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Subject: Re: [PATCH] net: wireless: airo semaphore to mutex
From: Daniel Walker <dwalker@mvista.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
       Michal Schmidt <mschmidt@redhat.com>, linville@tuxdriver.com,
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Date: Mon, 26 May 2008 21:34:41 -0700
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On Mon, 2008-05-26 at 20:15 -0600, Matthew Wilcox wrote:
> On Tue, May 27, 2008 at 11:17:22AM +1000, Rusty Russell wrote:
> > On Tuesday 27 May 2008 03:29:14 Michal Schmidt wrote:
> > > Mutexes are not allowed in interrupt context, not even mutex_trylock.
> > 
> > As an aside, does anyone know why?  I know the documentation says so, but it 
> > wasn't immediately obvious to me.  I asked before to no response...
> 
> Because mutexes have an owner.  In interrupt context, there is no owner.
> This owner is used to do priority boosts as well as debugging.

I don't think regular mutexes do boosting, the rtmutex does tho .. I
think it's more a issue with lockdep complaining about the context, but
that exists to just plain disallow this type of usage on principal .

Daniel