[PATCH] kernel/irq: Limit validation of cpumask_var_t to CONFIG_CPUMASK_OFFSTACK=y

[Matthias Kaehlcke]

With CONFIG_CPUMASK_OFFSTACK=y cpumask_var_t is a struct cpumask
pointer, otherwise a struct cpumask array with a single element.

irq_thread_check_affinity() validates the cpumask_var_t field in the
interrupt descriptor by checking if it is not NULL. This works for
both CONFIG_CPUMASK_OFFSTACK=y/n, however clang raises the following
warning with CONFIG_CPUMASK_OFFSTACK=n:

kernel/irq/manage.c:839:28: error: address of array
'desc->irq_common_data.affinity' will always evaluate to 'true'
[-Werror,-Wpointer-bool-conversion]

To get rid of the warning only validate the cpumask_var_t field when
CONFIG_CPUMASK_OFFSTACK=y.

Signed-off-by: Matthias Kaehlcke <m...@chromium.org>
---
 kernel/irq/manage.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index a4afe5cc5af1..5d38fe85122b 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -848,14 +848,14 @@ irq_thread_check_affinity(struct irq_desc *desc, struct 
irqaction *action)
        }
 
        raw_spin_lock_irq(&desc->lock);
-       /*
-        * This code is triggered unconditionally. Check the affinity
-        * mask pointer. For CPU_MASK_OFFSTACK=n this is optimized out.
-        */
-       if (desc->irq_common_data.affinity)
-               cpumask_copy(mask, desc->irq_common_data.affinity);
-       else
+
+#ifdef CONFIG_CPUMASK_OFFSTACK
+       if (!desc->irq_common_data.affinity)
                valid = false;
+       else
+#endif
+       cpumask_copy(mask, desc->irq_common_data.affinity);
+
        raw_spin_unlock_irq(&desc->lock);
 
        if (valid)
-- 
2.12.2.715.g7642488e1d-goog