linux-kernel - [tip:x86/urgent] x86, cpu hotplug: Fix stack frame warning in check_irq_vectors_for_cpu

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Date:	Thu, 30 Jan 2014 16:42:39 -0800
From:	tip-bot for Prarit Bhargava <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	mingo@...nel.org, seiji.aguchi@....com, tony.luck@...el.com,
	gong.chen@...ux.intel.com, ruiv.wang@...il.com,
	janet.morgan@...el.com, ak@...ux.intel.com, tglx@...utronix.de,
	fengguang.wu@...el.com, rientjes@...gle.com, hpa@...or.com,
	linux-kernel@...r.kernel.org, yinghai@...nel.org,
	yang.z.zhang@...el.com, hpa@...ux.intel.com, prarit@...hat.com,
	walken@...gle.com, paul.gortmaker@...driver.com
Subject: [tip:x86/urgent] x86, cpu hotplug:
  Fix stack frame warning in check_irq_vectors_for_cpu_disable()

Commit-ID:  39424e89d64661faa0a2e00c5ad1e6dbeebfa972
Gitweb:     http://git.kernel.org/tip/39424e89d64661faa0a2e00c5ad1e6dbeebfa972
Author:     Prarit Bhargava <prarit@...hat.com>
AuthorDate: Tue, 28 Jan 2014 08:22:11 -0500
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Thu, 30 Jan 2014 16:40:13 -0800

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 <fengguang.wu@...el.com>
Tested-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Link: http://lkml.kernel.org/r/1390915331-27375-1-git-send-email-prarit@redhat.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: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.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 dbb6087..d99f31d 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);
--
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