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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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