workqueue.c
/*
* 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>
*
* Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>.
*/
#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>
#include <linux/hardirq.h>
#include <linux/mempolicy.h>
#include <linux/freezer.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
/*
* The per-CPU workqueue (if single thread, we always use the first
* possible cpu).
*
* The sequence counters are for flush_scheduled_work(). It wants to wait
* 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;
struct task_struct *thread;
int run_depth; /* Detect run_workqueue() recursion depth */
int freezeable; /* Freeze the thread during suspend */
} ____cacheline_aligned;
/*
* The externally visible workqueue abstraction is an array of
* per-CPU workqueues:
*/
struct workqueue_struct {
struct cpu_workqueue_struct *cpu_wq;
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_MUTEX(workqueue_mutex);
static LIST_HEAD(workqueues);
static int singlethread_cpu;
/* 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);
}
/*
* Set the workqueue on which a work item is to be run
* - Must *only* be called if the pending flag is set
*/
static inline void set_wq_data(struct work_struct *work, void *wq)
{
unsigned long new;
BUG_ON(!work_pending(work));
new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
atomic_long_set(&work->data, new);
}
static inline void *get_wq_data(struct work_struct *work)
{
return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
}
static int __run_work(struct cpu_workqueue_struct *cwq, struct work_struct *work)
{
int ret = 0;
unsigned long flags;
spin_lock_irqsave(&cwq->lock, flags);
/*
* We need to re-validate the work info after we've gotten
* the cpu_workqueue lock. We can run the work now iff:
*
* - the wq_data still matches the cpu_workqueue_struct
* - AND the work is still marked pending
* - AND the work is still on a list (which will be this
* workqueue_struct list)
*
* All these conditions are important, because we
* need to protect against the work being run right
* now on another CPU (all but the last one might be
* true if it's currently running and has not been
* released yet, for example).
*/
if (get_wq_data(work) == cwq
&& work_pending(work)
&& !list_empty(&work->entry)) {
work_func_t f = work->func;
list_del_init(&work->entry);
spin_unlock_irqrestore(&cwq->lock, flags);
if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
work_release(work);
f(work);
spin_lock_irqsave(&cwq->lock, flags);
cwq->remove_sequence++;
wake_up(&cwq->work_done);
ret = 1;
}
spin_unlock_irqrestore(&cwq->lock, flags);
return ret;
}
/**
* run_scheduled_work - run scheduled work synchronously
* @work: work to run
*
* This checks if the work was pending, and runs it
* synchronously if so. It returns a boolean to indicate
* whether it had any scheduled work to run or not.
*
* NOTE! This _only_ works for normal work_structs. You
* CANNOT use this for delayed work, because the wq data
* for delayed work will not point properly to the per-
* CPU workqueue struct, but will change!
*/
int fastcall run_scheduled_work(struct work_struct *work)
{
for (;;) {
struct cpu_workqueue_struct *cwq;
if (!work_pending(work))
return 0;
if (list_empty(&work->entry))
return 0;
/* NOTE! This depends intimately on __queue_work! */
cwq = get_wq_data(work);
if (!cwq)
return 0;
if (__run_work(cwq, work))
return 1;
}
}
EXPORT_SYMBOL(run_scheduled_work);
/* 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);
set_wq_data(work, cwq);
list_add_tail(&work->entry, &cwq->worklist);
cwq->insert_sequence++;
wake_up(&cwq->more_work);
spin_unlock_irqrestore(&cwq->lock, flags);
}
/**
* queue_work - queue work on a workqueue
* @wq: workqueue to use
* @work: work to queue
*
* Returns 0 if @work was already on a queue, non-zero otherwise.
*
* 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(WORK_STRUCT_PENDING, work_data_bits(work))) {
if (unlikely(is_single_threaded(wq)))
cpu = singlethread_cpu;
BUG_ON(!list_empty(&work->entry));
__queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
ret = 1;
}
put_cpu();
return ret;
}
EXPORT_SYMBOL_GPL(queue_work);
void delayed_work_timer_fn(unsigned long __data)
{
struct delayed_work *dwork = (struct delayed_work *)__data;
struct workqueue_struct *wq = get_wq_data(&dwork->work);
int cpu = smp_processor_id();
if (unlikely(is_single_threaded(wq)))
cpu = singlethread_cpu;
__queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
}
/**
* queue_delayed_work - queue work on a workqueue after delay
* @wq: workqueue to use
* @dwork: delayable work to queue
* @delay: number of jiffies to wait before queueing
*
* Returns 0 if @work was already on a queue, non-zero otherwise.
