Re: HPET regression in 2.6.26 versus 2.6.25 -- RCU problem
Thanks for the reply. Let me address these out of order (cutting
> David, it would be nice to check whether tip/master still locks up for
> just to make sure no pending fix resolves your issue. (the bug is
> probably still present, but might be worth checking nevertheless.)[/color]
Just to recap (not sure if you saw the earlier posts in the thread, going
back to Monday a week ago):
- kernel 2.6.25 worked for me without error
- kernel 2.6.26 locked up at boot when it finally became availble in
- I was asked to grab Linus' git tree and try that, last Tuesday --
v2.6.27-rc1 locked up like the 2.6.26 kernels.
OK, now grabbing "tip":
===== BEGIN SHELL STUFF =========
$ git remote add tip git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git
$ git remote update
$ git checkout tip/master
$ git show
Merge: 2097987... 2ae111c...
Author: Ingo Molnar <email@example.com>
Date: Mon Aug 11 16:43:42 2008 +0200
Merge branch 'x86/core'
===== END SHELL STUFF =========
I copied into .config the configuration that I had prepared for 2.6.26
(which was prepared from my most recent version for 2.6.25) and ran
'make oldconfig'. The kernel built fine, so I installed it and rebooted.
The kernel locked up as expected at inet_init(). Rebooting, and adding
"hpet=disable", allowed it to boot just fine... as expected.
I understand the need to do this, and was hoping that it would just
magically start working again. But it didn't ... which means I don't
have to bisect again to find out when, where, and why! ;)
> You can probably verify this by adding something like this to
> kernel/timer.c's do_timer() function:
> if (printk_ratelimit())
> printk("timer irq hit, jiffies: %ld\n", jiffies);[/color]
So I made this change to do_timer(), and rebuilt the kernel.
Unfortunately, I cannot report whether this change made a difference
in the output. This is a 2.5 GHz AMD X2 4850e processor, and in the
few moments before freeze (maybe < 2 secs) the lines just scroll too
fast for me to read them. Once the kernel locks up, that's it... no
I can report that the do_timer() change worked correctly, though. I
rebooted with "hpet=disabled", and just happened to hit an automatic
fsck on a 460 GB partition. The printk()'s interfere with the fsck
progress indicator: about every 4 secs, ten of those printk()'s fire
off very quickly. (Pretty annoying, actually.)
> Yinghai, do you have any ideas about this particular problem? One theory
> would be that your e820 changes might have caused a shuffling of
> resources that made the hpet's timer IRQ generation inoperable.[/color]
It's so weird that this commit works on so many machines, but fails on
the 2 machines I have (with the same motherboard). Of course, many
more people/machines might be affected by this issue, but they simply
aren't using 2.6.26 yet... and will find out later, the hard way!
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