Messages in this thread | | | From | Bjørn Mork <> | Subject | Re: [v3.10-rc1] WARNING: at kernel/rcutree.c:502 | Date | Tue, 14 May 2013 09:38:56 +0200 |
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"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> writes: > On 05/13/2013 08:09 PM, Bjørn Mork wrote: > >> Hey, hey, hey. Turns out this wasn't that wrong after all. That merge >> includes a oneline diff in kernel/cpu/idle.c and it *is* actually this >> diff which trigger the problem for me. Reverting it, using the attached >> patch, makes the warning go away. Which means that it had nothing to do >> with your RCU changes. >> >> But I haven't the faintest idea how this is supposed to work, or even >> how to explain the patch properly, so I think I need some help from >> Thomas here. Unless this makes you understand the real issue? >> >> Thomas, why does powertop trigger the >> >> WARNING: at kernel/rcutree.c:502 rcu_eqs_exit_common.isra.48+0x3d/0x125() >> >> without the attached patch? And what is the proper resolution? >> > > 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:
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().
> 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. I assume this is the correct fix even if the problem isn't completely understood?
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