linux-kernel - Re: [PATCH v3 3/4] mm: cma: add list of currently allocated CMA buffers to debugfs

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Message-ID: <xa1tk2yz2ksr.fsf@mina86.com>
Date:	Mon, 02 Mar 2015 21:42:28 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Stefan Strogin <s.strogin@...tner.samsung.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	aneesh.kumar@...ux.vnet.ibm.com,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Dmitry Safonov <d.safonov@...tner.samsung.com>,
	Pintu Kumar <pintu.k@...sung.com>,
	Weijie Yang <weijie.yang@...sung.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	SeongJae Park <sj38.park@...il.com>,
	Hui Zhu <zhuhui@...omi.com>, Minchan Kim <minchan@...nel.org>,
	Dyasly Sergey <s.dyasly@...sung.com>,
	Vyacheslav Tyrtov <v.tyrtov@...sung.com>,
	Aleksei Mateosian <a.mateosian@...sung.com>,
	gregory.0xf0@...il.com, sasha.levin@...cle.com, gioh.kim@....com,
	pavel@....cz, stefan.strogin@...il.com
Subject: Re: [PATCH v3 3/4] mm: cma: add list of currently allocated CMA buffers to debugfs

On Mon, Mar 02 2015, Stefan Strogin <s.strogin@...tner.samsung.com> wrote:
> My fault. You are right.
> I'm not sure how to do the output nice... I could use *ppos to point the
> number of next list entry to read (like that is used in
> read_page_owner()). But in this case the list could be changed before we
> finish reading, it's bad.
> Or we could use seq_files like in v1, iterating over buffer_list
> entries. But seq_print_stack_trace() has to be added.

I’m not that familiar with seq_* so my opinion may be ill-informed, but
I feel that skipping some entries while (de)allocations happen is akin
to process reading a file while some other process modifies it.  This is
a debug function so perhaps it’s acceptable that it may return garbage
if not used carefully?

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--
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