linux-kernel - Re: [-next] !irqd_can_balance() WARNINGs at irq_move_masked

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Date:	Fri, 19 Jun 2015 11:25:21 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [-next] !irqd_can_balance() WARNINGs at irq_move_masked_irq()

On Fri, 19 Jun 2015, Sergey Senozhatsky wrote:
> [    0.412291] WARNING: CPU: 0 PID: 0 at kernel/irq/migration.c:21 irq_move_masked_irq+0x57/0xc4()
> [    0.412371] Can't balance irq 0 [edge]

Yuck.

> Do you guys want to replace WAN_ON() with WARN_ONCE(), perhaps? This, of course,
> doesn't fix anything; but at least one can boot the system. (not really a patch,
> just an idea).

Indeed. We really want to clear the move pending bit before the can
balance check. Patch below. But that does not explain why this happens
in the first place.

Can you please send me a full dmesg, kernel config and output of
/proc/interrupts ? (Private mail is fine, or upload it to some place)

Thanks,

	tglx
---
diff --git a/kernel/irq/migration.c b/kernel/irq/migration.c
index dd203e276b07..8cf8c24afaab 100644
--- a/kernel/irq/migration.c
+++ b/kernel/irq/migration.c
@@ -12,16 +12,19 @@ void irq_move_masked_irq(struct irq_data *idata)
 	if (likely(!irqd_is_setaffinity_pending(&desc->irq_data)))
 		return;
 
+	irqd_clr_move_pending(&desc->irq_data);
+
 	/*
 	 * Paranoia: cpu-local interrupts shouldn't be calling in here anyway.
 	 */
 	if (!irqd_can_balance(&desc->irq_data)) {
-		WARN_ON(1);
+		pr_warn("Cannot move irq %d: %s\n",
+			desc->irq_data.irq,
+			irqd_is_per_cpu(&desc->irq_data) ?
+			"per cpu" : "balancing disabled");
 		return;
 	}
 
-	irqd_clr_move_pending(&desc->irq_data);
-
 	if (unlikely(cpumask_empty(desc->pending_mask)))
 		return;
 
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