linux-kernel - Re: [patch] irq: do not mask interrupts by default

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Date:	Tue, 14 Nov 2006 21:43:22 +0900 (JST)
From:	Komuro <komurojun-mbn@...ty.com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...l.org>,
	Komuro <komurojun-mbn@...ty.com>, tglx@...utronix.de,
	Adrian Bunk <bunk@...sta.de>, Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch] irq: do not mask interrupts by default

Dear Ingo

I tried your patch with 2.6.19-rc5.

The irq is generated properly.


Thanks!

Best Regards
Komuro


>>
>------------>
>Subject: irq: do not mask interrupts by default
>From: Ingo Molnar <mingo@...e.hu>
>
>never mask interrupts immediately upon request. Disabling
>interrupts in high-performance codepaths is rare, and on
>the other hand this change could recover lost edges (or
>even other types of lost interrupts) by conservatively
>only masking interrupts after they happen. (NOTE: with
>this change the highlevel irq-disable code still soft-disables
>this IRQ line - and if such an interrupt happens then the
>IRQ flow handler keeps the IRQ masked.)
>
>Signed-off-by: Ingo Molnar <mingo@...e.hu>
>---
> kernel/irq/chip.c |   13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
>Index: linux/kernel/irq/chip.c
>===================================================================
>--- linux.orig/kernel/irq/chip.c
>+++ linux/kernel/irq/chip.c
>@@ -202,10 +202,6 @@ static void default_enable(unsigned int 
>  */
> static void default_disable(unsigned int irq)
> {
>-	struct irq_desc *desc = irq_desc + irq;
>-
>-	if (!(desc->status & IRQ_DELAYED_DISABLE))
>-		desc->chip->mask(irq);
> }
> 
> /*
>@@ -272,8 +268,11 @@ handle_simple_irq(unsigned int irq, stru
> 	kstat_cpu(cpu).irqs[irq]++;
> 
> 	action = desc->action;
>-	if (unlikely(!action || (desc->status & IRQ_DISABLED)))
>+	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
>+		if (desc->chip->mask)
>+			desc->chip->mask(irq);
> 		goto out_unlock;
>+	}
> 
> 	desc->status |= IRQ_INPROGRESS;
> 	spin_unlock(&desc->lock);
>@@ -366,11 +365,13 @@ handle_fasteoi_irq(unsigned int irq, str
> 
> 	/*
> 	 * If its disabled or no action available
>-	 * keep it masked and get out of here
>+	 * then mask it and get out of here:
> 	 */
> 	action = desc->action;
> 	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
> 		desc->status |= IRQ_PENDING;
>+		if (desc->chip->mask)
>+			desc->chip->mask(irq);
> 		goto out;
> 	}
> 
>
>

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