genirq: Provide irq_fixup_move_pending()

If an CPU goes offline, the interrupts are migrated away, but a eventually
pending interrupt move, which has not yet been made effective is kept
pending even if the outgoing CPU is the sole target of the pending affinity
mask. What's worse is, that the pending affinity mask is discarded even if
it would contain a valid subset of the online CPUs.

Implement a helper function which allows to avoid these issues.

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/20170619235444.691345468@linutronix.de

1 files changed, 30 insertions, 0 deletions

diff --git a/kernel/irq/migration.c b/kernel/irq/migration.c
index 37ddb7b..6ca054a 100644
--- a/kernel/irq/migration.c
+++ b/kernel/irq/migration.c
@@ -4,6 +4,36 @@
 
 #include "internals.h"
 
+/**
+ * irq_fixup_move_pending - Cleanup irq move pending from a dying CPU
+ * @desc:		Interrupt descpriptor to clean up
+ * @force_clear:	If set clear the move pending bit unconditionally.
+ *			If not set, clear it only when the dying CPU is the
+ *			last one in the pending mask.
+ *
+ * Returns true if the pending bit was set and the pending mask contains an
+ * online CPU other than the dying CPU.
+ */
+bool irq_fixup_move_pending(struct irq_desc *desc, bool force_clear)
+{
+	struct irq_data *data = irq_desc_get_irq_data(desc);
+
+	if (!irqd_is_setaffinity_pending(data))
+		return false;
+
+	/*
+	 * The outgoing CPU might be the last online target in a pending
+	 * interrupt move. If that's the case clear the pending move bit.
+	 */
+	if (cpumask_any_and(desc->pending_mask, cpu_online_mask) >= nr_cpu_ids) {
+		irqd_clr_move_pending(data);
+		return false;
+	}
+	if (force_clear)
+		irqd_clr_move_pending(data);
+	return true;
+}
+
 void irq_move_masked_irq(struct irq_data *idata)
 {
 	struct irq_desc *desc = irq_data_to_desc(idata);