On 11/21/2017 09:35 AM, Christian Borntraeger wrote: > > > On 11/20/2017 09:52 PM, Jens Axboe wrote: >> On 11/20/2017 01:49 PM, Christian Borntraeger wrote: >>> >>> >>> On 11/20/2017 08:42 PM, Jens Axboe wrote: >>>> On 11/20/2017 12:29 PM, Christian Borntraeger wrote: >>>>> >>>>> >>>>> On 11/20/2017 08:20 PM, Bart Van Assche wrote: >>>>>> On Fri, 2017-11-17 at 15:42 +0100, Christian Borntraeger wrote: >>>>>>> This is >>>>>>> >>>>>>> b7a71e66d (Jens Axboe 2017-08-01 09:28:24 -0600 1141) >>>>>>> * are mapped to it. >>>>>>> b7a71e66d (Jens Axboe 2017-08-01 09:28:24 -0600 1142) >>>>>>> */ >>>>>>> 6a83e74d2 (Bart Van Assche 2016-11-02 10:09:51 -0600 1143) >>>>>>> WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) && >>>>>>> 6a83e74d2 (Bart Van Assche 2016-11-02 10:09:51 -0600 1144) >>>>>>> cpu_online(hctx->next_cpu)); >>>>>>> 6a83e74d2 (Bart Van Assche 2016-11-02 10:09:51 -0600 1145) >>>>>>> b7a71e66d (Jens Axboe 2017-08-01 09:28:24 -0600 1146) >>>>>>> /* >>>>>> >>>>>> Did you really try to figure out when the code that reported the warning >>>>>> was introduced? I think that warning was introduced through the following >>>>>> commit: >>>>> >>>>> This was more a cut'n'paste to show which warning triggered since line >>>>> numbers are somewhat volatile. >>>>> >>>>>> >>>>>> commit fd1270d5df6a005e1248e87042159a799cc4b2c9 >>>>>> Date: Wed Apr 16 09:23:48 2014 -0600 >>>>>> >>>>>> blk-mq: don't use preempt_count() to check for right CPU >>>>>> >>>>>> UP or CONFIG_PREEMPT_NONE will return 0, and what we really >>>>>> want to check is whether or not we are on the right CPU. >>>>>> So don't make PREEMPT part of this, just test the CPU in >>>>>> the mask directly. >>>>>> >>>>>> Anyway, I think that warning is appropriate and useful. So the next step >>>>>> is to figure out what work item was involved and why that work item got >>>>>> executed on the wrong CPU. >>>>> >>>>> It seems to be related to virtio-blk (is triggered by fio on such disks). >>>>> Your comment basically >>>>> says: "no this is not a known issue" then :-) >>>>> I will try to take a dump to find out the work item >>>> >>>> blk-mq does not attempt to freeze/sync existing work if a CPU goes away, >>>> and we reconfigure the mappings. So I don't think the above is unexpected, >>>> if you are doing CPU hot unplug while running a fio job. >>> >>> I did a cpu hot plug (adding a CPU) and I started fio AFTER that. >> >> OK, that's different, we should not be triggering a warning for that. >> What does your machine/virtblk topology look like in terms of CPUS, >> nr of queues for virtblk, etc? > > FWIW, 4.11 does work, 4.12 and later is broken.
In fact: 4.12 is fine, 4.12.14 is broken.
