[tip:sched/core] sched/core: Add debugging code to catch missing update_rq_clock() calls

[Matt Fleming]

On Tue, 31 Jan, at 08:24:53AM, Michael Ellerman wrote:
> 
> I'm hitting this on multiple powerpc systems:
> 
> [   38.339126] rq->clock_update_flags < RQCF_ACT_SKIP
> [   38.339134] ------------[ cut here ]------------
> [   38.339142] WARNING: CPU: 2 PID: 1 at kernel/sched/sched.h:804 detach_task_cfs_rq+0xa0c/0xd10

[...]
 
> I assume I should be worried?

Thanks for the report. No need to worry, the bug has existed for a
while, this patch just turns on the warning ;-)

The following commit queued up in tip/sched/core should fix your
issues (assuming you see the same callstack on all your powerpc
machines):

  https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=sched/core&id=1b1d62254df0fe42a711eb71948f915918987790