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authorThomas Gleixner <tglx@linutronix.de>2017-06-20 01:37:51 +0200
committerThomas Gleixner <tglx@linutronix.de>2017-06-22 18:21:25 +0200
commitc5cb83bb337c25caae995d992d1cdf9b317f83de (patch)
treead779ff06d57ac629b00fd097a6c93c8b0b6141e
parent761ea388e8c4e3ac883a94e16bcc8c51fa419d4f (diff)
downloadlinux-stericsson-c5cb83bb337c25caae995d992d1cdf9b317f83de.tar.gz
genirq/cpuhotplug: Handle managed IRQs on CPU hotplug
If a CPU goes offline, interrupts affine to the CPU are moved away. If the outgoing CPU is the last CPU in the affinity mask the migration code breaks the affinity and sets it it all online cpus. This is a problem for affinity managed interrupts as CPU hotplug is often used for power management purposes. If the affinity is broken, the interrupt is not longer affine to the CPUs to which it was allocated. The affinity spreading allows to lay out multi queue devices in a way that they are assigned to a single CPU or a group of CPUs. If the last CPU goes offline, then the queue is not longer used, so the interrupt can be shutdown gracefully and parked until one of the assigned CPUs comes online again. Add a graceful shutdown mechanism into the irq affinity breaking code path, mark the irq as MANAGED_SHUTDOWN and leave the affinity mask unmodified. In the online path, scan the active interrupts for managed interrupts and if the interrupt is functional and the newly online CPU is part of the affinity mask, restart the interrupt if it is marked MANAGED_SHUTDOWN or if the interrupts is started up, try to add the CPU back to the effective affinity mask. Originally-by: Christoph Hellwig <hch@lst.de> 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> Link: http://lkml.kernel.org/r/20170619235447.273417334@linutronix.de
-rw-r--r--include/linux/cpuhotplug.h1
-rw-r--r--include/linux/irq.h5
-rw-r--r--kernel/cpu.c5
-rw-r--r--kernel/irq/cpuhotplug.c45
4 files changed, 56 insertions, 0 deletions
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 0f2a80377520..c15f22c54535 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -124,6 +124,7 @@ enum cpuhp_state {
CPUHP_AP_ONLINE_IDLE,
CPUHP_AP_SMPBOOT_THREADS,
CPUHP_AP_X86_VDSO_VMA_ONLINE,
+ CPUHP_AP_IRQ_AFFINITY_ONLINE,
CPUHP_AP_PERF_ONLINE,
CPUHP_AP_PERF_X86_ONLINE,
CPUHP_AP_PERF_X86_UNCORE_ONLINE,
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 807042b46af1..19cea6326599 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -500,7 +500,12 @@ extern int irq_set_affinity_locked(struct irq_data *data,
const struct cpumask *cpumask, bool force);
extern int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info);
+#if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_IRQ_MIGRATION)
extern void irq_migrate_all_off_this_cpu(void);
+extern int irq_affinity_online_cpu(unsigned int cpu);
+#else
+# define irq_affinity_online_cpu NULL
+#endif
#if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_PENDING_IRQ)
void irq_move_irq(struct irq_data *data);
diff --git a/kernel/cpu.c b/kernel/cpu.c
index cb5103413bd8..b86b32ebb3b2 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1252,6 +1252,11 @@ static struct cpuhp_step cpuhp_ap_states[] = {
.startup.single = smpboot_unpark_threads,
.teardown.single = NULL,
},
+ [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
+ .name = "irq/affinity:online",
+ .startup.single = irq_affinity_online_cpu,
+ .teardown.single = NULL,
+ },
[CPUHP_AP_PERF_ONLINE] = {
.name = "perf:online",
.startup.single = perf_event_init_cpu,
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 0b093db3336b..b7964e72ded7 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -83,6 +83,15 @@ static bool migrate_one_irq(struct irq_desc *desc)
chip->irq_mask(d);
if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
+ /*
+ * If the interrupt is managed, then shut it down and leave
+ * the affinity untouched.
+ */
+ if (irqd_affinity_is_managed(d)) {
+ irqd_set_managed_shutdown(d);
+ irq_shutdown(desc);
+ return false;
+ }
affinity = cpu_online_mask;
brokeaff = true;
}
@@ -129,3 +138,39 @@ void irq_migrate_all_off_this_cpu(void)
}
}
}
+
+static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned int cpu)
+{
+ struct irq_data *data = irq_desc_get_irq_data(desc);
+ const struct cpumask *affinity = irq_data_get_affinity_mask(data);
+
+ if (!irqd_affinity_is_managed(data) || !desc->action ||
+ !irq_data_get_irq_chip(data) || !cpumask_test_cpu(cpu, affinity))
+ return;
+
+ if (irqd_is_managed_and_shutdown(data))
+ irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
+ else
+ irq_set_affinity_locked(data, affinity, false);
+}
+
+/**
+ * irq_affinity_online_cpu - Restore affinity for managed interrupts
+ * @cpu: Upcoming CPU for which interrupts should be restored
+ */
+int irq_affinity_online_cpu(unsigned int cpu)
+{
+ struct irq_desc *desc;
+ unsigned int irq;
+
+ irq_lock_sparse();
+ for_each_active_irq(irq) {
+ desc = irq_to_desc(irq);
+ raw_spin_lock_irq(&desc->lock);
+ irq_restore_affinity_of_irq(desc, cpu);
+ raw_spin_unlock_irq(&desc->lock);
+ }
+ irq_unlock_sparse();
+
+ return 0;
+}