Messages in this thread | | | From | Bjørn Mork <> | Subject | Re: [v3.10-rc1] WARNING: at kernel/rcutree.c:502 | Date | Tue, 14 May 2013 10:20:50 +0200 |
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"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> writes: > On 05/14/2013 01:08 PM, Bjørn Mork wrote: >> "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> writes: >> >>> The problem appears to be in the cpu idle poll implementation. You can trigger >>> this problem by passing idle=poll in the kernel cmd-line as well, right? >> >> That sounded so obvious that it made me think "Doh, why didn't I just >> test that before?" But unfortunately there must be some other factor >> involved. No warnings observed during normal use when running with >> idle=poll: >> > > I didn't expect warnings with normal use. > >> bjorn@nemi:~$ dmesg|grep polling >> [ 0.000000] process: using polling idle threads >> >> >> I expected a flood of warnings here, but there is none until I start >> powertop (to confirm that the original issue is still there). So it's >> more than just entering cpu_idle_poll(). >> > > Yeah, of course it is :-) The warning triggers only when you enable the tracepoint > in the idle code. And in your case, powertop does that. That's why it only > triggers when you run powertop. Alternatively, if you enable the tracepoint > yourself manually, I bet you'll see the warnings, even without using powertop.
Ah, right. That sounds so obvious I have to go "Doh!" again:)
>>> I think I understand what is going on here. Can you please try the fix below? >>> (It is only compile-tested since its very late here and I really need to get >>> some sleep!). >> >> Works perfect. Thanks. > > Thanks for your testing! > >> I assume this is the correct fix even if the >> problem isn't completely understood? >> > > Hmm? Why do you say the problem isn't completely understood? I thought I > explained the problem in my changelog. Did I miss something?
No, I did. I didn't understand the tracepoint part of this. But it is all perfectly clear to me too now, after your excellent explanation above.
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