linux-kernel - Re: [PATCH 3/5] ring-buffer: read page interface

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Message-Id: <200812030939.29907.rusty@rustcorp.com.au>
Date:	Wed, 3 Dec 2008 09:39:29 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, fweisbec@...il.com, srostedt@...hat.com
Subject: Re: [PATCH 3/5] ring-buffer: read page interface

On Wednesday 03 December 2008 08:06:54 Andrew Morton wrote:
> Steven Rostedt <rostedt@...dmis.org> wrote:
> > +	if (!local_read(&cpu_buffer->reader_page->page->commit))
>
> Rusty (I think it was Rusty) has convincingly argued that local_t is
> irredeemably busted.  I forget the details?

That was probably Christoph Lameter.  The x86 implementation needs some love, 
but the API seems reasonable.

On x86-32, the cpu_local_inc should be (as intended) turned into one insn.  
That would be possible on 64 bit once we get zero-based percpu (as will World 
Peace).

Cheers,
Rusty.
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