diff options
authorThomas Gleixner <tglx@linutronix.de>2017-07-27 12:21:11 +0200
committerThomas Gleixner <tglx@linutronix.de>2017-07-27 15:40:02 +0200
commit8397913303abc9333f376a518a8368fa22ca5e6e (patch)
parentda08f35b0f82b0a7a79f518faf8d0c0b477f91bc (diff)
genirq/cpuhotplug: Revert "Set force affinity flag on hotplug migration"
That commit was part of the changes moving x86 to the generic CPU hotplug interrupt migration code. The force flag was required on x86 before the hierarchical irqdomain rework, but invoking set_affinity() with force=true stayed and had no side effects. At some point in the past, the force flag got repurposed to support the exynos timer interrupt affinity setting to a not yet online CPU, so the interrupt controller callback does not verify the supplied affinity mask against cpu_online_mask. Setting the flag in the CPU hotplug code causes the cpu online masking to be blocked on these irq controllers and results in potentially affining an interrupt to the CPU which is unplugged, i.e. instead of moving it away, it's just reassigned to it. As the force flags is not longer needed on x86, it's safe to revert that patch so the ARM irqchips which use the force flag work again. Add comments to that effect, so this won't happen again. Note: The online mask handling should be done in the generic code and the force flag and the masking in the irq chips removed all together, but that's not a change possible for 4.13. Fixes: 77f85e66aa8b ("genirq/cpuhotplug: Set force affinity flag on hotplug migration") Reported-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Will Deacon <will.deacon@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: LAK <linux-arm-kernel@lists.infradead.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1707271217590.3109@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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);