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workqueue: misc/cosmetic updates

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Make the following updates in preparation of concurrency managed
workqueue.  None of these changes causes any visible behavior
difference.

* Add comments and adjust indentations to data structures and several
  functions.

* Rename wq_per_cpu() to get_cwq() and swap the position of two
  parameters for consistency.  Convert a direct per_cpu_ptr() access
  to wq->cpu_wq to get_cwq().

* Add work_static() and Update set_wq_data() such that it sets the
  flags part to WORK_STRUCT_PENDING | WORK_STRUCT_STATIC if static |
  @extra_flags.

* Move santiy check on work->entry emptiness from queue_work_on() to
  __queue_work() which all queueing paths share.

* Make __queue_work() take @cpu and @wq instead of @cwq.

* Restructure flush_work() and __create_workqueue_key() to make them
  easier to modify.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2010-06-29 10:07:10 +02:00
parent c790bce048
commit 4690c4ab56
2 changed files with 89 additions and 47 deletions
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5
include/linux/workqueue.h
View File

@ -96,9 +96,14 @@ struct execute_work {
#ifdef CONFIG_DEBUG_OBJECTS_WORK
extern void __init_work(struct work_struct *work, int onstack);
extern void destroy_work_on_stack(struct work_struct *work);
static inline unsigned int work_static(struct work_struct *work)
{
return *work_data_bits(work) & (1 << WORK_STRUCT_STATIC);
}
#else
static inline void __init_work(struct work_struct *work, int onstack) { }
static inline void destroy_work_on_stack(struct work_struct *work) { }
static inline unsigned int work_static(struct work_struct *work) { return 0; }
#endif
/*

