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

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Date:   Mon, 11 Feb 2019 14:16:12 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     thesven73@...il.com
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] Input: qt2160 - remove redundant spinlock

On Sun, Feb 10, 2019 at 09:32:22PM -0500, thesven73@...il.com wrote:
> From: Sven Van Asbroeck <TheSven73@...il.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@...nel.org>
> Signed-off-by: Sven Van Asbroeck <TheSven73@...il.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