Message-Id: <200711152239.14707.nickpiggin@yahoo.com.au>
Date:	Thu, 15 Nov 2007 22:39:14 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	David Miller <davem@...emloft.net>, mpm@...enic.com, rjw@...k.pl,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [bug] SLOB crash, 2.6.24-rc2

On Thursday 15 November 2007 22:28, Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@...oo.com.au> wrote:

> > Anyway, I'm really happy to see you're testing and using SLOB upstream
> >
> > :) Is there any particular reason that you're using it?
>
> i sometimes test SLOB for -rt, but this time it's the result of my
> "automated random QA" effort, as part of arch/x86 maintainance/QA.
>
> the main trick is to build and booting random "make randconfig"
> bzImages. That finds build bugs and a good deal of boot hang and crash
> bugs as well. (it also found a compiler bug already) I can build and
> boot about 1000 random kernels in 24 hours, and it's all fully
> automated. I usually run it overnight - when a kernel does not come up
> due to a bootup hang or crash (or the kernel log signals any exception
> condition) then the script stops and i can fix it in the morning.
>
> The first step towards this was to get allyesconfig bzImage kernels to
> build and boot fine. That effort took months (we had many problems in
> this area) - i think you saw bugreports and fixes from me about that on
> lkml.
>
> Once that worked reasonably well i made a small Kconfig patch that
> forcibly selects a "minimum set" of drivers and kernel subsystems that
> are needed to boot up a testsystem. Once a "make allnoconfig" and a
> "make allyesconfig" bzImage kernel boots up fine on the testbox all
> randconfig configs "inbetween" are supposed to build and boot fine as
> well.
>
> I also have a patch that adds all the x86 boot options like nosmp,
> maxcpus=1, nohz=off, hpet=disable to be selectable as .config options -
> so those boot options are randomized as well.
>
> I also have a small patch that disables half a dozen drivers/features
> that are not expected to work out of box in a bzImage kernel. (such as
> ISA drivers that assume the presence of hardware, or root filesystem
> features such as NFSROOT)
>
> the resulting make randconfig kernel still has 99% of the degrees of
> freedom that a stock make randconfig kernel has, so by all practical
> purposes it's a fully random kernel - it just happens to boot on my
> testsystem all the time.
>
> A successful bootup means the test system is able to boot up into a
> stock Fedora 8 userspace and is able to bring up its network interfaces
> and ssh out (automatically) to the build box to signal the completion of
> a successful test cycle. The logs are also analyzed for lockdep
> assertions (if lockdep is enabled - which it is in about 20% of the
> randconfig kernels) and other kernel bugs.
>
> (just in case you were wondering about one of the reasons why the
> arch/x86 unification merge went so smoothly, with nary a regression ;-)
> Thomas is doing other types of automated QA of the x86 queue as well.)

Well, my hat's off to you. Actually I was more wondering how it is
that you're catching SLOB bugs ;) so it seems your test setup is much
more useful than just to test the x86 arch code...
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