linux-kernel - Re: [PATCH] rtc-ds1305: Use disable_irq

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Message-Id: <200904160931.33419.david-b@pacbell.net>
Date:	Thu, 16 Apr 2009 09:31:33 -0700
From:	David Brownell <david-b@...bell.net>
To:	Ben Nizette <bn@...sdigital.com>
Cc:	p_gortmaker@...oo.com,
	"linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rtc-ds1305: Use disable_irq_nosync() from within irq handlers.

On Wednesday 15 April 2009, Ben Nizette wrote:
> 
> disable_irq() should wait for all running handlers to complete
> before returning.  As such, if it's used to disable an interrupt
> from that interrupt's handler it will deadlock.  This replaces
> the dangerous instances with the _nosync() variant which doesn't
> have this problem.
> 
> Signed-off-by: Ben Nizette <bn@...sdigital.com>

Acked-by: David Brownell <dbrownell@...rs.sourceforge.net>

Also ... it would be nice to convert this driver to the
new request_threaded_irq() infrastructure.  The board I
had with this chip has a busted ttyS0 *input* line, so it's
not much use for development any more; or I'd update it
myself, it's a simple change.  Someone with that hardware
should think about spending the few minutes needed to make
and test that patch.


> ---
> diff --git a/drivers/rtc/rtc-ds1305.c b/drivers/rtc/rtc-ds1305.c
> index fc372df..5c4f789 100644
> --- a/drivers/rtc/rtc-ds1305.c
> +++ b/drivers/rtc/rtc-ds1305.c
> @@ -514,7 +514,7 @@ static irqreturn_t ds1305_irq(int irq, void *p)
>  {
>  	struct ds1305		*ds1305 = p;
>  
> -	disable_irq(irq);
> +	disable_irq_nosync(irq);
>  	schedule_work(&ds1305->work);
>  	return IRQ_HANDLED;
>  }
> -- 
> 1.6.0.2
> 
> 
> 
> 



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