[Xen-devel] Time went backwards

[Rik van Riel <riel@xxxxxxxxxx>]

I am very frequently seeing these Time went backwards messages
on my test systems.  Running a 2 VCPU guest on a single CPU
computer seems to be effective at triggering this ;)

As you can see from the messages below, cpu_processed tends
to be one or two jiffies larger than processed, which equals
to "delta - cpu_delta".

I have been staring at timer_interrupt() for a few days now
and trying a few things, but the bug continues.  Note that
this problem starts very early at boot time, before the root
filesystem is mounted even...

Timer ISR/0: Time went backwards: delta=3962070 cpu_delta=-37930 
shadow=152513705782853 off=54253888 processed=152513756074150 
cpu_processed=152513760074150
 0: 152513760074150
 1: 152513420074150
Timer ISR/0: Time went backwards: delta=4009918 cpu_delta=-3990082 
shadow=152662706855499 off=369229091 processed=152663072074150 
cpu_processed=152663080074150
 0: 152663080074150
 1: 152663016074150
Timer ISR/0: Time went backwards: delta=3973296 cpu_delta=-26704 
shadow=152662706855499 off=373192366 processed=152663076074150 
cpu_processed=152663080074150
 0: 152663080074150
 1: 152663016074150
Timer ISR/0: Time went backwards: delta=2084348 cpu_delta=-1915652 
shadow=152662706855499 off=375303210 processed=152663080074150 
cpu_processed=152663084074150
 0: 152663084074150
 1: 152663016074150
Timer ISR/0: Time went backwards: delta=1932754 cpu_delta=-2067246 
shadow=152692707072523 off=234935002 processed=152692940074150 
cpu_processed=152692944074150
 0: 152692944074150
 1: 152692780074150


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