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Commit c34056a3 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: introduce worker 



Separate out worker thread related information to struct worker from
struct cpu_workqueue_struct and implement helper functions to deal
with the new struct worker.  The only change which is visible outside
is that now workqueue worker are all named "kworker/CPUID:WORKERID"
where WORKERID is allocated from per-cpu ida.

This is in preparation of concurrency managed workqueue where shared
multiple workers would be available per cpu.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 73f53c4a

kernel/workqueue.c

+150 −61
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 
#include <linux/kallsyms.h>

#include <linux/debug_locks.h>

#include <linux/lockdep.h>

#include <linux/idr.h>



/*

 * Structure fields follow one of the following exclusion rules.
@@ -46,6 +47,15 @@ 
 * W: workqueue_lock protected.

 */



struct cpu_workqueue_struct;



struct worker {

	struct work_struct	*current_work;	/* L: work being processed */

	struct task_struct	*task;		/* I: worker task */

	struct cpu_workqueue_struct *cwq;	/* I: the associated cwq */

	int			id;		/* I: worker id */

};



/*

 * The per-CPU workqueue (if single thread, we always use the first

 * possible cpu).  The lower WORK_STRUCT_FLAG_BITS of
@@ -58,15 +68,14 @@ struct cpu_workqueue_struct { 


	struct list_head worklist;

	wait_queue_head_t more_work;

	struct work_struct *current_work;

	unsigned int		cpu;

	struct worker		*worker;



	struct workqueue_struct *wq;		/* I: the owning workqueue */

	int			work_color;	/* L: current color */

	int			flush_color;	/* L: flushing color */

	int			nr_in_flight[WORK_NR_COLORS];

						/* L: nr of in_flight works */

	struct task_struct	*thread;

};



/*
@@ -214,6 +223,9 @@ static inline void debug_work_deactivate(struct work_struct *work) { } 
/* Serializes the accesses to the list of workqueues. */

static DEFINE_SPINLOCK(workqueue_lock);

static LIST_HEAD(workqueues);

static DEFINE_PER_CPU(struct ida, worker_ida);



static int worker_thread(void *__worker);



static int singlethread_cpu __read_mostly;
@@ -428,6 +440,105 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, 
}

EXPORT_SYMBOL_GPL(queue_delayed_work_on);



static struct worker *alloc_worker(void)

{

	struct worker *worker;



	worker = kzalloc(sizeof(*worker), GFP_KERNEL);

	return worker;

}



/**

 * create_worker - create a new workqueue worker

 * @cwq: cwq the new worker will belong to

 * @bind: whether to set affinity to @cpu or not

 *

 * Create a new worker which is bound to @cwq.  The returned worker

 * can be started by calling start_worker() or destroyed using

 * destroy_worker().

 *

 * CONTEXT:

 * Might sleep.  Does GFP_KERNEL allocations.

 *

 * RETURNS:

 * Pointer to the newly created worker.

 */

static struct worker *create_worker(struct cpu_workqueue_struct *cwq, bool bind)

{

	int id = -1;

	struct worker *worker = NULL;



	spin_lock(&workqueue_lock);

	while (ida_get_new(&per_cpu(worker_ida, cwq->cpu), &id)) {

		spin_unlock(&workqueue_lock);

		if (!ida_pre_get(&per_cpu(worker_ida, cwq->cpu), GFP_KERNEL))

			goto fail;

		spin_lock(&workqueue_lock);

	}

	spin_unlock(&workqueue_lock);



	worker = alloc_worker();

	if (!worker)

		goto fail;



	worker->cwq = cwq;

	worker->id = id;



	worker->task = kthread_create(worker_thread, worker, "kworker/%u:%d",

				      cwq->cpu, id);

	if (IS_ERR(worker->task))

		goto fail;



	if (bind)

		kthread_bind(worker->task, cwq->cpu);



	return worker;

fail:

	if (id >= 0) {

		spin_lock(&workqueue_lock);

		ida_remove(&per_cpu(worker_ida, cwq->cpu), id);

		spin_unlock(&workqueue_lock);

	}

	kfree(worker);

	return NULL;

}



/**

 * start_worker - start a newly created worker

 * @worker: worker to start

 *

 * Start @worker.

