On Tue, Mar 26, 2019 at 11:17 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
>
> On 2019/3/25 下午10:02, Michael S. Tsirkin wrote:
> > Looks like more iotlb locking mess?
>
>
> Looking at the calltrace:
>
> [ 221.743675] =============================================
> [ 221.744297] [ INFO: possible recursive locking detected ]
> [ 221.744944] 4.7.0+ #1 Not tainted
> [ 221.745326] ---------------------------------------------
> [ 221.746128] syz-executor1/6823 is trying to acquire lock:
> [ 221.746737] (&vq->mutex){+.+...}, at: [<ffffffff84484b70>] vhost_process_iotlb_msg+0xe0/0x9e0
> [ 221.747789]
> [ 221.747789] but task is already holding lock:
> [ 221.748470] (&vq->mutex){+.+...}, at: [<ffffffff84484b70>] vhost_process_iotlb_msg+0xe0/0x9e0
> [ 221.749535]
> [ 221.749535] other info that might help us debug this:
> [ 221.750280] Possible unsafe locking scenario:
> [ 221.750280]
> [ 221.750946] CPU0
> [ 221.751232] ----
> [ 221.751523] lock(&vq->mutex);
> [ 221.751922] lock(&vq->mutex);
> [ 221.752339]
> [ 221.752339] *** DEADLOCK ***
> [ 221.752339]
>
> I could not think of a path that can hit this. And I could not reproduce with the reproducer in the link in net-next.
Looking at the bisection log, syzbot is able to reproduce this
super-reliably on multiple kernel revisions. Are you sure you are
using the right config/revision? What else can be in play? syzbot uses
VMs. The image is available.
> Thanks
>
>
> >
> > On Tue, Mar 19, 2019 at 10:21:00PM -0700, syzbot wrote:
> >> syzbot has bisected this bug to:
> >>
> >> commit 6b1e6cc7855b09a0a9bfa1d9f30172ba366f161c
> >> Author: Jason Wang <jasowang@xxxxxxxxxx>
> >> Date: Thu Jun 23 06:04:32 2016 +0000
> >>
> >> vhost: new device IOTLB API
> >>
> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1486ad27200000
> >> start commit: 6b1e6cc7 vhost: new device IOTLB API
> >> git tree: upstream
> >> final crash: https://syzkaller.appspot.com/x/report.txt?x=1686ad27200000
> >> console output: https://syzkaller.appspot.com/x/log.txt?x=1286ad27200000
> >> kernel config: https://syzkaller.appspot.com/x/.config?x=c94f9f0c0363db4b
> >> dashboard link: https://syzkaller.appspot.com/bug?extid=d21e6e297322a900c128
> >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=141db34d400000
> >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=108ef293400000
> >>
> >> Reported-by: syzbot+d21e6e297322a900c128@xxxxxxxxxxxxxxxxxxxxxxxxx
> >> Fixes: 6b1e6cc7 ("vhost: new device IOTLB API")
>
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