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Date: Mon, 17 Feb 2003 09:31:38 -0500 (EST)
From: Zwane Mwaikambo <zwane@holomorphy.com>
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To: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
cc: Richard Henderson <rth@twiddle.net>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH][2.5] Protect smp_call_function_data w/ spinlocks on
 Alpha
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On Mon, 17 Feb 2003, Ivan Kokshaysky wrote:

> On Mon, Feb 17, 2003 at 03:32:09AM -0500, Zwane Mwaikambo wrote:
> > Assigns whatever the pointer happens to be at the time, be it NULL or the 
> > next incoming message call.
> 
> No, the pointer is guaranteed to be valid.
> 
> > Therefore we'd need a lock to protect both the variable and critical 
> > section.
> 
> But smp_call_function_data pointer itself is exactly such a lock -
> other CPUs can't enter the section between 'if (pointer_lock())' and
> 'smp_call_function_data = 0', so there is no need for extra lock
> variable. Additionally, pointer_lock() with retry = 0 acts as spin_trylock.

Oh my mistake i thought you were talking about atomic assignment and not 
blocking at that point. I misunderstood what you stated.

	Zwane
-- 
function.linuxpower.ca
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