 *

 * CONTEXT:

 * spin_lock_irq(cwq->lock).

 */

static void start_worker(struct worker *worker)

{

	wake_up_process(worker->task);

}



/**

 * destroy_worker - destroy a workqueue worker

 * @worker: worker to be destroyed

 *

 * Destroy @worker.

 */

static void destroy_worker(struct worker *worker)

{

	int cpu = worker->cwq->cpu;

	int id = worker->id;



	/* sanity check frenzy */

	BUG_ON(worker->current_work);



	kthread_stop(worker->task);

	kfree(worker);



	spin_lock(&workqueue_lock);

	ida_remove(&per_cpu(worker_ida, cpu), id);

	spin_unlock(&workqueue_lock);

}



/**

 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight

 * @cwq: cwq of interest
@@ -468,7 +579,7 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) 


/**

 * process_one_work - process single work

 * @cwq: cwq to process work for

 * @worker: self

 * @work: work to process

 *

 * Process @work.  This function contains all the logics necessary to
@@ -480,9 +591,9 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) 
 * CONTEXT:

 * spin_lock_irq(cwq->lock) which is released and regrabbed.

 */

static void process_one_work(struct cpu_workqueue_struct *cwq,

			     struct work_struct *work)

static void process_one_work(struct worker *worker, struct work_struct *work)

{

	struct cpu_workqueue_struct *cwq = worker->cwq;

	work_func_t f = work->func;

	int work_color;

#ifdef CONFIG_LOCKDEP
@@ -497,7 +608,7 @@ static void process_one_work(struct cpu_workqueue_struct *cwq, 
#endif

	/* claim and process */

	debug_work_deactivate(work);

	cwq->current_work = work;

	worker->current_work = work;

	work_color = get_work_color(work);

	list_del_init(&work->entry);
@@ -524,30 +635,33 @@ static void process_one_work(struct cpu_workqueue_struct *cwq, 
	spin_lock_irq(&cwq->lock);



	/* we're done with it, release */

	cwq->current_work = NULL;

	worker->current_work = NULL;

	cwq_dec_nr_in_flight(cwq, work_color);

}



static void run_workqueue(struct cpu_workqueue_struct *cwq)

static void run_workqueue(struct worker *worker)

{

	struct cpu_workqueue_struct *cwq = worker->cwq;



	spin_lock_irq(&cwq->lock);

	while (!list_empty(&cwq->worklist)) {

		struct work_struct *work = list_entry(cwq->worklist.next,

						struct work_struct, entry);

		process_one_work(cwq, work);

		process_one_work(worker, work);

	}

	spin_unlock_irq(&cwq->lock);

}



/**

 * worker_thread - the worker thread function

 * @__cwq: cwq to serve

 * @__worker: self

 *

 * The cwq worker thread function.

 */

static int worker_thread(void *__cwq)

static int worker_thread(void *__worker)

{

	struct cpu_workqueue_struct *cwq = __cwq;

	struct worker *worker = __worker;

	struct cpu_workqueue_struct *cwq = worker->cwq;

	DEFINE_WAIT(wait);



	if (cwq->wq->flags & WQ_FREEZEABLE)
@@ -566,11 +680,11 @@ static int worker_thread(void *__cwq) 
		if (kthread_should_stop())

			break;



		if (unlikely(!cpumask_equal(&cwq->thread->cpus_allowed,

		if (unlikely(!cpumask_equal(&worker->task->cpus_allowed,

					    get_cpu_mask(cwq->cpu))))

			set_cpus_allowed_ptr(cwq->thread,

			set_cpus_allowed_ptr(worker->task,

					     get_cpu_mask(cwq->cpu));

		run_workqueue(cwq);

		run_workqueue(worker);

	}



	return 0;
@@ -873,7 +987,7 @@ int flush_work(struct work_struct *work) 
			goto already_gone;

		prev = &work->entry;

	} else {

		if (cwq->current_work != work)

		if (!cwq->worker || cwq->worker->current_work != work)

			goto already_gone;

		prev = &cwq->worklist;

