[4.2.y-ckt stable] Patch "x86/apic: Handle zero vector gracefully in clear_vector_irq()" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    x86/apic: Handle zero vector gracefully in clear_vector_irq()

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt10.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 810a427af6ba7a1579949b3435d4165fe1e434d3 Mon Sep 17 00:00:00 2001
From: Keith Busch <keith.busch at intel.com>
Date: Wed, 27 Apr 2016 14:22:32 -0600
Subject: x86/apic: Handle zero vector gracefully in clear_vector_irq()

commit 1bdb8970392a68489b469c3a330a1adb5ef61beb upstream.

If x86_vector_alloc_irq() fails x86_vector_free_irqs() is invoked to cleanup
the already allocated vectors. This subsequently calls clear_vector_irq().

The failed irq has no vector assigned, which triggers the BUG_ON(!vector) in
clear_vector_irq().

We cannot suppress the call to x86_vector_free_irqs() for the failed
interrupt, because the other data related to this irq must be cleaned up as
well. So calling clear_vector_irq() with vector == 0 is legitimate.

Remove the BUG_ON and return if vector is zero,

[ tglx: Massaged changelog ]

Fixes: b5dc8e6c21e7 "x86/irq: Use hierarchical irqdomain to manage CPU interrupt vectors"
Signed-off-by: Keith Busch <keith.busch at intel.com>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/kernel/apic/vector.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 7889bec..c8a2b9c 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -226,7 +226,8 @@ static void clear_irq_vector(int irq, struct apic_chip_data *data)
 {
 	int cpu, vector;

-	BUG_ON(!data->cfg.vector);
+	if (!data->cfg.vector)
+		return;

 	vector = data->cfg.vector;
 	for_each_cpu_and(cpu, data->domain, cpu_online_mask)
--
2.7.4