Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architectureindependent macro

From: Stephen Boyd
Date: Wed Jul 31 2013 - 21:36:21 EST

On 07/31/13 17:20, Timur Tabi wrote:
> On 07/31/2013 07:16 PM, Stephen Boyd wrote:
>> cpu_relax() is usually just a compiler barrier or an instruction hint to
>> the cpu that it should cool down because we're spinning in a tight loop.
>> It certainly shouldn't be calling into the scheduler.
> Ah yes, I remember now. So it does seem that if we can fix the problem
> of non-incrementing 'jiffies', then this macro can be used in interrupts.

That's encouraging. It looks like you introduced it to use in interrupt
context but then it got shot down[1]? I lost track in all the versions.

> Of course, that assumes that spinning in interrupt context is a good
> idea to begin with. Maybe we shouldn't be encouraging it?

I read through the v5 discussion and it seems I'm about to walk through
some tall grass on the way to Cerulean City.

Andrew Morton, I choose you! Use your mind-power move to convince
everyone that having a macro for spinning on a register in interrupt
context is a good thing. At least it will be more obvious.

>>>> FYI, you might want to look at the code reviews for spin_event_timeout()
>>>> on the linuxppc-dev mailing list, back in March 2009.
>> Sure. Any pointers? Otherwise I'll go digging around the archives.


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