linux-kernel - Re: [PATCH -v12 02/15] resources: Add probe

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Message-ID: <CA+55aFxLUExCZE1=gQpDT0ip9s+iMRYEVK2QjdCGNk9iympfYA@mail.gmail.com>
Date:	Tue, 28 Aug 2012 10:05:35 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Tony Luck <tony.luck@...el.com>,
	David Miller <davem@...emloft.net>, x86 <x86@...nel.org>,
	Dominik Brodowski <linux@...inikbrodowski.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH -v12 02/15] resources: Add probe_resource()

On Tue, Aug 28, 2012 at 9:09 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>
> please check update one. -v7

Ugh. Ok, looking closer at this, I think I agree with Bjorn. This is too ugly.

The whole "reduce size/needed_size by 1" double loop is O(n**2). And
it does ugly "insert fake resource to check, and then remove it". Ugh.

Maybe this works in practice for the special case of some PCI bus
numbers that are small integers, but the code is nasty nasty horrible
and not a generic resource allocation thing.

                Linus
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