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SubjectRe: [PATCH V2 rdma-next 2/3] RDMA/hns: Fix the chip hanging caused by sending mailbox&CMQ during reset
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On 2019/1/29 11:45, Jason Gunthorpe wrote:
> On Tue, Jan 29, 2019 at 10:18:40AM +0800, Wei Hu (Xavier) wrote:
>>
>> On 2019/1/29 2:27, Jason Gunthorpe wrote:
>>> 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.
>> Hi, Jason
>>
>> OK, we will modify some places calling CMQ/mailbox operation,
>> replace spinlock with mutex, and add msleep here:
>>
>> end = msecs_to_jiffies(HNS_ROCE_V2_HW_RST_TIMEOUT) + jiffies;
>> while (time_before(jiffies, end)) {
>> if (!ops->get_hw_reset_stat(handle))
>> break;
>> msleep(20);
>> }
> How many more times do I have to say not to code spin loops like
> this???? Use proper locking!
Hi, Jason
Ok, Thanks for your comments.
And we removed the loop operation here and sent patch v4. Thanks

Regards
Xavier
> Jason
>
> .
>


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