Re: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8

[Ingo Molnar]

* Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> > > This is used to wait for command completion and therefor we have the
> > > completion API. It was used this way because the ancestor of completion
> > > (sleep_on) was racy !
> > 
> > I didn't look at the USB code, I'm just saying that it's perfectly valid
> > use of a semaphore the pattern you describe (process A holding it,
> > process B releasing it).
> 
> Yeah, for a semaphore it is, but not for a mutex.

but mutexes dont exist in upstream Linux as a separate entity. (they
exist in my tree but that's another ballgame.)

> IMHO, this is not clearly seperated and therefor produces a lot of
> confusion.

if used to complete some work then semaphores are indeed a tad unclean
and slightly slower than completions - but they are fully correct kernel
code. And there are much worse offenders of cleanliness around.

	Ingo
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