[Xen-devel] PowerNow BUG with Xen

["Niraj Tolia" <ntolia@xxxxxxxxx>]

I installed Xen 3.2.0 on an AMD Dual-Core AMD Opteron (Processor 2216 HE) and am trying to experiment with frequency scaling. This machine has two sockets (4 cores). The powernow_k8 module is being used and cpufreq=dom0-kernel was passed on the Xen command line. Apart from the "Time went backwards" messages that have been discussed recently on the list, I get the following BUG messages whenever I run cpufreq-info. Note that the "time went backwards" messages shown below are also correlated with executing cpufreq-info. Apart from that, the system _seems_ to be switching frequencies just fine.

Anything to be concerned about? I can debug this more if needed.

Thanks,
Niraj

Feb  2 19:34:59 bladespp-c4 kernel: BUG: warning at/home/ntolia/src/linux-2.6.18-xen.hg/arch/i386/kernel/time-xen.c:1136/time_cpufreq_notifier()
Feb  2 19:34:59 bladespp-c4 kernel:  [time_cpufreq_notifier+146/160] time_cpufreq_notifier+0x92/0xa0
Feb  2 19:34:59 bladespp-c4 kernel:  [do_softirq+121/128] do_softirq+0x79/0x80
Feb  2 19:34:59 bladespp-c4 kernel:  [do_IRQ+68/160] do_IRQ+0x44/0xa0
Feb  2 19:34:59 bladespp-c4 kernel:  [do_softirq+121/128] do_softirq+0x79/0x80
Feb  2 19:34:59 bladespp-c4 kernel:  [evtchn_do_upcall+199/480] evtchn_do_upcall+0xc7/0x1e0
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_stats_update+39/112] cpufreq_stats_update+0x27/0x70
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_stat_notifier_trans+114/144] cpufreq_stat_notifier_trans+0x72/0x90
Feb  2 19:34:59 bladespp-c4 kernel:  [notifier_call_chain+37/48] notifier_call_chain+0x25/0x30
Feb  2 19:34:59 bladespp-c4 kernel:  [blocking_notifier_call_chain+37/64] blocking_notifier_call_chain+0x25/0x40
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_notify_transition+120/176] cpufreq_notify_transition+0x78/0xb0
Feb  2 19:34:59 bladespp-c4 kernel:  [<ee7e2a6f>] powernowk8_target+0x27f/0x650 [powernow_k8]
Feb  2 19:34:59 bladespp-c4 kernel:  [sys_sched_yield+80/144] sys_sched_yield+0x50/0x90
Feb  2 19:34:59 bladespp-c4 kernel:  [<ee7e27f0>] powernowk8_target+0x0/0x650 [powernow_k8]
Feb  2 19:34:59 bladespp-c4 kernel:  [__cpufreq_driver_target+60/64] __cpufreq_driver_target+0x3c/0x40
Feb  2 19:34:59 bladespp-c4 kernel:  [<ee7d717a>] cpufreq_governor_userspace+0x16a/0x180 [cpufreq_userspace]
Feb  2 19:34:59 bladespp-c4 kernel:  [__cpufreq_governor+70/224] __cpufreq_governor+0x46/0xe0
Feb  2 19:34:59 bladespp-c4 kernel:  [__cpufreq_set_policy+244/304] __cpufreq_set_policy+0xf4/0x130
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_update_policy+169/240] cpufreq_update_policy+0xa9/0xf0
Feb  2 19:34:59 bladespp-c4 kernel:  [handle_update+0/16] handle_update+0x0/0x10
Feb  2 19:34:59 bladespp-c4 kernel:  [run_workqueue+114/240] run_workqueue+0x72/0xf0
Feb  2 19:34:59 bladespp-c4 kernel:  [handle_update+0/16] handle_update+0x0/0x10
Feb  2 19:34:59 bladespp-c4 kernel:  [worker_thread+284/320] worker_thread+0x11c/0x140
Feb  2 19:34:59 bladespp-c4 kernel:  [default_wake_function+0/16] default_wake_function+0x0/0x10
Feb  2 19:34:59 bladespp-c4 kernel:  [worker_thread+0/320] worker_thread+0x0/0x140
Feb  2 19:34:59 bladespp-c4 kernel:  [kthread+246/256] kthread+0xf6/0x100
Feb  2 19:34:59 bladespp-c4 kernel:  [kthread+0/256] kthread+0x0/0x100
