linux-kernel - Re: Device hang when offlining a CPU due to IRQ misrouting

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Date:	Tue, 19 Jun 2007 12:59:27 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	"Darrick J. Wong" <djwong@...ibm.com>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Device hang when offlining a CPU due to IRQ misrouting

On Tue, Jun 19, 2007 at 12:06:37PM -0700, Darrick J. Wong wrote:
> On Tue, Jun 19, 2007 at 11:00:03AM -0700, Siddha, Suresh B wrote:
> > Anyhow, Darrick there is a general bug in this area, can you try this and
> > see if it helps?
> 
> Er... that instantly locked up the system.

hmm.. Please try this instead. This is intended only for debug. Based on your
test results, we can comeup with a more decent fix.

diff --git a/arch/x86_64/kernel/irq.c b/arch/x86_64/kernel/irq.c
index 3eaceac..3997679 100644
--- a/arch/x86_64/kernel/irq.c
+++ b/arch/x86_64/kernel/irq.c
@@ -144,17 +144,37 @@ void fixup_irqs(cpumask_t map)
 
 	for (irq = 0; irq < NR_IRQS; irq++) {
 		cpumask_t mask;
+		int break_affinity = 0;
+		int set_affinity = 1;
+
 		if (irq == 2)
 			continue;
 
+		/* irq's are disabled at this point */
+		spin_lock(&irq_desc[irq].lock);
+
 		cpus_and(mask, irq_desc[irq].affinity, map);
 		if (any_online_cpu(mask) == NR_CPUS) {
-			printk("Breaking affinity for irq %i\n", irq);
+			break_affinity = 1;
 			mask = map;
 		}
+
+		if (irq_desc[irq].chip->mask)
+			irq_desc[irq].chip->mask(irq);
+
 		if (irq_desc[irq].chip->set_affinity)
 			irq_desc[irq].chip->set_affinity(irq, mask);
 		else if (irq_desc[irq].action && !(warned++))
+			set_affinity = 0;
+
+		if (irq_desc[irq].chip->unmask)
+			irq_desc[irq].chip->unmask(irq);
+
+		spin_unlock(&irq_desc[irq].lock);
+
+		if (break_affinity && set_affinity)
+			printk("Broke affinity for irq %i\n", irq);
+		else if (!set_affinity)
 			printk("Cannot set affinity for irq %i\n", irq);
 	}
 
-
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