From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 19 Jun 2017 23:37:53 +0000 (+0200)
Subject: genirq/cpuhotplug: Avoid irq affinity setting for single targets
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8f31a9845db348f5781df47ce04c79e4cfe90016;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

genirq/cpuhotplug: Avoid irq affinity setting for single targets

Avoid trying to add a newly online CPU to the effective affinity mask of an
started up interrupt. That interrupt will either stay on the already online
CPU or move around for no value.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170619235447.431321047@linutronix.de
---

diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index b7964e72ded7..aee8f7ec40af 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -148,9 +148,17 @@ static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned int cpu)
 	    !irq_data_get_irq_chip(data) || !cpumask_test_cpu(cpu, affinity))
 		return;
 
-	if (irqd_is_managed_and_shutdown(data))
+	if (irqd_is_managed_and_shutdown(data)) {
 		irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
-	else
+		return;
+	}
+
+	/*
+	 * If the interrupt can only be directed to a single target
+	 * CPU then it is already assigned to a CPU in the affinity
+	 * mask. No point in trying to move it around.
+	 */
+	if (!irqd_is_single_target(data))
 		irq_set_affinity_locked(data, affinity, false);
 }