = 0;
struct timer_list *timer = &work->timer;
if (!test_and_set_bit(0, &work->pending)) {
BUG_ON(timer_pending(timer));
BUG_ON(!list_empty(&work->entry));
/* This stores keventd_wq for the moment, for the timer_fn */
work->wq_data = keventd_wq;
timer->expires = jiffies + delay;
timer->data = (unsigned long)work;
timer->function = delayed_work_timer_fn;
add_timer_on(timer, cpu);
ret = 1;
}
return ret;
}
void flush_scheduled_work(void)
{
flush_workqueue(keventd_wq);
}
int keventd_up(void)
{
return keventd_wq != NULL;
}
int current_is_keventd(void)
{
struct cpu_workqueue_struct *cwq;
int cpu = smp_processor_id(); /* preempt-safe: keventd is per-cpu */
int ret = 0;
BUG_ON(!keventd_wq);
cwq = keventd_wq->cpu_wq + cpu;
if (current == cwq->thread)
ret = 1;
return ret;
}
#ifdef CONFIG_HOTPLUG_CPU
/* Take the work from this (downed) CPU. */
static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
{
struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
LIST_HEAD(list);
struct work_struct *work;
spin_lock_irq(&cwq->lock);
list_splice_init(&cwq->worklist, &list);
while (!list_empty(&list)) {
printk("Taking work for %s\n", wq->name);
work = list_entry(list.next,struct work_struct,entry);
list_del(&work->entry);
__queue_work(wq->cpu_wq + smp_processor_id(), work);
}
spin_unlock_irq(&cwq->lock);
}
/* We're holding the cpucontrol mutex here */
static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int hotcpu = (unsigned long)hcpu;
struct workqueue_struct *wq;
switch (action) {
case CPU_UP_PREPARE:
/* Create a new workqueue thread for it. */
list_for_each_entry(wq, &workqueues, list) {
if (create_workqueue_thread(wq, hotcpu) < 0) {
printk("workqueue for %i failed\n", hotcpu);
return NOTIFY_BAD;
}
}
break;
case CPU_ONLINE:
/* Kick off worker threads. */
list_for_each_entry(wq, &workqueues, list) {
kthread_bind(wq->cpu_wq[hotcpu].thread, hotcpu);
wake_up_process(wq->cpu_wq[hotcpu].thread);
}
break;
case CPU_UP_CANCELED:
list_for_each_entry(wq, &workqueues, list) {
/* Unbind so it can run. */
kthread_bind(wq->cpu_wq[hotcpu].thread,
smp_processor_id());
cleanup_workqueue_thread(wq, hotcpu);
}
break;
case CPU_DEAD:
list_for_each_entry(wq, &workqueues, list)
cleanup_workqueue_thread(wq, hotcpu);
list_for_each_entry(wq, &workqueues, list)
take_over_work(wq, hotcpu);
break;
}
return NOTIFY_OK;
}
#endif
void init_workqueues(void)
{
hotcpu_notifier(workqueue_cpu_callback, 0);
keventd_wq = create_workqueue("events");
BUG_ON(!keventd_wq);
}
EXPORT_SYMBOL_GPL(__create_workqueue);
EXPORT_SYMBOL_GPL(queue_work);
EXPORT_SYMBOL_GPL(queue_delayed_work);
EXPORT_SYMBOL_GPL(flush_workqueue);
EXPORT_SYMBOL_GPL(destroy_workqueue);
EXPORT_SYMBOL(schedule_work);
EXPORT_SYMBOL(schedule_delayed_work);
EXPORT_SYMBOL(schedule_delayed_work_on);
EXPORT_SYMBOL(flush_scheduled_work);