*/
int fastcall queue_delayed_work(struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
int ret = 0;
struct timer_list *timer = &dwork->timer;
struct work_struct *work = &dwork->work;
timer_stats_timer_set_start_info(timer);
if (delay == 0)
return queue_work(wq, work);
if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
BUG_ON(timer_pending(timer));
BUG_ON(!list_empty(&work->entry));
/* This stores wq for the moment, for the timer_fn */
set_wq_data(work, wq);
timer->expires = jiffies + delay;
timer->data = (unsigned long)dwork;
timer->function = delayed_work_timer_fn;
add_timer(timer);
ret = 1;
}
return ret;
}
EXPORT_SYMBOL_GPL(queue_delayed_work);
/**
* queue_delayed_work_on - queue work on specific CPU after delay
* @cpu: CPU number to execute work on
* @wq: workqueue to use
* @dwork: work to queue
* @delay: number of jiffies to wait before queueing
*
* Returns 0 if @work was already on a queue, non-zero otherwise.
*/
int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
int ret = 0;
struct timer_list *timer = &dwork->timer;
struct work_struct *work = &dwork->work;
if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
BUG_ON(timer_pending(timer));
BUG_ON(!list_empty(&work->entry));
/* This stores wq for the moment, for the timer_fn */
set_wq_data(work, wq);
timer->expires = jiffies + delay;
timer->data = (unsigned long)dwork;
timer->function = delayed_work_timer_fn;
add_timer_on(timer, cpu);
ret = 1;
}
return ret;
}
EXPORT_SYMBOL_GPL(queue_delayed_work_on);
static 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);
work_func_t f = work->func;
list_del_init(cwq->worklist.next);
spin_unlock_irqrestore(&cwq->lock, flags);
BUG_ON(get_wq_data(work) != cwq);
if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
work_release(work);
f(work);
if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
"%s/0x%08x/%d\n",
current->comm, preempt_count(),
current->pid);
printk(KERN_ERR " last function: ");
print_symbol("%s\n", (unsigned long)f);
debug_show_held_locks(current);
dump_stack();
}
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;
if (!cwq->freezeable)
current->flags |= PF_NOFREEZE;
set_user_nice(current, -5);
/* Block and flush all signals */
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
/*
* We inherited MPOL_INTERLEAVE from the booting kernel.
* Set MPOL_DEFAULT to insure node local allocations.
*/
numa_default_policy();
/* 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()) {
if (cwq->freezeable)
try_to_freeze();
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.
* @wq: workqueue to flush
*
* 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 first cpu's area. */
flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
} else {
int cpu;
mutex_lock(&workqueue_mutex);
for_each_online_cpu(cpu)
flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
mutex_unlock(&workqueue_mutex);
}
}
EXPORT_SYMBOL_GPL(flush_workqueue);
static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
int cpu, int freezeable)
{
struct cpu_workqueue_struct *cwq = per_cpu_ptr(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;
cwq->freezeable = freezeable;
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 freezeable)
{
int cpu, destroy = 0;
struct workqueue_struct *wq;
struct task_struct *p;
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return NULL;
wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
if (!wq->cpu_wq) {
kfree(wq);
return NULL;
}
wq->name = name;
mutex_lock(&workqueue_mutex);
if (singlethread) {
INIT_LIST_HEAD(&wq->list);
p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
if (!p)
destroy = 1;
else
wake_up_process(p);
} else {
list_add(&wq->list, &workqueues);
for_each_online_cpu(cpu) {
p = create_workqueue_thread(wq, cpu, freezeable);
if (p) {
kthread_bind(p, cpu);
wake_up_process(p);
} else
destroy = 1;
}
}
mutex_unlock(&workqueue_mutex);
/*
* Was there any error during startup? If yes then clean up:
*/
if (destroy) {
destroy_workqueue(wq);
wq = NULL;
}
return wq;
}
EXPORT_SYMBOL_GPL(__create_workqueue);
static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq;
unsigned long flags;
struct task_struct *p;
cwq = per_cpu_ptr(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);
}
/**
* destroy_workqueue - safely terminate a workqueue
* @wq: target workqueue
*
* Safely destroy a workqueue. All work currently pending will be done first.
*/
void destroy_workqueue(struct workqueue_struct *wq)
{
int cpu;
flush_workqueue(wq);
/* We don't need the distraction of CPUs appearing and vanishing. */
mutex_lock(&workqueue_mutex);
if (is_single_threaded(wq))
cleanup_workqueue_thread(wq, singlethread_cpu);
else {
for_each_online_cpu(cpu)
cleanup_workqueue_thread(wq, cpu);
list_del(&wq->list);
}
mutex_unlock(&workqueue_mutex);
free_percpu(wq->cpu_wq);
kfree(wq);
}
EXPORT_SYMBOL_GPL(destroy_workqueue);
static struct workqueue_struct *keventd_wq;
/**
* schedule_work - put work task in global workqueue
* @work: job to be done
*
* This puts a job in the kernel-global workqueue.
