Commit c44f2420 authored by Dmitry Torokhov's avatar Dmitry Torokhov
Browse files

Input: gameport - convert to use common workqueue instead of a thread 



Instead of creating an exclusive thread to handle gameport events (which
happen rarely), let's switch to common workqueue. With the arrival
of concurrency-managed workqueue infrastructure we are not concerned
that our callers or callees also using workqueue (no deadlocks anymore)
and it should reduce total number of threads in the system.

Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent 8ee294cd

drivers/input/gameport/gameport.c

+68 −84
Original line number Diff line number Diff line
@@ -18,13 +18,11 @@ 
#include <linux/ioport.h>

#include <linux/init.h>

#include <linux/gameport.h>

#include <linux/wait.h>

#include <linux/slab.h>

#include <linux/delay.h>

#include <linux/kthread.h>

#include <linux/workqueue.h>

#include <linux/sched.h>	/* HZ */

#include <linux/mutex.h>

#include <linux/freezer.h>



/*#include <asm/io.h>*/
@@ -234,58 +232,22 @@ struct gameport_event { 


static DEFINE_SPINLOCK(gameport_event_lock);	/* protects gameport_event_list */

static LIST_HEAD(gameport_event_list);

static DECLARE_WAIT_QUEUE_HEAD(gameport_wait);

static struct task_struct *gameport_task;



static int gameport_queue_event(void *object, struct module *owner,

				enum gameport_event_type event_type)

static struct gameport_event *gameport_get_event(void)

{

	struct gameport_event *event = NULL;

	unsigned long flags;

	struct gameport_event *event;

	int retval = 0;



	spin_lock_irqsave(&gameport_event_lock, flags);



	/*

	 * Scan event list for the other events for the same gameport port,

	 * starting with the most recent one. If event is the same we

	 * do not need add new one. If event is of different type we

	 * need to add this event and should not look further because

	 * we need to preseve sequence of distinct events.

	 */

	list_for_each_entry_reverse(event, &gameport_event_list, node) {

		if (event->object == object) {

			if (event->type == event_type)

				goto out;

			break;

		}

	}



	event = kmalloc(sizeof(struct gameport_event), GFP_ATOMIC);

	if (!event) {

		pr_err("Not enough memory to queue event %d\n", event_type);

		retval = -ENOMEM;

		goto out;

	}



	if (!try_module_get(owner)) {

		pr_warning("Can't get module reference, dropping event %d\n",

			   event_type);

		kfree(event);

		retval = -EINVAL;

		goto out;

	if (!list_empty(&gameport_event_list)) {

		event = list_first_entry(&gameport_event_list,

					 struct gameport_event, node);

		list_del_init(&event->node);

	}



	event->type = event_type;

	event->object = object;

	event->owner = owner;



	list_add_tail(&event->node, &gameport_event_list);

	wake_up(&gameport_wait);



out:

	spin_unlock_irqrestore(&gameport_event_lock, flags);

	return retval;

	return event;

}



static void gameport_free_event(struct gameport_event *event)
@@ -319,24 +281,8 @@ static void gameport_remove_duplicate_events(struct gameport_event *event) 
	spin_unlock_irqrestore(&gameport_event_lock, flags);

}



static struct gameport_event *gameport_get_event(void)

{

	struct gameport_event *event = NULL;

	unsigned long flags;



	spin_lock_irqsave(&gameport_event_lock, flags);



	if (!list_empty(&gameport_event_list)) {

		event = list_first_entry(&gameport_event_list,

					 struct gameport_event, node);

		list_del_init(&event->node);

	}



	spin_unlock_irqrestore(&gameport_event_lock, flags);

	return event;

}



static void gameport_handle_event(void)

static void gameport_handle_events(struct work_struct *work)

{

	struct gameport_event *event;
@@ -368,6 +314,59 @@ static void gameport_handle_event(void) 
	mutex_unlock(&gameport_mutex);

}



static DECLARE_WORK(gameport_event_work, gameport_handle_events);



static int gameport_queue_event(void *object, struct module *owner,

				enum gameport_event_type event_type)

{

	unsigned long flags;

	struct gameport_event *event;

	int retval = 0;



	spin_lock_irqsave(&gameport_event_lock, flags);



	/*

	 * Scan event list for the other events for the same gameport port,

	 * starting with the most recent one. If event is the same we

	 * do not need add new one. If event is of different type we

	 * need to add this event and should not look further because

	 * we need to preserve sequence of distinct events.

	 */

	list_for_each_entry_reverse(event, &gameport_event_list, node) {

		if (event->object == object) {

			if (event->type == event_type)

				goto out;

			break;

		}

	}



	event = kmalloc(sizeof(struct gameport_event), GFP_ATOMIC);

	if (!event) {

		pr_err("Not enough memory to queue event %d\n", event_type);

		retval = -ENOMEM;

		goto out;

	}



	if (!try_module_get(owner)) {

		pr_warning("Can't get module reference, dropping event %d\n",

			   event_type);

		kfree(event);

		retval = -EINVAL;

		goto out;

	}



	event->type = event_type;

	event->object = object;

	event->owner = owner;



	list_add_tail(&event->node, &gameport_event_list);

	schedule_work(&gameport_event_work);



out:

	spin_unlock_irqrestore(&gameport_event_lock, flags);

	return retval;

}



/*

 * Remove all events that have been submitted for a given object,

 * be it a gameport port or a driver.
@@ -419,19 +418,6 @@ static struct gameport *gameport_get_pending_child(struct gameport *parent) 
	return child;

}



static int gameport_thread(void *nothing)

{

	set_freezable();

	do {

		gameport_handle_event();

		wait_event_freezable(gameport_wait,

			kthread_should_stop() || !list_empty(&gameport_event_list));

	} while (!kthread_should_stop());



	return 0;

}





/*

 * Gameport port operations

 */
@@ -814,13 +800,6 @@ static int __init gameport_init(void) 
		return error;

	}



	gameport_task = kthread_run(gameport_thread, NULL, "kgameportd");

	if (IS_ERR(gameport_task)) {

		bus_unregister(&gameport_bus);

		error = PTR_ERR(gameport_task);

		pr_err("Failed to start kgameportd, error: %d\n", error);

		return error;

	}



	return 0;

}
@@ -828,7 +807,12 @@ static int __init gameport_init(void) 
static void __exit gameport_exit(void)

{

	bus_unregister(&gameport_bus);

	kthread_stop(gameport_task);



	/*

	 * There should not be any outstanding events but work may

	 * still be scheduled so simply cancel it.

	 */

	cancel_work_sync(&gameport_event_work);

}



subsys_initcall(gameport_init);

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