Feb  2 19:34:59 bladespp-c4 kernel:  [kernel_thread_helper+5/16] kernel_thread_helper+0x5/0x10
Feb  2 19:34:59 bladespp-c4 kernel: BUG: warning at /home/ntolia/src/linux-2.6.18-xen.hg/arch/i386/kernel/time-xen.c:1136/time_cpufreq_notifier()
Feb  2 19:34:59 bladespp-c4 kernel:  [time_cpufreq_notifier+146/160] time_cpufreq_notifier+0x92/0xa0
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_stats_update+39/112] cpufreq_stats_update+0x27/0x70
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_stat_notifier_trans+114/144] cpufreq_stat_notifier_trans+0x72/0x90
Feb  2 19:34:59 bladespp-c4 kernel:  [notifier_call_chain+37/48] notifier_call_chain+0x25/0x30
Feb  2 19:34:59 bladespp-c4 kernel:  [blocking_notifier_call_chain+37/64] blocking_notifier_call_chain+0x25/0x40
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_notify_transition+120/176] cpufreq_notify_transition+0x78/0xb0
Feb  2 19:34:59 bladespp-c4 kernel:  [<ee7e2a6f>] powernowk8_target+0x27f/0x650 [powernow_k8]
Feb  2 19:34:59 bladespp-c4 kernel:  [show_total_trans+16/64] show_total_trans+0x10/0x40
Feb  2 19:34:59 bladespp-c4 kernel:  [<ee7e27f0>] powernowk8_target+0x0/0x650 [powernow_k8]
Feb  2 19:34:59 bladespp-c4 kernel:  [__cpufreq_driver_target+60/64] __cpufreq_driver_target+0x3c/0x40
Feb  2 19:34:59 bladespp-c4 kernel:  [<ee149758>] cpufreq_governor_dbs+0x248/0x310 [cpufreq_ondemand]
Feb  2 19:34:59 bladespp-c4 kernel:  [notifier_call_chain+37/48] notifier_call_chain+0x25/0x30
Feb  2 19:34:59 bladespp-c4 kernel:  [__cpufreq_governor+70/224] __cpufreq_governor+0x46/0xe0
Feb  2 19:34:59 bladespp-c4 kernel:  [__cpufreq_set_policy+244/304] __cpufreq_set_policy+0xf4/0x130
Feb  2 19:34:59 bladespp-c4 kernel:  [cpufreq_update_policy+169/240] cpufreq_update_policy+0xa9/0xf0
Feb  2 19:34:59 bladespp-c4 kernel:  [handle_update+0/16] handle_update+0x0/0x10
Feb  2 19:34:59 bladespp-c4 kernel:  [run_workqueue+114/240] run_workqueue+0x72/0xf0
Feb  2 19:34:59 bladespp-c4 kernel:  [handle_update+0/16] handle_update+0x0/0x10
Feb  2 19:34:59 bladespp-c4 kernel:  [worker_thread+284/320] worker_thread+0x11c/0x140
Feb  2 19:34:59 bladespp-c4 kernel:  [default_wake_function+0/16] default_wake_function+0x0/0x10
Feb  2 19:34:59 bladespp-c4 kernel:  [worker_thread+0/320] worker_thread+0x0/0x140
Feb  2 19:34:59 bladespp-c4 kernel:  [kthread+246/256] kthread+0xf6/0x100
Feb  2 19:34:59 bladespp-c4 kernel:  [kthread+0/256] kthread+0x0/0x100
Feb  2 19:34:59 bladespp-c4 kernel:  [kernel_thread_helper+5/16] kernel_thread_helper+0x5/0x10
Feb  2 19:35:00 bladespp-c4 kernel: Timer ISR/2: Time went backwards: delta=-709993774 delta_cpu=39979827 shadow=475167307195 off=742699969 processed=476620000000 cpu_processed=475870026399
Feb  2 19:35:00 bladespp-c4 kernel:  0: 475870000000
Feb  2 19:35:00 bladespp-c4 kernel:  1: 476600026399
Feb  2 19:35:00 bladespp-c4 kernel:  2: 475870026399
Feb  2 19:35:00 bladespp-c4 kernel:  3: 476610026399
Feb  2 19:35:01 bladespp-c4 kernel: Timer ISR/0: Time went backwards: delta=-1212398058 delta_cpu=97601942 shadow=475365708622 off=601893837 processed=477180000000 cpu_processed=475870000000
Feb  2 19:35:01 bladespp-c4 kernel:  0: 475870000000
Feb  2 19:35:01 bladespp-c4 kernel:  1: 477160026399
Feb  2 19:35:01 bladespp-c4 kernel:  2: 477170026399
Feb  2 19:35:01 bladespp-c4 kernel:  3: 477170026399
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