On Sat, Jan 26, 2019 at 09:47:42AM +0800, Wei Hu (Xavier) wrote:
>
>
> On 2019/1/26 5:50, Jason Gunthorpe wrote:
> > On Fri, Jan 25, 2019 at 10:15:40AM +0800, Wei Hu (Xavier) wrote:
> >>
> >> On 2019/1/25 2:31, Jason Gunthorpe wrote:
> >>> On Thu, Jan 24, 2019 at 11:13:29AM +0800, Wei Hu (Xavier) wrote:
> >>>> On 2019/1/24 6:40, Jason Gunthorpe wrote:
> >>>>> On Sat, Jan 19, 2019 at 11:36:06AM +0800, Wei Hu (Xavier) wrote:
> >>>>>
> >>>>>> +static int hns_roce_v2_cmd_hw_resetting(struct hns_roce_dev *hr_dev,
> >>>>>> + unsigned long instance_stage,
> >>>>>> + unsigned long reset_stage)
> >>>>>> +{
> >>>>>> + struct hns_roce_v2_priv *priv = (struct hns_roce_v2_priv *)hr_dev->priv;
> >>>>>> + struct hnae3_handle *handle = priv->handle;
> >>>>>> + const struct hnae3_ae_ops *ops = handle->ae_algo->ops;
> >>>>>> + unsigned long end;
> >>>>>> +
> >>>>>> + /* When hardware reset is detected, we should stop sending mailbox&cmq
> >>>>>> + * to hardware, and wait until hardware reset finished. If now
> >>>>>> + * in .init_instance() function, we should exit with error. If now at
> >>>>>> + * HNAE3_INIT_CLIENT stage of soft reset process, we should exit with
> >>>>>> + * error, and then HNAE3_INIT_CLIENT related process can rollback the
> >>>>>> + * operation like notifing hardware to free resources, HNAE3_INIT_CLIENT
> >>>>>> + * related process will exit with error to notify NIC driver to
> >>>>>> + * reschedule soft reset process once again.
> >>>>>> + */
> >>>>>> + end = msecs_to_jiffies(HNS_ROCE_V2_HW_RST_TIMEOUT) + jiffies;
> >>>>>> + while (ops->get_hw_reset_stat(handle) && time_before(jiffies, end))
> >>>>>> + udelay(1);
> >>>>> I thought you were getting rid of these loops?
> >>>> Hi, Jason
> >>>>
> >>>> Upper applications maybe notify driver to issue mailbox or CMD
> >>>> commands to hardware, some commands used to cancel resources,
> >>>> destory bt/destory cq/unreg mr/destory qp etc. when such
> >>>> commands are executed successfully, the hardware engine will
> >>>> no longer access some memory registered by the driver.
> >>>>
> >>>> When reset occurs, it is possible for upper applications notify driver
> >>>> to issue mailbox or CMD commands, we need to wait until hardware
> >>>> reset finished to ensure that hardware no longer accesses related
> >>>> memory.
> >>> You should not wait for things using loops like the above.
> >> Hi, Jason
> >>
> >> Are your comments foucsing on udelay? If not, thanks for your detail
> >> information.
> >> In hns3 RoCE driver, some CMQ/mailbox operation are called inside
> >> the lock,
> >> we can't use msleep in the lock, otherwise it will cause deadlock.
> >> When reset occurs, RDMA service cannot be provided normally, I think
> >> in this
> >> case using udelay will not have a great impact.
> > You should not use any kind of sleep call in a loop like this.
> Hi, Jason
>
> OK, I got your opinion and will modify it in v3 patch as below:
>
> end = msecs_to_jiffies(HNS_ROCE_V2_HW_RST_TIMEOUT) + jiffies;
> while (time_before(jiffies, end))
> if (!ops->get_hw_reset_stat(handle))
> break;
You shouldn't be looping like this at all, a busy loop is worse, don't
try and open code spinlocks.
Jason
