On 11/21/2017 01:19 PM, Christian Borntraeger wrote: > > On 11/21/2017 09:14 PM, Jens Axboe wrote: >> On 11/21/2017 01:12 PM, Christian Borntraeger wrote: >>> >>> >>> On 11/21/2017 08:30 PM, Jens Axboe wrote: >>>> On 11/21/2017 12:15 PM, Christian Borntraeger wrote: >>>>> >>>>> >>>>> On 11/21/2017 07:39 PM, Jens Axboe wrote: >>>>>> On 11/21/2017 11:27 AM, Jens Axboe wrote: >>>>>>> On 11/21/2017 11:12 AM, Christian Borntraeger wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 11/21/2017 07:09 PM, Jens Axboe wrote: >>>>>>>>> On 11/21/2017 10:27 AM, Jens Axboe wrote: >>>>>>>>>> On 11/21/2017 03:14 AM, Christian Borntraeger wrote: >>>>>>>>>>> Bisect points to >>>>>>>>>>> >>>>>>>>>>> 1b5a7455d345b223d3a4658a9e5fce985b7998c1 is the first bad commit >>>>>>>>>>> commit 1b5a7455d345b223d3a4658a9e5fce985b7998c1 >>>>>>>>>>> Author: Christoph Hellwig <hch@xxxxxx> >>>>>>>>>>> Date: Mon Jun 26 12:20:57 2017 +0200 >>>>>>>>>>> >>>>>>>>>>> blk-mq: Create hctx for each present CPU >>>>>>>>>>> >>>>>>>>>>> commit 4b855ad37194f7bdbb200ce7a1c7051fecb56a08 upstream. >>>>>>>>>>> >>>>>>>>>>> Currently we only create hctx for online CPUs, which can lead to a lot >>>>>>>>>>> of churn due to frequent soft offline / online operations. Instead >>>>>>>>>>> allocate one for each present CPU to avoid this and dramatically simplify >>>>>>>>>>> the code. >>>>>>>>>>> >>>>>>>>>>> Signed-off-by: Christoph Hellwig <hch@xxxxxx> >>>>>>>>>>> Reviewed-by: Jens Axboe <axboe@xxxxxxxxx> >>>>>>>>>>> Cc: Keith Busch <keith.busch@xxxxxxxxx> >>>>>>>>>>> Cc: linux-block@xxxxxxxxxxxxxxx >>>>>>>>>>> Cc: linux-nvme@xxxxxxxxxxxxxxxxxxx >>>>>>>>>>> Link: http://lkml.kernel.org/r/20170626102058.10200-3-hch@xxxxxx >>>>>>>>>>> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >>>>>>>>>>> Cc: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx> >>>>>>>>>>> Cc: Mike Galbraith <efault@xxxxxx> >>>>>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> >>>>>>>>>> >>>>>>>>>> I wonder if we're simply not getting the masks updated correctly. I'll >>>>>>>>>> take a look. >>>>>>>>> >>>>>>>>> Can't make it trigger here. We do init for each present CPU, which means >>>>>>>>> that if I offline a few CPUs here and register a queue, those still show >>>>>>>>> up as present (just offline) and get mapped accordingly. >>>>>>>>> >>>>>>>>> From the looks of it, your setup is different. If the CPU doesn't show >>>>>>>>> up as present and it gets hotplugged, then I can see how this condition >>>>>>>>> would trigger. What environment are you running this in? We might have >>>>>>>>> to re-introduce the cpu hotplug notifier, right now we just monitor >>>>>>>>> for a dead cpu and handle that. >>>>>>>> >>>>>>>> I am not doing a hot unplug and the replug, I use KVM and add a previously >>>>>>>> not available CPU. >>>>>>>> >>>>>>>> in libvirt/virsh speak: >>>>>>>> <vcpu placement='static' current='1'>4</vcpu> >>>>>>> >>>>>>> So that's why we run into problems. It's not present when we load the device, >>>>>>> but becomes present and online afterwards. >>>>>>> >>>>>>> Christoph, we used to handle this just fine, your patch broke it. >>>>>>> >>>>>>> I'll see if I can come up with an appropriate fix. >>>>>> >>>>>> Can you try the below? >>>>> >>>>> >>>>> It does prevent the crash but it seems that the new CPU is not "used " after the hotplug for mq: >>>>> >>>>> >>>>> output with 2 cpus: >>>>> /sys/kernel/debug/block/vda >>>>> /sys/kernel/debug/block/vda/hctx0 >>>>> /sys/kernel/debug/block/vda/hctx0/cpu0 >>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/completed >>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/merged >>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/dispatched >>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/rq_list >>>>> /sys/kernel/debug/block/vda/hctx0/active >>>>> /sys/kernel/debug/block/vda/hctx0/run >>>>> /sys/kernel/debug/block/vda/hctx0/queued >>>>> /sys/kernel/debug/block/vda/hctx0/dispatched >>>>> /sys/kernel/debug/block/vda/hctx0/io_poll >>>>> /sys/kernel/debug/block/vda/hctx0/sched_tags_bitmap >>>>> /sys/kernel/debug/block/vda/hctx0/sched_tags >>>>> /sys/kernel/debug/block/vda/hctx0/tags_bitmap >>>>> /sys/kernel/debug/block/vda/hctx0/tags >>>>> /sys/kernel/debug/block/vda/hctx0/ctx_map >>>>> /sys/kernel/debug/block/vda/hctx0/busy >>>>> /sys/kernel/debug/block/vda/hctx0/dispatch >>>>> /sys/kernel/debug/block/vda/hctx0/flags >>>>> /sys/kernel/debug/block/vda/hctx0/state >>>>> /sys/kernel/debug/block/vda/sched >>>>> /sys/kernel/debug/block/vda/sched/dispatch >>>>> /sys/kernel/debug/block/vda/sched/starved >>>>> /sys/kernel/debug/block/vda/sched/batching >>>>> /sys/kernel/debug/block/vda/sched/write_next_rq >>>>> /sys/kernel/debug/block/vda/sched/write_fifo_list >>>>> /sys/kernel/debug/block/vda/sched/read_next_rq >>>>> /sys/kernel/debug/block/vda/sched/read_fifo_list >>>>> /sys/kernel/debug/block/vda/write_hints >>>>> /sys/kernel/debug/block/vda/state >>>>> /sys/kernel/debug/block/vda/requeue_list >>>>> /sys/kernel/debug/block/vda/poll_stat >>>> >>>> Try this, basically just a revert. >>> >>> Yes, seems to work. >>> >>> Tested-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> >> >> Great, thanks for testing. >> >>> Do you know why the original commit made it into 4.12 stable? After all >>> it has no Fixes tag and no cc stable- >> >> I was wondering the same thing when you said it was in 4.12.stable and >> not in 4.12 release. That patch should absolutely not have gone into >> stable, it's not marked as such and it's not fixing a problem that is >> stable worthy. In fact, it's causing a regression... >> >> Greg? Upstream commit is mentioned higher up, start of the email. >> > > > Forgot to cc Greg? I did, thanks for doing that. Now I wonder how to mark this patch, as we should revert it from kernels that have the bad commit. 4.12 is fine, 4.12.later-stable is not. -- Jens Axboe