On Fri, Mar 30, 2007 at 10:38:01AM -0700, Pete Zaitcev wrote:
> On Fri, 30 Mar 2007 11:17:28 +0200, Oliver Neukum <[EMAIL PROTECTED]> wrote:
> 
> > This can'be solved with a simple spinlock, as wait_event() can sleep.
> 
> That's because wait_event() and its ilk make a bad API. I mentioned it
> many times before, and the answer by its pushers was "make the condition
> to be a function call and take locks inside it". That's just dumb,
> because it works around the silly design. The correct answer is not
> to use wait_event ever.

Agreed.

> > Really somebody went to some effort to find a lockless solution and
> > did well, he just didn't figure out of order execution units. You'd destroy
> > that.
> 
> That somebody obviously needs a girlfriend. Lockless execution in a
> printer driver, that's awesome.
> 
> The bottom line is, there's no excuse for using any kind of smp_mb()
> in USB drivers. None at all. When we have 100Gbit/s USB, then perhaps
> we can talk about it.

Perhaps then, but even then, I doubt it...

I really don't want the "normal" driver developer to have to worry about
things like smp_mb() in their code.  We have a hard enough time dealing
with other, more basic race condition issues :)

thanks,

greg k-h

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