x86, cpu hotplug: Fix stack frame warning in check_irq_vectors_for_cpu_disable()

Further discussion here: http://marc.info/?l=linux-kernel&m=139073901101034&w=2

kbuild, 0day kernel build service, outputs the warning:

arch/x86/kernel/irq.c:333:1: warning: the frame size of 2056 bytes
is larger than 2048 bytes [-Wframe-larger-than=]

because check_irq_vectors_for_cpu_disable() allocates two cpumasks on the
stack.   Fix this by moving the two cpumasks to a global file context.

Reported-by: Fengguang Wu <[email protected]>
Tested-by: David Rientjes <[email protected]>
Signed-off-by: Prarit Bhargava <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Cc: Andi Kleen <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Seiji Aguchi <[email protected]>
Cc: Yang Zhang <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Janet Morgan <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Ruiv Wang <[email protected]>
Cc: Gong Chen <[email protected]>
Cc: Yinghai Lu <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>

1 files changed, 8 insertions, 1 deletions

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index dbb60878b744..d99f31d9a750 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -266,6 +266,14 @@ __visible void smp_trace_x86_platform_ipi(struct pt_regs *regs)
 EXPORT_SYMBOL_GPL(vector_used_by_percpu_irq);
 
 #ifdef CONFIG_HOTPLUG_CPU
+
+/* These two declarations are only used in check_irq_vectors_for_cpu_disable()
+ * below, which is protected by stop_machine().  Putting them on the stack
+ * results in a stack frame overflow.  Dynamically allocating could result in a
+ * failure so declare these two cpumasks as global.
+ */
+static struct cpumask affinity_new, online_new;
+
 /*
  * This cpu is going to be removed and its vectors migrated to the remaining
  * online cpus.  Check to see if there are enough vectors in the remaining cpus.
@@ -277,7 +285,6 @@ int check_irq_vectors_for_cpu_disable(void)
 	unsigned int this_cpu, vector, this_count, count;
 	struct irq_desc *desc;
 	struct irq_data *data;
-	struct cpumask affinity_new, online_new;
 
 	this_cpu = smp_processor_id();
 	cpumask_copy(&online_new, cpu_online_mask);