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Date: Wed, 19 Aug 2009 11:53:01 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, dhowells@redhat.com,
       Kumar Gala <galak@kernel.crashing.org>,
       Peter Zijlstra <peterz@infradead.org>,
       Linux-Kernel List <linux-kernel@vger.kernel.org>,
       Steven Rostedt <rostedt@goodmis.org>,
       linuxppc-dev list <linuxppc-dev@ozlabs.org>,
       Ingo Molnar <mingo@elte.hu>
Subject: Re: spin_is_locked() broken for uniprocessor?
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On Wed, 19 Aug 2009 10:38:06 +0100
David Howells <dhowells@redhat.com> wrote:

> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > > which implies to me that spin_is_locked() will always return false.  Is this
> > > expected behavior.
> > 
> > That's wrong. spin_is_locked should always return true on UP.
> 
> Surely it's not that simple?  Maybe spin_is_lock() should be undefined on UP.

That would lead to a lot of

#ifdef CONFIG_SMP

#endif

in drivers because there is driver code that uses spin_is_locked() in
fairly sensible fashion when dealing with locking.