Re: HPET timer broken using 2.6.23.13 / nanosleep() hangs

["Andrew Paprocki" <andrew@ishiboo.com>]

Thomas,

I haven't found a good way to capture the SysRq output for this. I
found that when it locks up at boot time, even SysRq is unresponsive.
I don't have another way of getting console on the machine right now
to get the output off of it. I have since upgraded to 2.6.24 and the
problem still persists.

Another interesting twist though.. I just rebuilt my kernel with
ARCH=x86_64 and HPET works perfectly. So this only appears to break
when in 32-bit mode. For some reason it picks tsc at boot time, but if
I install hpet afterwards under x86_64 it no longer hangs when I run
'sleep 1'. Does that shed any more light on the problem?

Thanks,
-Andrew

# uname -a
Linux am2 2.6.24 #7 Sat Feb 9 18:06:50 EST 2008 x86_64 GNU/Linux
# dmesg | egrep -i clock\|hpet
ACPI: HPET 3DFE7780, 0038 (r1 RS690  AWRDACPI 42302E31 AWRD       98)
ACPI: HPET id: 0x10b9a201 base: 0xfed00000
hpet clockevent registered
TSC calibrated against HPET
hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0
hpet0: 4 32-bit timers, 14318180 Hz
Time: tsc clocksource has been installed.
Real Time Clock Driver v1.12ac
hpet_resources: 0xfed00000 is busy
# echo -n hpet >
/sys/devices/system/clocksource/clocksource0/current_clocksource
# dmesg | tail -1
Time: hpet clocksource has been installed.
# time sleep 1

real    0m1.001s
user    0m0.000s
sys     0m0.000s

On Jan 18, 2008 5:26 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Wed, 16 Jan 2008, Andrew Paprocki wrote:
>
> > I applied the patch and I am still locking up after
> > Time: hpet clocksource has been installed.
>
> That was expected :)
>
> > I rebooted with "clocksource=tsc" to get the logs of the trace which
> > was added. I'm assuming the grep below gets all the interesting parts.
> > I enabled the HPET character device as mentioned before, which is why
> > the hpet0 lines appear now.
> >
> > # dmesg | egrep -i "(hpet|time|clock)"
> > ACPI: HPET 37FE7400, 0038 (r1 RS690  AWRDACPI 42302E31 AWRD       98)
> > ATI board detected. Disabling timer routing over 8254.
> > ACPI: PM-Timer IO Port: 0x4008
> > ACPI: HPET id: 0x10b9a201 base: 0xfed00000
> > Kernel command line: vga=0x31a root=/dev/sda1 ro clocksource=tsc
> > HPET check: t1=5 t2=1139 s=56226339975 n=56226539985
>
> Ok, the counter works when we initialize the HPET.
>
> t2-t1 = 1134 ticks ~= 79us
> s-n = 200010 ~= 2525MHz --> That should be the frequency of your CPU.
>
> > Jan 16 14:44:43 am2 kernel: Call Trace:
> > Jan 16 14:44:48 am2 kernel:  [<c01371be>] enqueue_hrtimer+0xd7/0xe2
> > Jan 16 14:44:48 am2 kernel:  [<c0137803>] hrtimer_start+0xe8/0xf4
> > Jan 16 14:44:48 am2 kernel:  [<c03ac8d3>] do_nanosleep+0x48/0x73
> > Jan 16 14:44:48 am2 kernel:  [<c03ac932>] hrtimer_nanosleep_restart+0x34/0xa1
> > Jan 16 14:44:48 am2 kernel:  [<c013735d>] hrtimer_wakeup+0x0/0x18
> > Jan 16 14:44:48 am2 kernel:  [<c012e837>] sys_restart_syscall+0xe/0xf
> > Jan 16 14:44:48 am2 kernel:  [<c0103d0a>] sysenter_past_esp+0x5f/0x85
>
> When the system is hung, can you please hit SysRq-Q wait a bit and hit
> SysRq-Q again. Please provide the output.
>
> Thanks,
>         tglx
>
>