Date: Tue, 11 Sep 2007 19:22:19 +0100
From: Arjan van de Ven <arjan@infradead.org>
To: Matti Linnanvuori <mattilinnanvuori@yahoo.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Do not deprecate binary semaphore or do allow mutex in software
 interrupt contexts
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On Tue, 11 Sep 2007 09:20:23 -0700 (PDT)
Matti Linnanvuori <mattilinnanvuori@yahoo.com> wrote:

>  Arjan van de Ven:
> > what do you do if the trylock fails?
> 
> Just do not read the status variable now but modify the timer to run
> later.
> 
> > to be honest, the scenario describe really smells of broken
> > locking, in fact it really sounds like it wants to use spinlocks
> > instead 
> 
> No, I don't think it is broken.
> Spinlocks can be used, but I don't see them being obviously better in
> all cases. If access takes a long time, it is better to sleep during
> it. And if you sleep, you might just end up creating a new mutex
> implementation with a spinlock.


at this point the discussion has gone so theoretical that I think it's
better to go with a real example. What actual source code do you think
is a legit case for this?

I still think that whatever case you have in mind is better served with
something else, but until we see the actual complete drier we're both
talking air.
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