genirq/cpuhotplug: Reorder check logic

Move the checks for a valid irq chip and the irq_set_affinity() callback
right in front of the whole migration logic. No point in doing a gazillion
of other things when the interrupt cannot be migrated at all.

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/20170619235445.354181630@linutronix.de

diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 9c5521b247d56fc38641b6562dcf7c2d5c1fccaf..41fe1e04d5d9dc838e25eafc8fa0f44fa0b5d46a 100644 (file)
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -17,9 +17,20 @@
 static bool migrate_one_irq(struct irq_desc *desc)
 {
        struct irq_data *d = irq_desc_get_irq_data(desc);
+       struct irq_chip *chip = irq_data_get_irq_chip(d);
        const struct cpumask *affinity = d->common->affinity;
-       struct irq_chip *c;
-       bool ret = false;
+       bool brokeaff = false;
+       int err;
+
+       /*
+        * IRQ chip might be already torn down, but the irq descriptor is
+        * still in the radix tree. Also if the chip has no affinity setter,
+        * nothing can be done here.
+        */
+       if (!chip || !chip->irq_set_affinity) {
+               pr_debug("IRQ %u: Unable to migrate away\n", d->irq);
+               return false;
+       }
 
        /*
         * If this is a per-CPU interrupt, or the affinity does not
@@ -31,23 +42,16 @@ static bool migrate_one_irq(struct irq_desc *desc)
 
        if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
                affinity = cpu_online_mask;
-               ret = true;
+               brokeaff = true;
        }
 
-       c = irq_data_get_irq_chip(d);
-       if (!c->irq_set_affinity) {
-               pr_debug("IRQ%u: unable to set affinity\n", d->irq);
-               ret = false;
-       } else {
-               int r = irq_do_set_affinity(d, affinity, false);
-               if (r) {
-                       pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n",
-                                           d->irq, r);
-                       ret = false;
-               }
+       err = irq_do_set_affinity(d, affinity, false);
+       if (err) {
+               pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n",
+                                   d->irq, err);
+               return false;
        }
-
-       return ret;
+       return brokeaff;
 }
 
 /**