[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [question] what's the purpose of smp_send_event_check_mask?
On Thu, Jan 19, 2012 at 5:14 PM, Keir Fraser <keir.xen@xxxxxxxxx> wrote: > > On 19/01/2012 09:02, "Kai Huang" <mail.kai.huang@xxxxxxxxx> wrote: > >> Hi, >> >> I see cpu_raise_softirq calls smp_send_event_check_mask after setting >> softirq bit for target CPU if target CPU is not the current CPU. I >> thought smp_send_event_check_mask will send IPI to target CPU and then >> trigger target CPU to run pending irq, but seems >> smp_send_event_check_mask does nothing but jast ACK the IPI. So what's >> the purpose of this function? Why do we need this function? > > Xen always checks softirqs on return from interrupt context to guest > context, and also in its idle loopon wakeup. Hence the event_check interrupt > handler itself doesn't need to do anything. Does this mean if raising softirq for remote CPU, we don't need to call do_softirq explicitly on target CPU? -cody > >> BTW, would someone gives me some knowledge when will the pending irqs >> be triggered to run after setting up the pending bits? Seems normally >> they are called asynchronously. > > Yes, of course it's asynchronous, the smp_send_event_check_mask interrupt is > just to make sure it happens "soon". > > -- Keir > >> Thanks in advance! >> >> -cody >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@xxxxxxxxxxxxxxxxxxx >> http://lists.xensource.com/xen-devel > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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