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SubjectRe: INFO: task hung in vhost_net_stop_vq
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On 2019/3/26 下午6:28, Dmitry Vyukov wrote:
> On Tue, Mar 26, 2019 at 11:17 AM Jason Wang<jasowang@redhat.com> 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.
>
>

Yes, looks like the reason is vhost accept zero size iova range which
lead a infinite loop when trying to translate iova. Will post a patch to
fix this.

Thanks

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