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[PATCH 3.16.y-ckt 03/58] MIPS: IRQ: Fix disable_irq on CPU IRQs

To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com
Subject: [PATCH 3.16.y-ckt 03/58] MIPS: IRQ: Fix disable_irq on CPU IRQs
From: Luis Henriques <luis.henriques@canonical.com>
Date: Thu, 19 Feb 2015 13:51:33 +0000
Cc: Felix Fietkau <nbd@openwrt.org>, linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>, Luis Henriques <luis.henriques@canonical.com>
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3.16.7-ckt7 -stable review patch.  If anyone has any objections, please let me 
know.

------------------

From: Felix Fietkau <nbd@openwrt.org>

commit a3e6c1eff54878506b2dddcc202df9cc8180facb upstream.

If the irq_chip does not define .irq_disable, any call to disable_irq
will defer disabling the IRQ until it fires while marked as disabled.
This assumes that the handler function checks for this condition, which
handle_percpu_irq does not. In this case, calling disable_irq leads to
an IRQ storm, if the interrupt fires while disabled.

This optimization is only useful when disabling the IRQ is slow, which
is not true for the MIPS CPU IRQ.

Disable this optimization by implementing .irq_disable and .irq_enable

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8949/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 arch/mips/kernel/irq_cpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/mips/kernel/irq_cpu.c b/arch/mips/kernel/irq_cpu.c
index e498f2b3646a..f5598e25e906 100644
--- a/arch/mips/kernel/irq_cpu.c
+++ b/arch/mips/kernel/irq_cpu.c
@@ -56,6 +56,8 @@ static struct irq_chip mips_cpu_irq_controller = {
        .irq_mask_ack   = mask_mips_irq,
        .irq_unmask     = unmask_mips_irq,
        .irq_eoi        = unmask_mips_irq,
+       .irq_disable    = mask_mips_irq,
+       .irq_enable     = unmask_mips_irq,
 };
 
 /*
@@ -92,6 +94,8 @@ static struct irq_chip mips_mt_cpu_irq_controller = {
        .irq_mask_ack   = mips_mt_cpu_irq_ack,
        .irq_unmask     = unmask_mips_irq,
        .irq_eoi        = unmask_mips_irq,
+       .irq_disable    = mask_mips_irq,
+       .irq_enable     = unmask_mips_irq,
 };
 
 void __init mips_cpu_irq_init(void)
-- 
2.1.4


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