linux-kernel - Re: [PATCH 3/3] ring-buffer: make cpu buffer entries counter atomic

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Message-Id: <20090430200607.9fc386ae.akpm@linux-foundation.org>
Date:	Thu, 30 Apr 2009 20:06:07 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 3/3] ring-buffer: make cpu buffer entries counter atomic

On Thu, 30 Apr 2009 22:22:13 -0400 Steven Rostedt <rostedt@...dmis.org> wrote:

> @@ -405,7 +405,7 @@ struct ring_buffer_per_cpu {
>  	unsigned long			nmi_dropped;
>  	unsigned long			commit_overrun;
>  	unsigned long			overrun;
> -	unsigned long			entries;
> +	atomic_t			entries;

This switches `entries' from unsigned-64-bit to signed-32-bit.

The signedness thing is just an unfortunate thing with atomic_t and probably
doesn't matter.

The change in size might or might not be a bug - that's for the person
who didn't document the data structure to work out ;)




/*
 * head_page == tail_page && head == tail then buffer is empty.
 */
struct ring_buffer_per_cpu {

the comment refers to vaporfields?
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