[PATCH] Input: qt2160 - remove redundant spinlock

[PATCH] Input: qt2160 - remove redundant spinlock

[thesven73]

From: Sven Van Asbroeck <TheSven73@gmail.com>

Remove a spinlock which prevents schedule_delayed_work() and
mod_delayed_work() from executing concurrently.

This was required back when mod_delayed_work() did not exist,
and had to be implemented with a cancel + schedule. See
commit e7c2f967445d ("workqueue: use mod_delayed_work() instead of
__cancel + queue")

schedule_delayed_work() and mod_delayed_work() can now be used
concurrently. So the spinlock is no longer needed.

Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
---
 drivers/input/keyboard/qt2160.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/input/keyboard/qt2160.c b/drivers/input/keyboard/qt2160.c
index 43b86482dda0..23dc7c0c7d78 100644
--- a/drivers/input/keyboard/qt2160.c
+++ b/drivers/input/keyboard/qt2160.c
@@ -69,7 +69,6 @@ struct qt2160_data {
 	struct i2c_client *client;
 	struct input_dev *input;
 	struct delayed_work dwork;
-	spinlock_t lock;        /* Protects canceling/rescheduling of dwork */
 	unsigned short keycodes[ARRAY_SIZE(qt2160_key2code)];
 	u16 key_matrix;
 #ifdef CONFIG_LEDS_CLASS
@@ -221,22 +220,15 @@ static int qt2160_get_key_matrix(struct qt2160_data *qt2160)
 static irqreturn_t qt2160_irq(int irq, void *_qt2160)
 {
 	struct qt2160_data *qt2160 = _qt2160;
-	unsigned long flags;
-
-	spin_lock_irqsave(&qt2160->lock, flags);
 
 	mod_delayed_work(system_wq, &qt2160->dwork, 0);
 
-	spin_unlock_irqrestore(&qt2160->lock, flags);
-
 	return IRQ_HANDLED;
 }
 
 static void qt2160_schedule_read(struct qt2160_data *qt2160)
 {
-	spin_lock_irq(&qt2160->lock);
 	schedule_delayed_work(&qt2160->dwork, QT2160_CYCLE_INTERVAL);
-	spin_unlock_irq(&qt2160->lock);
 }
 
 static void qt2160_worker(struct work_struct *work)
@@ -406,7 +398,6 @@ static int qt2160_probe(struct i2c_client *client,
 	qt2160->client = client;
 	qt2160->input = input;
 	INIT_DELAYED_WORK(&qt2160->dwork, qt2160_worker);
-	spin_lock_init(&qt2160->lock);
 
 	input->name = "AT42QT2160 Touch Sense Keyboard";
 	input->id.bustype = BUS_I2C;
-- 
2.17.1

Re: [PATCH] Input: qt2160 - remove redundant spinlock

[Dmitry Torokhov]

On Sun, Feb 10, 2019 at 09:32:22PM -0500, thesven73@gmail.com wrote:
> From: Sven Van Asbroeck <TheSven73@gmail.com>
> 
> Remove a spinlock which prevents schedule_delayed_work() and
> mod_delayed_work() from executing concurrently.
> 
> This was required back when mod_delayed_work() did not exist,
> and had to be implemented with a cancel + schedule. See
> commit e7c2f967445d ("workqueue: use mod_delayed_work() instead of
> __cancel + queue")
> 
> schedule_delayed_work() and mod_delayed_work() can now be used
> concurrently. So the spinlock is no longer needed.
> 
> Cc: Tejun Heo <tj@kernel.org>
> Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>

Applied, thank you.

> ---
>  drivers/input/keyboard/qt2160.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> diff --git a/drivers/input/keyboard/qt2160.c b/drivers/input/keyboard/qt2160.c
> index 43b86482dda0..23dc7c0c7d78 100644
> --- a/drivers/input/keyboard/qt2160.c
> +++ b/drivers/input/keyboard/qt2160.c
> @@ -69,7 +69,6 @@ struct qt2160_data {
>  	struct i2c_client *client;
>  	struct input_dev *input;
>  	struct delayed_work dwork;
> -	spinlock_t lock;        /* Protects canceling/rescheduling of dwork */
>  	unsigned short keycodes[ARRAY_SIZE(qt2160_key2code)];
>  	u16 key_matrix;
>  #ifdef CONFIG_LEDS_CLASS
> @@ -221,22 +220,15 @@ static int qt2160_get_key_matrix(struct qt2160_data *qt2160)
>  static irqreturn_t qt2160_irq(int irq, void *_qt2160)
>  {
>  	struct qt2160_data *qt2160 = _qt2160;
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&qt2160->lock, flags);
>  
>  	mod_delayed_work(system_wq, &qt2160->dwork, 0);
>  
> -	spin_unlock_irqrestore(&qt2160->lock, flags);
> -
>  	return IRQ_HANDLED;
>  }
>  
>  static void qt2160_schedule_read(struct qt2160_data *qt2160)
>  {
> -	spin_lock_irq(&qt2160->lock);
>  	schedule_delayed_work(&qt2160->dwork, QT2160_CYCLE_INTERVAL);
> -	spin_unlock_irq(&qt2160->lock);
>  }
>  
>  static void qt2160_worker(struct work_struct *work)
> @@ -406,7 +398,6 @@ static int qt2160_probe(struct i2c_client *client,
>  	qt2160->client = client;
>  	qt2160->input = input;
>  	INIT_DELAYED_WORK(&qt2160->dwork, qt2160_worker);
> -	spin_lock_init(&qt2160->lock);
>  
>  	input->name = "AT42QT2160 Touch Sense Keyboard";
>  	input->id.bustype = BUS_I2C;
> -- 
> 2.17.1
> 

-- 
Dmitry