Messages in this thread | | | Date | Sun, 21 Dec 2008 12:55:39 +0100 | From | Jan Niehusmann <> | Subject | Re: KVM guest lockup |
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On Fri, Dec 19, 2008 at 06:44:01PM +0100, Max Kellermann wrote: > By starting kvm with "-s", I was able to attach gdb to KVM. The > following backtrace is with default options: > > #0 0xffffffff8023f3e0 in update_wall_time () at kernel/time/timekeeping.c:515 [...]
> The next one is with "noapic nolapic acpi=off": > > #0 0xffffffff8023f35a in update_wall_time () at kernel/time/timekeeping.c:501 > Both backtraces are from vanilla 2.6.28-rc8, .config attached. [...]
Looking at the code, both these lines of code are inside a loop which may run for quite a while if clocksource_read(clock) returns non-monotonic values:
offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask; [...] while (offset >= clock->cycle_interval) { /* accumulate one interval */ offset -= clock->cycle_interval; [...] }
As I observed such behaviour only when the host has frequency scaling activated: Could it be that in this case, clocksource_read(clock) on the guest is misbehaving?
Jan
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