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Commit 4690c4ab authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: misc/cosmetic updates 



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: default avatarTejun Heo <tj@kernel.org>
parent c790bce0

include/linux/workqueue.h

+5 −0
Original line number Diff line number Diff line
@@ -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



/*

kernel/workqueue.c

+84 −47
Original line number Diff line number Diff line
@@ -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);