Re: [PATCH -V2] acpi: don't cond_resched if irq is disabled

[Alexey Starikovskiy]

Pavel Machek ÐÐÑÐÑ:
> On Fri 2009-12-11 14:48:21, Alexey Starikovskiy wrote:
>   
>> Lin Ming ??????????:
>>     
>>> On Thu, 2009-12-10 at 20:21 +0800, Alexey Starikovskiy wrote:
>>>       
>>>> Hi Xiaotian,
>>>>
>>>> I think, this is another round of "armor vs. bullet" race... It will hold until
>>>> might_sleep() logic changes again.
>>>>
>>>> Please consider using preemptible() -- IMHO this is the check we should perform 
>>>> in our case of voluntary preemption.
>>>>         
>>> preemptible() may not work here because it always returns 0 for
>>> non-preemptible kernel.
>>>       
>> Right, and it means that this machine does not care about low latency that much.
>> The reason we introduced the preemption point in the first place, was unacceptable latency
>> due to very long AML methods on some machines. We don't need this preemption point for normal
>> operation, this is exactly what voluntary preemption does -- allows those in hurry to pass by.
>> If there are none, fine.
>>     
>>> #ifdef CONFIG_PREEMPT
>>> # define preemptible()  (preempt_count() == 0 && !irqs_disabled())
>>> # define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
>>> #else
>>> # define preemptible()  0
>>> # define IRQ_EXIT_OFFSET HARDIRQ_OFFSET
>>> #endif
>>>       
>
> Well, normally we want low latency even for !CONFIG_PREEMPT kernels.
>
> Actually, explicit preemption points are NOPs for CONFIG_PREEMPT
> kernels, right?
> 									Pavel
>   
Right. Do you have code?

Thanks,
Alex.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/