Linux Virtualization - Nov 2017 - 4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable)

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 at
lst.de>
>>>>>>>>>> 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 at lst.de>
>>>>>>>>>>     Reviewed-by: Jens Axboe <axboe
at kernel.dk>
>>>>>>>>>>     Cc: Keith Busch <keith.busch at
intel.com>
>>>>>>>>>>     Cc: linux-block at vger.kernel.org
>>>>>>>>>>     Cc: linux-nvme at
lists.infradead.org
>>>>>>>>>>     Link:
http://lkml.kernel.org/r/20170626102058.10200-3-hch at lst.de
>>>>>>>>>>     Signed-off-by: Thomas Gleixner
<tglx at linutronix.de>
>>>>>>>>>>     Cc: Oleksandr Natalenko
<oleksandr at natalenko.name>
>>>>>>>>>>     Cc: Mike Galbraith <efault at
gmx.de>
>>>>>>>>>>     Signed-off-by: Greg Kroah-Hartman
<gregkh at linuxfoundation.org>
>>>>>>>>>
>>>>>>>>> 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 at de.ibm.com>
> 
> 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?

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
at lst.de>
>>>>>>>>>>> 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 at lst.de>
>>>>>>>>>>>     Reviewed-by: Jens Axboe
<axboe at kernel.dk>
>>>>>>>>>>>     Cc: Keith Busch <keith.busch
at intel.com>
>>>>>>>>>>>     Cc: linux-block at
vger.kernel.org
>>>>>>>>>>>     Cc: linux-nvme at
lists.infradead.org
>>>>>>>>>>>     Link:
http://lkml.kernel.org/r/20170626102058.10200-3-hch at lst.de
>>>>>>>>>>>     Signed-off-by: Thomas Gleixner
<tglx at linutronix.de>
>>>>>>>>>>>     Cc: Oleksandr Natalenko
<oleksandr at natalenko.name>
>>>>>>>>>>>     Cc: Mike Galbraith <efault
at gmx.de>
>>>>>>>>>>>     Signed-off-by: Greg
Kroah-Hartman <gregkh at linuxfoundation.org>
>>>>>>>>>>
>>>>>>>>>> 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 at de.ibm.com>
>>
>> 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

On 11/21/2017 09:21 PM, Jens Axboe wrote:
> 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 at lst.de>
>>>>>>>>>>>> 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 at lst.de>
>>>>>>>>>>>>     Reviewed-by: Jens Axboe
<axboe at kernel.dk>
>>>>>>>>>>>>     Cc: Keith Busch
<keith.busch at intel.com>
>>>>>>>>>>>>     Cc: linux-block at
vger.kernel.org
>>>>>>>>>>>>     Cc: linux-nvme at
lists.infradead.org
>>>>>>>>>>>>     Link:
http://lkml.kernel.org/r/20170626102058.10200-3-hch at lst.de
>>>>>>>>>>>>     Signed-off-by: Thomas
Gleixner <tglx at linutronix.de>
>>>>>>>>>>>>     Cc: Oleksandr Natalenko
<oleksandr at natalenko.name>
>>>>>>>>>>>>     Cc: Mike Galbraith
<efault at gmx.de>
>>>>>>>>>>>>     Signed-off-by: Greg
Kroah-Hartman <gregkh at linuxfoundation.org>
>>>>>>>>>>>
>>>>>>>>>>> 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 at
de.ibm.com>
>>>
>>> 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.
> 
I think we should tag it with:

Fixes: 4b855ad37194 ("blk-mq: Create hctx for each present CPU")

which should bring it into 4.13 stable and 4.14 stable. 4.12 stable seems EOL
anyway.