Re: [RFC PATCH 5/8] irq_work: Make self-IPIs optable

Frederic Weisbecker
2012-10-23T12:34:23Z

2012/10/22 Peter Zijlstra <peterz@infradead.org>:
> On Sat, 2012-10-20 at 12:22 -0400, Frederic Weisbecker wrote:
>> + if (empty) {
>> + /*
>> + * If an IPI is requested, raise it right away. Otherwise wait
>> + * for the next tick unless it's stopped. Now if the arch uses
>> + * some other obscure way than IPI to raise an irq work, just raise
>> + * and don't think further.
>> + */
>> + if (ipi || !arch_irq_work_has_ipi() || tick_nohz_tick_stopped())
>> + arch_irq_work_raise();
>> + }
>> preempt_enable();
>> }
>
> Doesn't this have a problem where we enqueue the first lazy and then one
> with ipi? In that case it appears we won't send the IPI because the
> queue wasn't empty.

Good point! I need to send an ipi in that case. Will fix on the next version.

Thanks.