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SubjectRe: [PATCH] Option to disable AMD C1E (allows dynticks to work)
Thanks for the detailed response.

I thought I had gotten to the bottom of my problems when I found that
udev workaround, I guess I was naive.

I did the two tests you described and they predictably caused the hard
hangs. I needed to run the port80 program only once to get the hard

The output of the dmidecode commands were :


I applied the patch you provided ( luckily I am using 2.6.24-rc6-git3
kernel because I need the b43 driver ), added these values and compiled.

.callback = dmi_io_delay_port_alt,
.ident = "Compaq Presario v6000",
.matches = {

I was able to boot without the udev workaround and can now use hwclock
without hanging the system. In dmesg I can see this new line :

On Sat, 2007-12-29 at 09:43 -0500, David P. Reed wrote:
> Islam Amer wrote:
> > Hello.
> > I was interested in getting dynticks to work on my compaq presario v6000
> > to help with the 1 hour thirty minutes battery time, but after this
> > discussion I lost interest.
> >
> > I too had the early boot time hang, and found it was udev triggering the
> > bug.
> >
> This early boot time hang is *almost certainly* due to the in/out port
> 80 bug, which I discovered a few weeks ago, which affects hwclock and
> other I/O device drivers on a number of HP/Compaq machines in exactly
> this way. The proper fix for this bug is in dispute, and will probably
> not occur in the 2.6.24 release because it touches code in many, many
> drivers. The simplest way to test if you have a problem of this sort is
> to try this shell line as root, after you boot successfully. If your
> machine hangs hard, you have a problem that really looks like the port
> 80 problem.
> for ((i = 0; i < 1000; i = i + 1)); do cat /dev/nvram > /dev/null; done
> I have also attached a c program that only touches port 80. Compile it
> for 32-bit mode (see comment), run it as root, and after two or three
> runs, it will hang a system that has the port 80 bug.
> If you then run:
> dmidecode -s baseboard-manufacturer
> dmidecode -s baseboard-product-name
> are the values you should plug into the .matches field in the
> dmi_system_id struct in the attached patch. It would be great if you
> could do that, test, and post back with those values so they can be
> accumulated. HP/Compaq machines with quanta m/b's are very popular, and
> very common - so at least a quirk patch for all the broken models would
> be worth doing in 2.6.25 or downstream in the distros. The right
> patches will probably take a long time - there is a dispute as to what
> the semantics of port 80 writes even mean among the core kernel
> developers, because the hack is lost in the dim dark days of history,
> and safe resolution will take time
> There is also a C1E issue with the BIOS in my machine (an HP Pavilion
> dv9000z). I don't know if it is a bug, yet, but that's a different
> problem - associated with dynticks, perhaps. I have to say that
> researching the AMD Kernel/BIOS docs on C1E (a very new feature in the
> last year on AMD) leaves me puzzled as to whether the dynticks problem
> exists on my machine at all, but the patch for it turns off dynticks!
> > Changing the /etc/init.d/udev script so that the line containing
> >
> > /sbin/udevtrigger
> >
> > to
> >
> > /sbin/udevtrigger --subsystem-nomatch="*misc*"
> >
> > seemed to fix things.
> >
> > the hang is triggered specifically by
> >
> > echo add > /sys/class/misc/rtc/uevent
> > after inserting rtc.ko
> >
> > Also using hwclock to set the rtc , will cause a hard hang, if you are
> > using 64bit linux. Disable the init scripts that set the time, or use
> > the 32bit binary, as suggested here :
> >
> >
> >
> > I hope this helps. But your hardware is slightly different though.
> >

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