Re: [PATCH v4 for-next 1/2] RDMA/hns: Add the workqueue framework for flush cqe handler

["Liuyixian (Eason)" <liuyixian@huawei.com>]

On 2019/12/26 16:19, Leon Romanovsky wrote:
> On Tue, Dec 24, 2019 at 09:10:13PM +0800, Yixian Liu wrote:
>> HiP08 RoCE hardware lacks ability(a known hardware problem) to flush
>> outstanding WQEs if QP state gets into errored mode for some reason.
>> To overcome this hardware problem and as a workaround, when QP is
>> detected to be in errored state during various legs like post send,
>> post receive etc [1], flush needs to be performed from the driver.
>>
>> The earlier patch[1] sent to solve the hardware limitation explained
>> in the cover-letter had a bug in the software flushing leg. It
>> acquired mutex while modifying QP state to errored state and while
>> conveying it to the hardware using the mailbox. This caused leg to
>> sleep while holding spin-lock and caused crash.
>>
>> Suggested Solution:
>> we have proposed to defer the flushing of the QP in the Errored state
>> using the workqueue to get around with the limitation of our hardware.
>>
>> This patch adds the framework of the workqueue and the flush handler
>> function.
>>
>> [1] https://patchwork.kernel.org/patch/10534271/
>>
>> Signed-off-by: Yixian Liu <liuyixian@huawei.com>
>> Reviewed-by: Salil Mehta <salil.mehta@huawei.com>
>> ---
>>  drivers/infiniband/hw/hns/hns_roce_device.h |  2 ++
>>  drivers/infiniband/hw/hns/hns_roce_hw_v2.c  |  4 +--
>>  drivers/infiniband/hw/hns/hns_roce_qp.c     | 43 +++++++++++++++++++++++++++++
>>  3 files changed, 47 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/infiniband/hw/hns/hns_roce_device.h b/drivers/infiniband/hw/hns/hns_roce_device.h
>> index a1b712e..292b712 100644
>> --- a/drivers/infiniband/hw/hns/hns_roce_device.h
>> +++ b/drivers/infiniband/hw/hns/hns_roce_device.h
>> @@ -906,6 +906,7 @@ struct hns_roce_caps {
>>  struct hns_roce_work {
>>  	struct hns_roce_dev *hr_dev;
>>  	struct work_struct work;
>> +	struct hns_roce_qp *hr_qp;
>>  	u32 qpn;
>>  	u32 cqn;
>>  	int event_type;
>> @@ -1226,6 +1227,7 @@ struct ib_qp *hns_roce_create_qp(struct ib_pd *ib_pd,
>>  				 struct ib_udata *udata);
>>  int hns_roce_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr,
>>  		       int attr_mask, struct ib_udata *udata);
>> +void init_flush_work(struct hns_roce_dev *hr_dev, struct hns_roce_qp *hr_qp);
>>  void *get_recv_wqe(struct hns_roce_qp *hr_qp, int n);
>>  void *get_send_wqe(struct hns_roce_qp *hr_qp, int n);
>>  void *get_send_extend_sge(struct hns_roce_qp *hr_qp, int n);
>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>> index 907c951..ec48e7e 100644
>> --- a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>> +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>> @@ -5967,8 +5967,8 @@ static int hns_roce_v2_init_eq_table(struct hns_roce_dev *hr_dev)
>>  		goto err_request_irq_fail;
>>  	}
>>
>> -	hr_dev->irq_workq =
>> -		create_singlethread_workqueue("hns_roce_irq_workqueue");
>> +	hr_dev->irq_workq = alloc_workqueue("hns_roce_irq_workqueue",
>> +					    WQ_MEM_RECLAIM, 0);
> 
> Combination of WQ_MEM_RECLAIM flag with kzalloc inside init_flush_work()
> can't be correct at the same time.
> 
Thanks a lot for reminder!
I will check with previous discussion on the flag WQ_MEM_RECLAIM and fix it next version.