genirq/affinity: Defer affinity setting if irq chip is busy

The case that interrupt affinity setting fails with -EBUSY can be handled in the kernel completely by using the already available generic pending infrastructure.

If a irq_chip::set_affinity() fails with -EBUSY, handle it like the interrupts for which irq_chip::set_affinity() can only be invoked from interrupt context. Copy the new affinity mask to irq_desc::pending_mask and set the affinity pending bit. The next raised interrupt for the affected irq will check the pending bit and try to set the new affinity from the handler. This avoids that -EBUSY is returned when an affinity change is requested from user space and the previous change has not been cleaned up. The new affinity will take effect when the next interrupt is raised from the device.

Fixes dccfe3147b42 ("x86/vector: Simplify vector move cleanup")

Signed-off-by Thomas Gleixner <[email protected]>

Cc [email protected]

---
 kernel/irq/manage.c |   37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

kernel/irq/manage.c +35 -2

@@ -204,6 +204,39 @@ int irq_do_set_affinity(struct irq_data
        return ret;
 }
 
+#ifdef CONFIG_GENERIC_PENDING_IRQ
+static inline int irq_set_affinity_pending(struct irq_data *data,
+                                          const struct cpumask *dest)
+{
+       struct irq_desc *desc = irq_data_to_desc(data);
+
+       irqd_set_move_pending(data);
+       irq_copy_pending(desc, dest);
+       return 0;
+}
+#else
+static inline int irq_set_affinity_pending(struct irq_data *data,
+                                          const struct cpumask *dest)
+{
+       return -EBUSY;
+}
+#endif
+
+static int irq_try_set_affinity(struct irq_data *data,
+                               const struct cpumask *dest, bool force)
+{
+       int ret = irq_do_set_affinity(data, dest, force);
+
+       /*
+        * In case that the underlying vector management is busy and the
+        * architecture supports the generic pending mechanism then utilize
+        * this to avoid returning an error to user space.
+        */
+       if (ret == -EBUSY && !force)
+               ret = irq_set_affinity_pending(data, dest);
+       return ret;
+}
+
 int irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask,
                            bool force)
 {

@@ -214,8 +247,8 @@ int irq_set_affinity_locked(struct irq_d
        if (!chip || !chip->irq_set_affinity)
                return -EINVAL;
 
-       if (irq_can_move_pcntxt(data)) {
-               ret = irq_do_set_affinity(data, mask, force);
+       if (irq_can_move_pcntxt(data) && !irqd_is_setaffinity_pending(data)) {
+               ret = irq_try_set_affinity(data, mask, force);
        } else {
                irqd_set_move_pending(data);
                irq_copy_pending(desc, mask);