*/
int fastcall schedule_work(struct work_struct *work)
{
return queue_work(keventd_wq, work);
}
EXPORT_SYMBOL(schedule_work);
/**
* schedule_delayed_work - put work task in global workqueue after delay
* @dwork: job to be done
* @delay: number of jiffies to wait or 0 for immediate execution
*
* After waiting for a given time this puts a job in the kernel-global
* workqueue.
*/
int fastcall schedule_delayed_work(struct delayed_work *dwork,
unsigned long delay)
{
timer_stats_timer_set_start_info(&dwork->timer);
return queue_delayed_work(keventd_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work);
/**
* schedule_delayed_work_on - queue work in global workqueue on CPU after delay
* @cpu: cpu to use
* @dwork: job to be done
* @delay: number of jiffies to wait
*
* After waiting for a given time this puts a job in the kernel-global
* workqueue on the specified CPU.
*/
int schedule_delayed_work_on(int cpu,
struct delayed_work *dwork, unsigned long delay)
{
return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work_on);
/**
* schedule_on_each_cpu - call a function on each online CPU from keventd
* @func: the function to call
*
* Returns zero on success.
* Returns -ve errno on failure.
*
* Appears to be racy against CPU hotplug.
*
* schedule_on_each_cpu() is very slow.
*/
int schedule_on_each_cpu(work_func_t func)
{
int cpu;
struct work_struct *works;
works = alloc_percpu(struct work_struct);
if (!works)
return -ENOMEM;
mutex_lock(&workqueue_mutex);
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
INIT_WORK(work, func);
set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
}
mutex_unlock(&workqueue_mutex);
flush_workqueue(keventd_wq);
free_percpu(works);
return 0;
}
void flush_scheduled_work(void)
{
flush_workqueue(keventd_wq);
}
EXPORT_SYMBOL(flush_scheduled_work);
/**
* cancel_rearming_delayed_workqueue - reliably kill off a delayed work whose handler rearms the delayed work.
* @wq: the controlling workqueue structure
* @dwork: the delayed work struct
*/
void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
struct delayed_work *dwork)
{
while (!cancel_delayed_work(dwork))
flush_workqueue(wq);
}
EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
/**
* cancel_rearming_delayed_work - reliably kill off a delayed keventd work whose handler rearms the delayed work.
* @dwork: the delayed work struct
*/
void cancel_rearming_delayed_work(struct delayed_work *dwork)
{
cancel_rearming_delayed_workqueue(keventd_wq, dwork);
}
EXPORT_SYMBOL(cancel_rearming_delayed_work);
/**
* execute_in_process_context - reliably execute the routine with user context
* @fn: the function to execute
* @ew: guaranteed storage for the execute work structure (must
* be available when the work executes)
*
* Executes the function immediately if process context is available,
* otherwise schedules the function for delayed execution.
*
* Returns: 0 - function was executed
* 1 - function was scheduled for execution
*/
int execute_in_process_context(work_func_t fn, struct execute_work *ew)
{
if (!in_interrupt()) {
fn(&ew->work);
return 0;
}
INIT_WORK(&ew->work, fn);
schedule_work(&ew->work);
return 1;
}
EXPORT_SYMBOL_GPL(execute_in_process_context);
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 = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
if (current == cwq->thread)
ret = 1;
return ret;
}
/* Take the work from this (downed) CPU. */
static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
{
struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
struct list_head list;
struct work_struct *work;
spin_lock_irq(&cwq->lock);
list_replace_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(per_cpu_ptr(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:
mutex_lock(&workqueue_mutex);
/* 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) {
struct cpu_workqueue_struct *cwq;
cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
kthread_bind(cwq->thread, hotcpu);
wake_up_process(cwq->thread);
}
mutex_unlock(&workqueue_mutex);
break;
case CPU_UP_CANCELED:
list_for_each_entry(wq, &workqueues, list) {
if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
continue;
/* Unbind so it can run. */
kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
any_online_cpu(cpu_online_map));
cleanup_workqueue_thread(wq, hotcpu);
}
mutex_unlock(&workqueue_mutex);
break;
case CPU_DOWN_PREPARE:
mutex_lock(&workqueue_mutex);
break;
case CPU_DOWN_FAILED:
mutex_unlock(&workqueue_mutex);
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);
mutex_unlock(&workqueue_mutex);
break;
}
return NOTIFY_OK;
}
void init_workqueues(void)
{
singlethread_cpu = first_cpu(cpu_possible_map);
hotcpu_notifier(workqueue_cpu_callback, 0);
keventd_wq = create_workqueue("events");
BUG_ON(!keventd_wq);
}