linux-kernel - [PATCH RT] add pending in fasteoi for IOAPIC hack

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Date:	Wed, 12 Dec 2007 15:41:00 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH RT] add pending in fasteoi for IOAPIC hack


The IOAPIC hack that does a level=>edge to mask does not disable
interrupts. So we can receive interrupts when masked, and this means
that we can miss interrupts that arrive when the thread is handling
them.

This patch adds the "IRQ_PENDING" logic of the edge irqs to be
able to catch interrupts coming in when supposably "masked".

Signed-off-by: Steven Rostedt <srostedt@...hat.com>

Index: linux-2.6.21-rt-hack/kernel/irq/chip.c
===================================================================
--- linux-2.6.21-rt-hack.orig/kernel/irq/chip.c
+++ linux-2.6.21-rt-hack/kernel/irq/chip.c
@@ -398,8 +398,10 @@ handle_fasteoi_irq(unsigned int irq, str

 	spin_lock(&desc->lock);

-	if (unlikely(desc->status & IRQ_INPROGRESS))
+	if (unlikely(desc->status & IRQ_INPROGRESS)) {
+		desc->status |= IRQ_PENDING;
 		goto out;
+	}

 	desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
 	kstat_cpu(cpu).irqs[irq]++;


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