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Subject[PATCH] x86, cpu hotplug, Fix stack frame warning in check_irq_vectors_for_cpu_disable()
Date
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.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Yang Zhang <yang.z.zhang@Intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Janet Morgan <janet.morgan@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Ruiv Wang <ruiv.wang@gmail.com>
Cc: Gong Chen <gong.chen@linux.intel.com>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Gong Chen <gong.chen@linux.intel.com>
Cc: x86@kernel.org
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: yinghai@kernel.org
Cc: tglx@linutronix.de
Cc: mingo@elte.hu
Cc: hpa@zytor.com
---
arch/x86/kernel/irq.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 4207e8d..3910078 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -262,6 +262,14 @@ __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.
@@ -273,7 +281,6 @@ 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);
--
1.7.9.3


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