Re: Shutting down a VM with Kernel 4.14 will sometime hang and a reboot is the only way to recover.

[David Hill <dhill@redhat.com>]

On 2017-12-04 02:51 PM, David Hill wrote:
>
> On 2017-12-03 11:08 PM, Jason Wang wrote:
>>
>>
>> On 2017年12月02日 00:38, David Hill wrote:
>>>>
>>>> Finally, I reverted 581fe0ea61584d88072527ae9fb9dcb9d1f2783e too 
>>>> ... compiling and I'll keep you posted.
>>>
>>> So I'm still able to reproduce this issue even with reverting these 
>>> 3 commits.  Would you have other suspect commits ? 
>>
>> Thanks for the testing. No, I don't have other suspect commits.
>>
>> Looks like somebody else it hitting your issue too (see 
>> https://www.spinics.net/lists/netdev/msg468319.html)
>>
>> But he claims the issue were fixed by using qemu 2.10.1.
>>
>> So you may:
>>
>> -try to see if qemu 2.10.1 solves your issue
> It didn't solve it for him... it's only harder to reproduce. [1]
>> -if not, try to see if commit 
>> 2ddf71e23cc246e95af72a6deed67b4a50a7b81c ("net: add notifier hooks 
>> for devmap bpf map") is the first bad commit
> I'll try to see what I can do here
I'm looking at that commit and it's been introduced before v4.13 if I'm 
not mistaken while this issue appeared between v4.13 and v4.14-rc1 .  
Between those two releases, there're  1352 commits.
Is there a way to quickly know which commits are touching vhost-net, 
zerocopy ?


[ 7496.553044]  __schedule+0x2dc/0xbb0
[ 7496.553055]  ? trace_hardirqs_on+0xd/0x10
[ 7496.553074]  schedule+0x3d/0x90
[ 7496.553087]  vhost_net_ubuf_put_and_wait+0x73/0xa0 [vhost_net]
[ 7496.553100]  ? finish_wait+0x90/0x90
[ 7496.553115]  vhost_net_ioctl+0x542/0x910 [vhost_net]
[ 7496.553144]  do_vfs_ioctl+0xa6/0x6c0
[ 7496.553166]  SyS_ioctl+0x79/0x90
[ 7496.553182]  entry_SYSCALL_64_fastpath+0x1f/0xbe

>> -if not, maybe you can continue your bisection through git bisect skip
>>
> Some commits are so broken that the system won't boot ...  What I fear 
> is that if I git bisect skip those commits, I'll also skip the commit 
> culprit of my original problem
>
> [1] https://www.spinics.net/lists/netdev/msg469887.html