linux-kernel - Re: [PATCH] Optimize i8259 code a bit.

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Message-ID: <alpine.LFD.0.9999.0710281753000.3186@localhost.localdomain>
Date:	Sun, 28 Oct 2007 17:54:15 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ralf Baechle <ralf@...ux-mips.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Optimize i8259 code a bit.

On Sun, 28 Oct 2007, Ralf Baechle wrote:

> The timer code always calls the clock_event_device set_net_event and
> set_mode methods with interrupts disabled, so no need to use
> spin_lock_irqsave / spin_unlock_irqrestore for those.

Good point,

Acked-by:Thomas Gleixner <tglx@...utronix.de>


> diff --git a/arch/mips/kernel/i8253.c b/arch/mips/kernel/i8253.c
> index 5d9830d..1b54674 100644
> --- a/arch/mips/kernel/i8253.c
> +++ b/arch/mips/kernel/i8253.c
> @@ -23,9 +23,7 @@ static DEFINE_SPINLOCK(i8253_lock);
>  static void init_pit_timer(enum clock_event_mode mode,
>  			   struct clock_event_device *evt)
>  {
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&i8253_lock, flags);
> +	spin_lock(&i8253_lock);
>  
>  	switch(mode) {
>  	case CLOCK_EVT_MODE_PERIODIC:
> @@ -54,7 +52,7 @@ static void init_pit_timer(enum clock_event_mode mode,
>  		/* Nothing to do here */
>  		break;
>  	}
> -	spin_unlock_irqrestore(&i8253_lock, flags);
> +	spin_unlock(&i8253_lock);
>  }
>  
>  /*
> @@ -64,12 +62,10 @@ static void init_pit_timer(enum clock_event_mode mode,
>   */
>  static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
>  {
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&i8253_lock, flags);
> +	spin_lock(&i8253_lock);
>  	outb_p(delta & 0xff , PIT_CH0);	/* LSB */
>  	outb(delta >> 8 , PIT_CH0);	/* MSB */
> -	spin_unlock_irqrestore(&i8253_lock, flags);
> +	spin_unlock(&i8253_lock);
>  
>  	return 0;
>  }
> diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
> index a42c807..5246515 100644
> --- a/arch/x86/kernel/i8253.c
> +++ b/arch/x86/kernel/i8253.c
> @@ -31,9 +31,7 @@ struct clock_event_device *global_clock_event;
>  static void init_pit_timer(enum clock_event_mode mode,
>  			   struct clock_event_device *evt)
>  {
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&i8253_lock, flags);
> +	spin_lock(&i8253_lock);
>  
>  	switch(mode) {
>  	case CLOCK_EVT_MODE_PERIODIC:
> @@ -62,7 +60,7 @@ static void init_pit_timer(enum clock_event_mode mode,
>  		/* Nothing to do here */
>  		break;
>  	}
> -	spin_unlock_irqrestore(&i8253_lock, flags);
> +	spin_unlock(&i8253_lock);
>  }
>  
>  /*
> @@ -72,12 +70,10 @@ static void init_pit_timer(enum clock_event_mode mode,
>   */
>  static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
>  {
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&i8253_lock, flags);
> +	spin_lock(&i8253_lock);
>  	outb_p(delta & 0xff , PIT_CH0);	/* LSB */
>  	outb(delta >> 8 , PIT_CH0);	/* MSB */
> -	spin_unlock_irqrestore(&i8253_lock, flags);
> +	spin_unlock(&i8253_lock);
>  
>  	return 0;
>  }
> 
-
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