linux-kernel - Re: [PATCH] Revert lazy irq disable for simple irqs

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Date:	Thu, 13 Dec 2007 12:01:44 +0100
From:	"Remy Bohmer" <linux@...mer.net>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Russell King" <rmk+lkml@....linux.org.uk>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Daniel Walker" <dwalker@...sta.com>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Revert lazy irq disable for simple irqs

Hello Steven,

> In commit 76d2160147f43f982dfe881404cfde9fd0a9da21 lazy irq disabling
> was implemented, and the simple irq handler had a masking set to it.
>
> Remy Bohmer discovered that some devices in the ARM architecture
> would trigger the mask, but never unmask it. His patch to do the
> unmasking was questioned by Russell King about masking simple irqs
> to begin with. Looking further, it was discovered that the problems
> Remy was seeing was due to improper use of the simple handler by
> devices, and he later submitted patches to fix those. But the issue
> that was uncovered was that the simple handler should never mask.
>
> This patch reverts the masking in the simple handler.
>
Acked-by: Remy Bohmer <linux@...mer.net>




> ---
>  kernel/irq/chip.c |    9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
>
> Index: linux-compile.git/kernel/irq/chip.c
> ===================================================================
> --- linux-compile.git.orig/kernel/irq/chip.c    2007-10-19 12:37:51.000000000 -0400
> +++ linux-compile.git/kernel/irq/chip.c 2007-12-12 15:03:43.000000000 -0500
> @@ -297,18 +297,13 @@ handle_simple_irq(unsigned int irq, stru
>
>         if (unlikely(desc->status & IRQ_INPROGRESS))
>                 goto out_unlock;
> +       desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
>         kstat_cpu(cpu).irqs[irq]++;
>
>         action = desc->action;
> -       if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
> -               if (desc->chip->mask)
> -                       desc->chip->mask(irq);
> -               desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
> -               desc->status |= IRQ_PENDING;
> +       if (unlikely(!action || (desc->status & IRQ_DISABLED)))
>                 goto out_unlock;
> -       }
>
> -       desc->status &= ~(IRQ_REPLAY | IRQ_WAITING | IRQ_PENDING);
>         desc->status |= IRQ_INPROGRESS;
>         spin_unlock(&desc->lock);
>
>
>
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