linux-kernel - [PATCH] x86, cpu hotplug, Fix stack frame warning in check_irq_vectors_for_cpu

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Message-Id: <1390915331-27375-1-git-send-email-prarit@redhat.com>
Date:	Tue, 28 Jan 2014 08:22:11 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Prarit Bhargava <prarit@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Michel Lespinasse <walken@...gle.com>,
	Seiji Aguchi <seiji.aguchi@....com>,
	Yang Zhang <yang.z.zhang@...el.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Janet Morgan <janet.morgan@...el.com>,
	Tony Luck <tony.luck@...el.com>,
	Ruiv Wang <ruiv.wang@...il.com>,
	Gong Chen <gong.chen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>, x86@...nel.org,
	Fengguang Wu <fengguang.wu@...el.com>, yinghai@...nel.org,
	tglx@...utronix.de, mingo@...e.hu, hpa@...or.com
Subject: [PATCH] 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.

Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Michel Lespinasse <walken@...gle.com>
Cc: Seiji Aguchi <seiji.aguchi@....com>
Cc: Yang Zhang <yang.z.zhang@...el.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Janet Morgan <janet.morgan@...el.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Ruiv Wang <ruiv.wang@...il.com>
Cc: Gong Chen <gong.chen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...ux.intel.com>
Cc: Gong Chen <gong.chen@...ux.intel.com>
Cc: x86@...nel.org
Cc: Fengguang Wu <fengguang.wu@...el.com>
Cc: yinghai@...nel.org
Cc: tglx@...utronix.de
Cc: mingo@...e.hu
Cc: hpa@...or.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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