Messages in this thread | | | Date | Wed, 31 Jul 2013 17:16:49 -0700 | From | Stephen Boyd <> | Subject | Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro |
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On 07/31/13 17:13, Timur Tabi wrote: > On 07/31/2013 07:04 PM, Stephen Boyd wrote: >> If it yields why are we using udelay? Why not usleep_range()? It would >> be useful to have a variant that worked in interrupt context and it >> looked like that was almost possible. > I've never heard of usleep_range() before, so I don't know if it > applies. Apparently, udelay() includes its own call to cpu_relax(). Is > it possible that cpu_relax() is a "lightweight" yield, compared to sleeping?
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.
> > 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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