[PATCH] rtc-ds1305: Use disable_irq_nosync() from within irq handlers.

[PATCH] rtc-ds1305: Use disable_irq_nosync() from within irq handlers.

[Ben Nizette]

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@niasdigital.com>
---
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

Re: [PATCH] rtc-ds1305: Use disable_irq_nosync() from within irq handlers.

[David Brownell]

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@niasdigital.com>

Acked-by: David Brownell <dbrownell@users.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
> 
> 
> 
>