netdev - [patch] genirq: fix simple and fasteoi irq handlers

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Date:	Fri, 3 Aug 2007 08:07:33 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Gabriel C <nix.or.die@...glemail.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jean-Baptiste Vignaud <vignaud@...dmail.fr>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	shemminger <shemminger@...ux-foundation.org>,
	linux-net <linux-net@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, marcin.slusarz@...il.com
Subject: [patch] genirq: fix simple and fasteoi irq handlers

On Thu, Aug 02, 2007 at 10:11:26PM +0200, Ingo Molnar wrote:
> 
> * Gabriel C <nix.or.die@...glemail.com> wrote:
> 
> > I get a warning on each boot now with this patch ..
> > 
> > [   63.686613] WARNING: at kernel/irq/resend.c:70 check_irq_resend()
...
> we are still trying to figure out what happens with ne2k-pci. The 
> message will vanish soon.

Hi,

I can't guarantee this is all needed to fix this bug, but I think
this patch is necessary here.

Regards,
Jarek P.
------------>

Subject: genirq: fix simple and fasteoi irq handlers

After the "genirq: do not mask interrupts by default" patch interrupts
should be disabled not immediately upon request, but after they happen.
But, handle_simple_irq() and handle_fasteoi_irq() can skip this once or
more if an irq is just serviced (IRQ_INPROGRESS), possibly disrupting a
driver's work.

The main reason of problems here, pointing the broken patch and making
the first patch which can fix this was done by Marcin Slusarz.
Additional test patches of Thomas Gleixner and Ingo Molnar tested by
Marcin Slusarz helped to narrow possible reasons even more. Thanks.

PS: this patch fixes only one evident error here, but there could be
more places affected by above-mentioned change in irq handling.


Signed-off-by: Jarek Poplawski <jarkao2@...pl>

---

diff -Nurp 2.6.23-rc1-/kernel/irq/chip.c 2.6.23-rc1/kernel/irq/chip.c
--- 2.6.23-rc1-/kernel/irq/chip.c	2007-07-09 01:32:17.000000000 +0200
+++ 2.6.23-rc1/kernel/irq/chip.c	2007-08-02 20:42:38.000000000 +0200
@@ -295,12 +295,11 @@ handle_simple_irq(unsigned int irq, stru
 
 	spin_lock(&desc->lock);
 
-	if (unlikely(desc->status & IRQ_INPROGRESS))
-		goto out_unlock;
 	kstat_cpu(cpu).irqs[irq]++;
 
 	action = desc->action;
-	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
+	if (unlikely(!action || (desc->status & (IRQ_INPROGRESS |
+						 IRQ_DISABLED)))) {
 		if (desc->chip->mask)
 			desc->chip->mask(irq);
 		desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
@@ -392,18 +391,16 @@ handle_fasteoi_irq(unsigned int irq, str
 
 	spin_lock(&desc->lock);
 
-	if (unlikely(desc->status & IRQ_INPROGRESS))
-		goto out;
-
 	desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
 	kstat_cpu(cpu).irqs[irq]++;
 
 	/*
-	 * If its disabled or no action available
+	 * If it's running, disabled or no action available
 	 * then mask it and get out of here:
 	 */
 	action = desc->action;
-	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
+	if (unlikely(!action || (desc->status & (IRQ_INPROGRESS |
+						 IRQ_DISABLED)))) {
 		desc->status |= IRQ_PENDING;
 		if (desc->chip->mask)
 			desc->chip->mask(irq);
-
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