linux-kernel - Re: [PATCH rdma-next 4/5] RDMA/hns: Add reset process for RoCE in hip08

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Date:   Tue, 22 May 2018 14:26:12 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
Cc:     dledford@...hat.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, xavier.huwei@....com,
        lijun_nudt@....com
Subject: Re: [PATCH rdma-next 4/5] RDMA/hns: Add reset process for RoCE in
 hip08

On Fri, May 18, 2018 at 03:23:00PM +0800, Wei Hu (Xavier) wrote:
> 
> 
> On 2018/5/18 12:15, Jason Gunthorpe wrote:
> > On Fri, May 18, 2018 at 11:28:11AM +0800, Wei Hu (Xavier) wrote:
> >>
> >> On 2018/5/17 23:14, Jason Gunthorpe wrote:
> >>> On Thu, May 17, 2018 at 04:02:52PM +0800, Wei Hu (Xavier) wrote:
> >>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
> >>>> index 86ef15f..e1c44a6 100644
> >>>> +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
> >>>> @@ -774,6 +774,9 @@ static int hns_roce_cmq_send(struct hns_roce_dev *hr_dev,
> >>>>  	int ret = 0;
> >>>>  	int ntc;
> >>>>  
> >>>> +	if (hr_dev->is_reset)
> >>>> +		return 0;
> >>>> +
> >>>>  	spin_lock_bh(&csq->lock);
> >>>>  
> >>>>  	if (num > hns_roce_cmq_space(csq)) {
> >>>> @@ -4790,6 +4793,7 @@ static int hns_roce_hw_v2_init_instance(struct hnae3_handle *handle)
> >>>>  	return 0;
> >>>>  
> >>>>  error_failed_get_cfg:
> >>>> +	handle->priv = NULL;
> >>>>  	kfree(hr_dev->priv);
> >>>>  
> >>>>  error_failed_kzalloc:
> >>>> @@ -4803,14 +4807,70 @@ static void hns_roce_hw_v2_uninit_instance(struct hnae3_handle *handle,
> >>>>  {
> >>>>  	struct hns_roce_dev *hr_dev = (struct hns_roce_dev *)handle->priv;
> >>>>  
> >>>> +	if (!hr_dev)
> >>>> +		return;
> >>>> +
> >>>>  	hns_roce_exit(hr_dev);
> >>>> +	handle->priv = NULL;
> >>>>  	kfree(hr_dev->priv);
> >>>>  	ib_dealloc_device(&hr_dev->ib_dev);
> >>>>  }
> >>> Why are these hunks here? If init fails then uninit should not be
> >>> called, so why meddle with priv?
> >> In hns_roce_hw_v2_init_instance function, we evaluate handle->priv with 
> >> hr_dev,
> >> We want clear the value in hns_roce_hw_v2_uninit_instance function.
> >> So we can ensure no problem in RoCE driver.
> > What problem could happen?
> >
> > I keep removing unnecessary sets to null and checks of null, so please
> > don't add them if they cannot happen.
> >
> > Eg uninit should never be called with a null priv, that is a serious
> > logic mis-design someplace if it happens.
> >
> > Jason
> NIC driver call the registered reset_notify() function to finish the
> part of RoCE reset process.
> In RoCE driver,  when hnae3_reset_notify_type is HNAE3_UNINIT_CLIENT,
> we call hns_roce_hw_v2_uninit_instance(handle, false) to release the
> resources.
> when hnae3_reset_notify_type is HNAE3_INIT_CLIENT, we call
> hns_roce_hw_v2_init_instance.
> if hns_roce_hw_v2_init_instance failed, we should ensure no problem in
> the other callback
> function registered by RoCE driver.

Don't design things like this.

init/uninit are paired - do not call something uninit if it can be
called after init fails, or better, arrange to prevent that so things
are sane.

Jason