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SubjectRe: [rfc patch v2] rt,nohz_full: fix nohz_full for PREEMPT_RT_FULL
On 04/11/2015 03:36 PM, Mike Galbraith wrote:
> On Sat, 2015-04-11 at 15:15 +0200, Mike Galbraith wrote:
>>
>> @@ -117,10 +113,8 @@ bool irq_work_queue(struct irq_work *wor
>> if (work->flags & IRQ_WORK_HARD_IRQ) {
>> if (llist_add(&work->llnode,
>> this_cpu_ptr(&hirq_work_list)))
>> arch_irq_work_raise();
>> - } else {
>> - if (llist_add(&work->llnode,
>> this_cpu_ptr(&lazy_list)))
>> - arch_irq_work_raise();
>> - }
>> + } /* for lazy_list we have the timer irq */
>>
>> If we don't queue work without IRQ_WORK_HARD_IRQ set, how does it
>> run?
>>
>> Anyway, box did not livelock, nor did it with that bit reverted.
>
> Well, not reverted, I actually queued and maybe poked softirq, but
> didn't check whether anything was being queued or not, only caring for
> the nonce whether box went catatonic or kept on working.
>
> @@ -118,8 +115,9 @@ bool irq_work_queue(struct irq_work *wor
> if (llist_add(&work->llnode, this_cpu_ptr(&hirq_work_list)))
> arch_irq_work_raise();
> } else {
> - if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)))
> - arch_irq_work_raise();
> + if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
> + tick_nohz_tick_stopped())
> + raise_softirq(TIMER_SOFTIRQ);

This sounds like a good idea actually. Thanks.

Sebastian


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