	}
@@ -937,7 +1051,7 @@ static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq, 
	int running = 0;



	spin_lock_irq(&cwq->lock);

	if (unlikely(cwq->current_work == work)) {

	if (unlikely(cwq->worker && cwq->worker->current_work == work)) {

		insert_wq_barrier(cwq, &barr, cwq->worklist.next);

		running = 1;

	}
@@ -1225,7 +1339,7 @@ int current_is_keventd(void) 
	BUG_ON(!keventd_wq);



	cwq = get_cwq(cpu, keventd_wq);

	if (current == cwq->thread)

	if (current == cwq->worker->task)

		ret = 1;



	return ret;
@@ -1279,38 +1393,6 @@ static void free_cwqs(struct cpu_workqueue_struct *cwqs) 
#endif

}



static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)

{

	struct workqueue_struct *wq = cwq->wq;

	struct task_struct *p;



	p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);

	/*

	 * Nobody can add the work_struct to this cwq,

	 *	if (caller is __create_workqueue)

	 *		nobody should see this wq

	 *	else // caller is CPU_UP_PREPARE

	 *		cpu is not on cpu_online_map

	 * so we can abort safely.

	 */

	if (IS_ERR(p))

		return PTR_ERR(p);

	cwq->thread = p;



	return 0;

}



static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)

{

	struct task_struct *p = cwq->thread;



	if (p != NULL) {

		if (cpu >= 0)

			kthread_bind(p, cpu);

		wake_up_process(p);

	}

}



struct workqueue_struct *__create_workqueue_key(const char *name,

						unsigned int flags,

						struct lock_class_key *key,
@@ -1318,7 +1400,8 @@ struct workqueue_struct *__create_workqueue_key(const char *name, 
{

	bool singlethread = flags & WQ_SINGLE_THREAD;

	struct workqueue_struct *wq;

	int err = 0, cpu;

	bool failed = false;

	unsigned int cpu;



	wq = kzalloc(sizeof(*wq), GFP_KERNEL);

	if (!wq)
@@ -1348,20 +1431,21 @@ struct workqueue_struct *__create_workqueue_key(const char *name, 
		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);



		BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);

		cwq->wq = wq;

		cwq->cpu = cpu;

		cwq->wq = wq;

		cwq->flush_color = -1;

		spin_lock_init(&cwq->lock);

		INIT_LIST_HEAD(&cwq->worklist);

		init_waitqueue_head(&cwq->more_work);



		if (err)

		if (failed)

			continue;

		err = create_workqueue_thread(cwq, cpu);

		if (cpu_online(cpu) && !singlethread)

			start_workqueue_thread(cwq, cpu);

		cwq->worker = create_worker(cwq,

					    cpu_online(cpu) && !singlethread);

		if (cwq->worker)

			start_worker(cwq->worker);

		else

			start_workqueue_thread(cwq, -1);

			failed = true;

	}



	spin_lock(&workqueue_lock);
@@ -1370,7 +1454,7 @@ struct workqueue_struct *__create_workqueue_key(const char *name, 


	cpu_maps_update_done();



	if (err) {

	if (failed) {

		destroy_workqueue(wq);

		wq = NULL;

	}
@@ -1406,9 +1490,9 @@ void destroy_workqueue(struct workqueue_struct *wq) 
		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);

		int i;



		if (cwq->thread) {

			kthread_stop(cwq->thread);

			cwq->thread = NULL;

		if (cwq->worker) {

			destroy_worker(cwq->worker);

			cwq->worker = NULL;

		}



		for (i = 0; i < WORK_NR_COLORS; i++)
@@ -1495,6 +1579,11 @@ EXPORT_SYMBOL_GPL(work_on_cpu); 


void __init init_workqueues(void)

{

	unsigned int cpu;



	for_each_possible_cpu(cpu)

		ida_init(&per_cpu(worker_ida, cpu));



	singlethread_cpu = cpumask_first(cpu_possible_mask);

	hotcpu_notifier(workqueue_cpu_callback, 0);

	keventd_wq = create_workqueue("events");