Re: [Xen-devel] [PATCH v3 18/18] xen/arm: IRQ: Handle multiple action per IRQ

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.04.14 at 18:17, <Ian.Campbell@xxxxxxxxxx> wrote:
> On Wed, 2014-04-16 at 17:06 +0100, Julien Grall wrote:
>> On 04/16/2014 04:54 PM, Ian Campbell wrote:
>> > On Tue, 2014-04-08 at 15:44 +0100, Julien Grall wrote:
>> >>          desc->status &= ~IRQ_PENDING;
>> >>          spin_unlock_irq(&desc->lock);
>> >> -        action->handler(irq, action->dev_id, regs);
>> >> +        list_for_each_entry_safe(action, next, &desc->action, next)
>> >> +            action->handler(irq, action->dev_id, regs);
>> > 
>> > You aren't removing entries from within the loop so I don't think you
>> > need the _safe variant.
>> 
>> As we release the desc->lock here, it might be possible to have the list
>> changed under the CPU feet by release_irq.
>> 
>> With the double-linked list, how do we make sure that it won't happen?
> 
> Normally by using a lock. I don't know if even list_for_each_entry_safe
> is safe against concurrent changes to the list from other threads, I
> think it only refers to safe to changing the list within the loop in
> this thread.

Indeed.

Jan


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