genirq: Prevent irq storm on migration

move_native_irq() masks and unmasks the interrupt line
unconditionally, but the interrupt line might be masked due to a
threaded oneshot handler in progress. Unmasking the line in that case
can lead to interrupt storms. Observed on PREEMPT_RT.

Originally-from: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org

1 files changed, 11 insertions, 3 deletions

diff --git a/kernel/irq/migration.c b/kernel/irq/migration.c
index 1d2541940480..441fd629ff04 100644
--- a/kernel/irq/migration.c
+++ b/kernel/irq/migration.c
@@ -56,6 +56,7 @@ void move_masked_irq(int irq)
 void move_native_irq(int irq)
 {
         struct irq_desc *desc = irq_to_desc(irq);
+        bool masked;
 
         if (likely(!(desc->status & IRQ_MOVE_PENDING)))
                 return;
@@ -63,8 +64,15 @@ void move_native_irq(int irq)
         if (unlikely(desc->status & IRQ_DISABLED))
                 return;
 
-        desc->irq_data.chip->irq_mask(&desc->irq_data);
+        /*
+         * Be careful vs. already masked interrupts. If this is a
+         * threaded interrupt with ONESHOT set, we can end up with an
+         * interrupt storm.
+         */
+        masked = desc->status & IRQ_MASKED;
+        if (!masked)
+                desc->irq_data.chip->irq_mask(&desc->irq_data);
         move_masked_irq(irq);
-        desc->irq_data.chip->irq_unmask(&desc->irq_data);
+        if (!masked)
+                desc->irq_data.chip->irq_unmask(&desc->irq_data);
 }
-