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Message-ID: <4A30793C.6090208@cn.fujitsu.com>
Date: Thu, 11 Jun 2009 11:25:48 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Steven Rostedt <rostedt@...dmis.org>
CC: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Theodore Tso <tytso@....edu>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Mathieu Desnoyers <compudj@...stal.dyndns.org>,
"Martin J. Bligh" <mbligh@...igh.org>,
Christoph Hellwig <hch@...radead.org>,
Li Zefan <lizf@...fujitsu.com>,
Huang Ying <ying.huang@...el.com>,
"H. Peter Anvin" <hpa@...or.com>,
Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
Masami Hiramatsu <mhiramat@...hat.com>,
Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 1/3] ring-buffer: make the buffer a true circular link
list
Steven Rostedt wrote:
> On Thu, 11 Jun 2009, Lai Jiangshan wrote:
>
>>> - list_splice(&pages, head);
>>> + /*
>>> + * The ring buffer page list is a circular list that does not
>>> + * start and end with a list head. All page list items point to
>>> + * other pages. Remove one of the pages, init its list head,
>>> + * and use list splice to move the rest of the pages to it.
>>> + */
>>> + bpage = list_entry(pages.next, struct buffer_page, list);
>>> + list_del_init(&bpage->list);
>>> + cpu_buffer->pages = &bpage->list;
>>> +
>>> + list_splice(&pages, cpu_buffer->pages);
>>> +
>> Is it proper?
>>
>> cpu_buffer->pages = pages.next;
>> list_del(&pages);
>>
>
> Not sure what you are asking here?
>
I'm not sure whether these 4 lines:
bpage = list_entry(pages.next, struct buffer_page, list);
list_del_init(&bpage->list);
cpu_buffer->pages = &bpage->list;
list_splice(&pages, cpu_buffer->pages);
equal to these 2 lines:
cpu_buffer->pages = pages.next;
list_del(&pages);
If there are equivalent, I think the second one
are simpler. It may be not a really necessarily cleanup.
What I asked is: if there are equivalent, could you use these two line:
cpu_buffer->pages = pages.next;
list_del(&pages);
Lai.
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