[3.13.y.z extended stable] Patch "arm64: use irq_set_affinity with force=false when migrating irqs" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Wed Oct 8 22:14:03 UTC 2014


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

    arm64: use irq_set_affinity with force=false when migrating irqs

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.9.

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

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 20f111c9f36ccf839e94132883a89781c2a7ef55 Mon Sep 17 00:00:00 2001
From: Sudeep Holla <sudeep.holla at arm.com>
Date: Tue, 2 Sep 2014 11:35:24 +0100
Subject: arm64: use irq_set_affinity with force=false when migrating irqs

commit 3d8afe3099ebc602848aa7f09235cce3a9a023ce upstream.

The arm64 interrupt migration code on cpu offline calls
irqchip.irq_set_affinity() with the argument force=true. Originally
this argument had no effect because it was not used by any interrupt
chip driver and there was no semantics defined.

This changed with commit 01f8fa4f01d8 ("genirq: Allow forcing cpu
affinity of interrupts") which made the force argument useful to route
interrupts to not yet online cpus without checking the target cpu
against the cpu online mask. The following commit ffde1de64012
("irqchip: gic: Support forced affinity setting") implemented this for
the GIC interrupt controller.

As a consequence the cpu offline irq migration fails if CPU0 is
offlined, because CPU0 is still set in the affinity mask and the
validation against cpu online mask is skipped to the force argument
being true. The following first_cpu(mask) selection always selects
CPU0 as the target.

Commit 601c942176d8("arm64: use cpu_online_mask when using forced
irq_set_affinity") intended to fix the above mentioned issue but
introduced another issue where affinity can be migrated to a wrong
CPU due to unconditional copy of cpu_online_mask.

As with for arm, solve the issue by calling irq_set_affinity() with
force=false from the CPU offline irq migration code so the GIC driver
validates the affinity mask against CPU online mask and therefore
removes CPU0 from the possible target candidates. Also revert the
changes done in the commit 601c942176d8 as it's no longer needed.

Tested on Juno platform.

Fixes: 601c942176d8("arm64: use cpu_online_mask when using forced
	irq_set_affinity")
Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
Acked-by: Mark Rutland <mark.rutland at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
[ kamal: backport to 3.13-stable: only need the irq_set_affinity(false) fix ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm64/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index 473e5db..dfa6e3e 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -105,7 +105,7 @@ static bool migrate_one_irq(struct irq_desc *desc)
 	c = irq_data_get_irq_chip(d);
 	if (!c->irq_set_affinity)
 		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
-	else if (c->irq_set_affinity(d, affinity, true) == IRQ_SET_MASK_OK && ret)
+	else if (c->irq_set_affinity(d, affinity, false) == IRQ_SET_MASK_OK && ret)
 		cpumask_copy(d->affinity, affinity);

 	return ret;
--
1.9.1





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