linux-kernel - Re: linux-next requirements

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Message-ID: <20100227093948.GB31794@elte.hu>
Date:	Sat, 27 Feb 2010 10:39:48 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Stephen Rothwell <sfr@...b.auug.org.au>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	roland@...hat.com, suresh.b.siddha@...el.com, tglx@...utronix.de,
	hjl.tools@...il.com, Andrew Morton <akpm@...ux-foundation.org>,
	Linus <torvalds@...ux-foundation.org>
Subject: Re: linux-next requirements

* Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> [I have removed linux-tip-commits from the cc list]
> 
> Hi Ingo,
> 
> On Tue, 23 Feb 2010 09:45:52 +0100 Ingo Molnar <mingo@...e.hu> wrote:
> >
> > Developers simply cannot be expected to build for 22 architectures, and 
> > they shouldnt be.
> 
> I have agreed with this point of yours several times.  Why do you keep 
> stating it?

If you agree with me then why do you put so much focus on cross-arch build 
failures, versus other, more relevant forms of testing?

> > The thing is, last i checked you didnt even _test_ x86 as the first step 
> > in your linux-next build tests. Most of your generic build bug reports are 
> > against PowerPC. They create the appearance that x86 is a second class 
> > citizen in linux-next.
> 
> Lets see.  Over the last 60 days, I have reported 37 build errors.  Of 
> these, 16 were reported against x86, 14 against ppc, 7 against other archs.

So only 43% of them were even relevant on the platform that 95+% of the Linux 
testers use? Seems to support the points i made.

> Of the ppc reports, 10 would not affect x86 builds (due to being ppc 
> specific problems or dependencies on implicit includes that do happen on 
> x86).  None of the reports against other arches would affect x86 builds.
> 
> I also reported 31 warnings.  15 against x86, 15 against ppc and 1 against 
> both.  Of those only reported against ppc, 13 did not affect x86.
> 
> So of my "generic" reports, 4 errors and 2 warnings were reported against 
> ppc, 16 errors and 15 warnings again x86.
> 
> Also, I am not sure how reports of 37 build errors and 32 warnings over 60 
> days can tax the resources of our developer base. [...]

Note that out of those 37 build errors only a small minority were caused by 
any tree i co-maintain. (i dont have the precise numbers but it's below 5)

Why? Because i cross-build before pushing to linux-next. I bug people about 
cross-arch build failures, and about the patch flow delays and hickups this 
causes. Without that you'd see twice that many cross-build failures.

Which in itself is not bad of course (any fix is a good fix) - except the 
forced prioritization and its place in the workflow: it sends the wrong 
testing message.

It sends the message that building on N architectures is more important than 
for the code to work for real people. I've had good developers waste their 
time trying to set up cross-build testing environments and complain to me how 
this complicates their testing.

> [...]  Most of these are fairly trivial to fix (as is shown by how quick 
> they are fixed.  Usually the developer has just forgotten to test the 
> !CONFIG_SOMETHING case or used some function without explicitly including 
> the file that declares it.
> 
> As to my perceived pro-PowerPC and anti-x86 bias, you are the only one who 
> has even mentioned it to me.

Have you asked me recently for example?

> Anyway, I sick of these discussions.  If people see the way I do linux-next 
> as a problem, then they can find someone else.  That is not the impression I 
> gained at the Kernel Summit and (apart from these occasional "discussions") 
> I am quite happy to continue.

Not sure how you jump from my observations to "I will quit if you do this". I 
am simply pointing out problems as i see them - as i do that with every piece 
of the workflow we use. I have expressed my views numerous times about where i 
find linux-next useful and positive - and it's sure a net positive.

	Ingo
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