linux-kernel - Re: [PATCH 8/8] x86: I/O APIC: Timer through 8259A second-chance

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Message-ID: <Pine.LNX.4.55.0806051911500.2875@cliff.in.clinika.pl>
Date:	Thu, 5 Jun 2008 19:33:04 +0100 (BST)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH 8/8] x86: I/O APIC: Timer through 8259A second-chance

On Thu, 5 Jun 2008, Ingo Molnar wrote:

> NOTE: you need to copy out and use the boot parameters from the boot 
> log:
> 
>  [ 0.000000] Command line: root=/dev/sda6 console=ttyS0,115200 
>  earlyprintk=se rial,ttyS0,115200 debug initcall_debug apic=verbose 
>  sysrq_always_enabled ignore _loglevel selinux=0 nmi_watchdog=1 
>  profile=0 maxcpus=1 nosmp no_hz=off highres =0 noapic nolapic_timer 
>  hpet=disable idle=mwait
> 
> as -tip testing occasionally randomizes boot parameters too. (to find 
> regressions like this) Let me know if you cannot reproduce this.

 Thanks.  I figured out I cannot build an x86-64 kernel, because my i386
compiler does not support the target.  Probably because of target library
dependencies at the time I built my compiler.  I would have to build a
bare-iron cross-compiler for the x86-64 which I'd rather not to just to
fix this small problem -- it usually takes a few days to sort out all the
pesky details when doing such a build from scratch, so it better be well
justified.

 However, the reason is quite clear to me -- the command line specifies
"noapic" among others (there is also "nosmp", but probably overridden by
"maxcpus=1" -- I am afraid there is no clear precedence among these
options), so the bug is the I/O APIC NMI watchdog is tried at all.  This
is also clearly seen from the log where the I/O APIC is not set up at all.  

 A fix along the lines of what I implemented for "nosmp" in the
"nosmp-watchdog" patch is needed which I will post shortly.  It's needed
both for the i386 and the x86-64 target; hopefully the latter does not
differ too much from the former.

  Maciej
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