Re: [PATCH] sound_core.c: Remove BKL from soundcore_open

[Arjan van de Ven <arjan@infradead.org>]

On Sun, 11 Oct 2009 20:17:59 +0100
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> > it's getting time though to bite the bullet and make it a real
> > normal mutex. Lockdep will then flag a bunch of sh*t we'll need to
> > fix, but without doing that we're never going to really make
> > progress. 
> 
> It won't. Instead you get situations like one ioctl blocking another
> to an unrelated device that just causes weird failures and performance
> problems, or in some cases deadlocks.

yes the bkl using code will be slower because it'll now hit contention.

The deadlocks we need to catch imo; those are the behaviors that are
the worst offenders in terms of BKL weird behavior.

> 
> Open routines block so it takes about 5 seconds of thought to realise
> that using a mutex here is brain dead and doesn't work.

it also takes 5 seconds to realize "uh oh. they block. BKL is rather
limited in what it provides".


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org