127
kernel/workqueue.c
View File

@ -36,6 +36,16 @@
#define CREATE_TRACE_POINTS
#include <trace/events/workqueue.h>
/*
* Structure fields follow one of the following exclusion rules.
*
* I: Set during initialization and read-only afterwards.
*
* L: cwq->lock protected. Access with cwq->lock held.
*
* W: workqueue_lock protected.
*/
/*
* The per-CPU workqueue (if single thread, we always use the first
* possible cpu).
@ -48,7 +58,7 @@ struct cpu_workqueue_struct {
wait_queue_head_t more_work;
struct work_struct *current_work;
struct workqueue_struct *wq;
struct workqueue_struct *wq; /* I: the owning workqueue */
struct task_struct *thread;
} ____cacheline_aligned;
@ -57,9 +67,9 @@ struct cpu_workqueue_struct {
* per-CPU workqueues:
*/
struct workqueue_struct {
struct cpu_workqueue_struct *cpu_wq;
struct list_head list;
const char *name;
struct cpu_workqueue_struct *cpu_wq; /* I: cwq's */
struct list_head list; /* W: list of all workqueues */
const char *name; /* I: workqueue name */
int singlethread;
int freezeable; /* Freeze threads during suspend */
#ifdef CONFIG_LOCKDEP
@ -204,8 +214,8 @@ static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)
? cpu_singlethread_map : cpu_populated_map;
}
static
struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
struct workqueue_struct *wq)
{
if (unlikely(is_wq_single_threaded(wq)))
cpu = singlethread_cpu;
@ -217,15 +227,13 @@ struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
* - Must *only* be called if the pending flag is set
*/
static inline void set_wq_data(struct work_struct *work,
struct cpu_workqueue_struct *cwq)
struct cpu_workqueue_struct *cwq,
unsigned long extra_flags)
{
unsigned long new;
BUG_ON(!work_pending(work));
new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
atomic_long_set(&work->data, new);
atomic_long_set(&work->data, (unsigned long)cwq | work_static(work) |
(1UL << WORK_STRUCT_PENDING) | extra_flags);
}
/*
@ -233,9 +241,7 @@ static inline void set_wq_data(struct work_struct *work,
*/
static inline void clear_wq_data(struct work_struct *work)
{
unsigned long flags = *work_data_bits(work) &
(1UL << WORK_STRUCT_STATIC);
atomic_long_set(&work->data, flags);
atomic_long_set(&work->data, work_static(work));
}
static inline
@ -244,29 +250,47 @@ struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
}
/**
* insert_work - insert a work into cwq
* @cwq: cwq @work belongs to
* @work: work to insert
* @head: insertion point
* @extra_flags: extra WORK_STRUCT_* flags to set
*
* Insert @work into @cwq after @head.
*
* CONTEXT:
* spin_lock_irq(cwq->lock).
*/
static void insert_work(struct cpu_workqueue_struct *cwq,
struct work_struct *work, struct list_head *head)
struct work_struct *work, struct list_head *head,
unsigned int extra_flags)
{
trace_workqueue_insertion(cwq->thread, work);
set_wq_data(work, cwq);
/* we own @work, set data and link */
set_wq_data(work, cwq, extra_flags);
/*
* Ensure that we get the right work->data if we see the
* result of list_add() below, see try_to_grab_pending().
*/
smp_wmb();
list_add_tail(&work->entry, head);
wake_up(&cwq->more_work);
}
static void __queue_work(struct cpu_workqueue_struct *cwq,
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
unsigned long flags;
debug_work_activate(work);
spin_lock_irqsave(&cwq->lock, flags);
insert_work(cwq, work, &cwq->worklist);
BUG_ON(!list_empty(&work->entry));
insert_work(cwq, work, &cwq->worklist, 0);
spin_unlock_irqrestore(&cwq->lock, flags);
}
@ -308,8 +332,7 @@ queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
int ret = 0;
if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
BUG_ON(!list_empty(&work->entry));
__queue_work(wq_per_cpu(wq, cpu), work);
__queue_work(cpu, wq, work);
ret = 1;
}
return ret;
@ -320,9 +343,8 @@ static void delayed_work_timer_fn(unsigned long __data)
{
struct delayed_work *dwork = (struct delayed_work *)__data;
struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
struct workqueue_struct *wq = cwq->wq;
__queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
__queue_work(smp_processor_id(), cwq->wq, &dwork->work);
}
/**
@ -366,7 +388,7 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
timer_stats_timer_set_start_info(&dwork->timer);
/* This stores cwq for the moment, for the timer_fn */
set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
set_wq_data(work, get_cwq(raw_smp_processor_id(), wq), 0);
timer->expires = jiffies + delay;
timer->data = (unsigned long)dwork;
timer->function = delayed_work_timer_fn;
@ -430,6 +452,12 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
spin_unlock_irq(&cwq->lock);
}
/**
* worker_thread - the worker thread function
* @__cwq: cwq to serve
*
* The cwq worker thread function.
*/
static int worker_thread(void *__cwq)
{
struct cpu_workqueue_struct *cwq = __cwq;
@ -468,6 +496,17 @@ static void wq_barrier_func(struct work_struct *work)
complete(&barr->done);
}
/**
* insert_wq_barrier - insert a barrier work
* @cwq: cwq to insert barrier into
* @barr: wq_barrier to insert
* @head: insertion point
*
* Insert barrier @barr into @cwq before @head.
*
* CONTEXT:
* spin_lock_irq(cwq->lock).
*/
static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
struct wq_barrier *barr, struct list_head *head)
{
@ -479,11 +518,10 @@ static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
*/
INIT_WORK_ON_STACK(&barr->work, wq_barrier_func);
__set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
init_completion(&barr->done);
debug_work_activate(&barr->work);
insert_work(cwq, &barr->work, head);
insert_work(cwq, &barr->work, head, 0);
}
static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
@ -517,9 +555,6 @@ static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
*
* 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 flush_workqueue(struct workqueue_struct *wq)
{
@ -558,7 +593,6 @@ int flush_work(struct work_struct *work)
lock_map_acquire(&cwq->wq->lockdep_map);
lock_map_release(&cwq->wq->lockdep_map);
prev = NULL;
spin_lock_irq(&cwq->lock);
if (!list_empty(&work->entry)) {
/*
@ -567,22 +601,22 @@ int flush_work(struct work_struct *work)
*/
smp_rmb();
if (unlikely(cwq != get_wq_data(work)))
goto out;
goto already_gone;
prev = &work->entry;
} else {
if (cwq->current_work != work)
goto out;
goto already_gone;
prev = &cwq->worklist;
}
insert_wq_barrier(cwq, &barr, prev->next);
out:
spin_unlock_irq(&cwq->lock);
if (!prev)
return 0;
spin_unlock_irq(&cwq->lock);
wait_for_completion(&barr.done);
destroy_work_on_stack(&barr.work);
return 1;
already_gone:
spin_unlock_irq(&cwq->lock);
return 0;
}
EXPORT_SYMBOL_GPL(flush_work);
@ -665,7 +699,7 @@ static void wait_on_work(struct work_struct *work)
cpu_map = wq_cpu_map(wq);
for_each_cpu(cpu, cpu_map)
wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
wait_on_cpu_work(get_cwq(cpu, wq), work);
}
static int __cancel_work_timer(struct work_struct *work,
@ -782,9 +816,8 @@ EXPORT_SYMBOL(schedule_delayed_work);
void flush_delayed_work(struct delayed_work *dwork)
{
if (del_timer_sync(&dwork->timer)) {
struct cpu_workqueue_struct *cwq;
cwq = wq_per_cpu(get_wq_data(&dwork->work)->wq, get_cpu());
__queue_work(cwq, &dwork->work);
__queue_work(get_cpu(), get_wq_data(&dwork->work)->wq,
&dwork->work);
put_cpu();
}
flush_work(&dwork->work);
@ -991,13 +1024,11 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return NULL;
goto err;
wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
if (!wq->cpu_wq) {
kfree(wq);
return NULL;
}
if (!wq->cpu_wq)
goto err;
wq->name = name;
lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
@ -1041,6 +1072,12 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
wq = NULL;
}
return wq;
err:
if (wq) {
free_percpu(wq->cpu_wq);
kfree(wq);
}
return NULL;
}
EXPORT_SYMBOL_GPL(__create_workqueue_key);