linux-kernel - Re: [PATCH] mm: clear pages_scanned only if draining a pcp adds pages to the buddy allocator again

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Message-ID: <CAHGf_=rQ6AaZBjfvkWWKi+a5q+1R29_PGWDyD77VFisgJHPQEA@mail.gmail.com>
Date:	Fri, 22 Jun 2012 17:10:59 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mel@....ul.ie>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH] mm: clear pages_scanned only if draining a pcp adds pages
 to the buddy allocator again

On Fri, Jun 22, 2012 at 4:19 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 14 Jun 2012 12:16:10 -0400
> kosaki.motohiro@...il.com wrote:
>
>> commit 2ff754fa8f (mm: clear pages_scanned only if draining a pcp adds pages
>> to the buddy allocator again) fixed one free_pcppages_bulk() misuse. But two
>> another miuse still exist.
>
> This changelog is irritating.  One can understand it a bit if one
> happens to have a git repo handy (and why do this to the reader?), but
> the changelog for 2ff754fa8f indicates that the patch might fix a
> livelock.  Is that true of this patch?  Who knows...

The code in this simple patch speak the right usage, isn't it? And yes,
this patch also fixes a possibility of live lock. (but i haven't seen actual
live lock cause from this mistake)

When anyone find a function misuse and fixes it, He/She should confirm other
callsite and should all of mistake too. Otherwise we observe the same issue
sooner of later.
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