Re: [PATCH]generic usb serial driver

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.

> 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.

-- Pete

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