Re: [syzbot] [kvm?] [net?] [virt?] INFO: task hung in __vhost_worker_flush

[Stefano Garzarella]

On Mon, Aug 19, 2024 at 10:19:44AM -0500, Mike Christie wrote:
> On 8/16/24 1:17 PM, Michael S. Tsirkin wrote:
> > On Fri, Aug 16, 2024 at 11:10:32AM -0700, Sean Christopherson wrote:
> > > On Fri, Aug 16, 2024, syzbot wrote:
> > > > > On Wed, May 29, 2024, syzbot wrote:
> > > > > > Hello,
> > > > > >
> > > > > > syzbot found the following issue on:
> > > > > >
> > > > > > HEAD commit:    9b62e02e6336 Merge tag 'mm-hotfixes-stable-2024-05-25-09-1..
> > > > > > git tree:       upstream
> > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=16cb0eec980000
> > > > > > kernel config:  https://syzkaller.appspot.com/x/.config?x=3e73beba72b96506
> > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=7f3bbe59e8dd2328a990
> > > > > > compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > > > > >
> > > > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > > > >
> > > > > > Downloadable assets:
> > > > > > disk image: https://storage.googleapis.com/syzbot-assets/61b507f6e56c/disk-9b62e02e.raw.xz
> > > > > > vmlinux: https://storage.googleapis.com/syzbot-assets/6991f1313243/vmlinux-9b62e02e.xz
> > > > > > kernel image: https://storage.googleapis.com/syzbot-assets/65f88b96d046/bzImage-9b62e02e.xz
> > > > > >
> > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > > Reported-by: syzbot+7f3bbe59e8dd2328a990@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > > >
> > > > > #syz unset kvm
> > > >
> > > > The following labels did not exist: kvm
> > >
> > > Hrm, looks like there's no unset for a single subsytem, so:
> > >
> > > #syz set subsystems: net,virt
> >
> > Must be this patchset:
> >
> > https://lore.kernel.org/all/20240316004707.45557-1-michael.christie@xxxxxxxxxx/
> >
> > but I don't see anything obvious there to trigger it, and it's not
> > reproducible yet...
>
> Sorry, I missed the original post from May.
>
> I'm trying to replicate it now, but am not seeing it.
>
> The only time I've seen something similar is when the flush is actually waiting
> for a work item to complete, but I don't think the sysbot tests that for vsock.
> So, I think I'm hitting a race that I'm just not seeing yet. I'm just getting
> back from vacation, and will do some more testing/review this week.

Hi Mike,
looking at the syzbot virt monthly report I saw this issuse still open 
and with crashes:

  https://syzkaller.appspot.com/bug?extid=7f3bbe59e8dd2328a990

Have you had a chance to take a look?

Thanks,
Stefano