linux-kernel - Re: [PATCH] net: wireless: airo semaphore to mutex

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Message-Id: <200805271437.23114.rusty@rustcorp.com.au>
Date:	Tue, 27 May 2008 14:37:22 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Michal Schmidt <mschmidt@...hat.com>,
	Daniel Walker <dwalker@...sta.com>, linville@...driver.com,
	mingo@...e.hu, linux-kernel@...r.kernel.org,
	linux-wireless@...r.kernel.org, arjan@...radead.org
Subject: Re: [PATCH] net: wireless: airo semaphore to mutex

On Tuesday 27 May 2008 12:15:03 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.

Shows how little I know, I didn't see priority boosting in my glance thru 
mutex.c.

But it seems like mutex_trylock_irq would be easy to add if needed, if only 
for clarity.

Thanks!
Rusty.
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