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    SubjectRe: [PATCH] proc/softirqs: only show state for online cpus
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    On Wed, Jul 27, 2011 at 12:34 AM, Heiko Carstens
    <heiko.carstens@de.ibm.com> wrote:
    > On Tue, Jul 26, 2011 at 03:29:43PM +0800, Yong Zhang wrote:
    >> > Offtopic, /proc/interrupt should be protected by get_online_cpus().
    >> > Otherwise the header (i.e. cpu number) and the actual statistics fields
    >> > can be mismatched likes following. Am I missing something?
    >>
    >> I think you are right. The reader could be preempted by cpu hotplug.
    >>
    >> After searching the whole tree, only s390 take cpu_hotplug.lock,
    >> but its usage is not currect:
    >>
    >> arch/s390/kernel/irq.c:
    >> int show_interrupts(struct seq_file *p, void *v)
    >> {
    >>           get_online_cpus();
    >>           .........
    >>           put_online_cpus();
    >> }
    >>
    >> Because the reader will call show_interrupts nr_irqs times.
    >> So get_online_cpus()/put_online_cpus() should be put upper,
    >> maybe interrupts_open(). How do you think about it?
    >
    > Indeed, it's broken. You're going to submit a patch?
    >

    Yeah, coming soon :)

    Thanks,
    Yong



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