linux-kernel - [GIT pull] irq fix for 4.13

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Date:   Sun, 30 Jul 2017 10:54:23 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [GIT pull] irq fix for 4.13

Linus,

please pull the latest irq-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq-urgent-for-linus


Fix for a regression caused by the conversion of x86 to the generic hotplug
code. Instead of doing a plain single line revert, this adds a pile of
comments so the semantics of the force argument are clear.

Thanks,

	tglx

------------------>
Thomas Gleixner (1):
      genirq/cpuhotplug: Revert "Set force affinity flag on hotplug migration"


 include/linux/irq.h     | 7 ++++++-
 kernel/irq/cpuhotplug.c | 9 +++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 00db35b61e9e..d2d543794093 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -388,7 +388,12 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
  * @irq_mask_ack:	ack and mask an interrupt source
  * @irq_unmask:		unmask an interrupt source
  * @irq_eoi:		end of interrupt
- * @irq_set_affinity:	set the CPU affinity on SMP machines
+ * @irq_set_affinity:	Set the CPU affinity on SMP machines. If the force
+ *			argument is true, it tells the driver to
+ *			unconditionally apply the affinity setting. Sanity
+ *			checks against the supplied affinity mask are not
+ *			required. This is used for CPU hotplug where the
+ *			target CPU is not yet set in the cpu_online_mask.
  * @irq_retrigger:	resend an IRQ to the CPU
  * @irq_set_type:	set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ
  * @irq_set_wake:	enable/disable power-management wake-on of an IRQ
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index aee8f7ec40af..638eb9c83d9f 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -95,8 +95,13 @@ static bool migrate_one_irq(struct irq_desc *desc)
 		affinity = cpu_online_mask;
 		brokeaff = true;
 	}
-
-	err = irq_do_set_affinity(d, affinity, true);
+	/*
+	 * Do not set the force argument of irq_do_set_affinity() as this
+	 * disables the masking of offline CPUs from the supplied affinity
+	 * mask and therefore might keep/reassign the irq to the outgoing
+	 * CPU.
+	 */
+	err = irq_do_set_affinity(d, affinity, false);
 	if (err) {
 		pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n",
 				    d->irq, err);