linux-kernel - Re: [PATCH 04/14] init: deps: order network interfaces by link order

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Date:	Sat, 17 Oct 2015 21:07:39 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russell King <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...aro.org>
Subject: Re: [PATCH 04/14] init: deps: order network interfaces by link order

Am 17.10.2015 um 21:03 schrieb Linus Torvalds:
> On Sat, Oct 17, 2015 at 11:37 AM, Alexander Holler <holler@...oftware.de> wrote:
>>
>> Otherwise it's impossible to call initcalls in parallel. I've seen a stable
>> topological sort somewhere, but whenever you want to parallelize the
>> initcalls, the stable ordering would be gone anyway. So I've decided not to
>> look further at a stable topological sort.
>
> So five seconds of googling gave me freely usable source code for a
> stable topological sort, that also has a nice reported added
> advantage:
>
>   "An interesting property of a stable topological sort is that cyclic
> dependencies are tolerated and resolved according to original order of
> elements in sequence. This is a desirable feature for many
> applications because it allows to sort any sequence with any
> imaginable dependencies between the elements"
>
> which seems to be *exactly* what you'd want, especially considering
> that right now your patches add extra "no-dependency" markers exactly
> because of the cyclical problem.

That's the stable topological sort I've mentioned the link to in the 
discussion with you.

>
> I think it was the #2 hit on google for "stable topological sort". I
> didn't look closely at the source code, but it was not big.
>
> And no, since we don't actually want to parallelize the initcalls
> anyway (I had this discussion with you just a month ago), your
> objections seem even more questionable. We have separate machinery for
> "do this asynchronously", and we want to _keep_ that separate.

I've understood that now.

Sorry for wasting your time.

Alexander Holler
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