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    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@redhat.com>
    AuthorDate: Tue, 28 Jan 2014 08:22:11 -0500
    Committer: H. Peter Anvin <hpa@linux.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@intel.com>
    Tested-by: David Rientjes <rientjes@google.com>
    Signed-off-by: Prarit Bhargava <prarit@redhat.com>
    Link: http://lkml.kernel.org/r/1390915331-27375-1-git-send-email-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: Yinghai Lu <yinghai@kernel.org>
    Signed-off-by: H. Peter Anvin <hpa@linux.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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