On 3/21/2018 3:02 PM, Jason Gunthorpe wrote:
> On Mon, Mar 19, 2018 at 10:47:45PM -0400, Sinan Kaya wrote:
>> diff --git a/drivers/infiniband/hw/i40iw/i40iw_uk.c b/drivers/infiniband/hw/i40iw/i40iw_uk.c
>> index 8afa5a6..7f0ebed 100644
>> +++ b/drivers/infiniband/hw/i40iw/i40iw_uk.c
>> @@ -723,7 +723,7 @@ static void i40iw_cq_request_notification(struct i40iw_cq_uk *cq,
>>
>> wmb(); /* make sure WQE is populated before valid bit is set */
>>
>> - writel(cq->cq_id, cq->cqe_alloc_reg);
>> + writel_relaxed(cq->cq_id, cq->cqe_alloc_reg);
>> }
>
> Ah, this one is probably not OK, i40iw_cq_request_notification is
> called here:
>
> spin_lock_irqsave(&iwcq->lock, flags);
> ukcq->ops.iw_cq_request_notification(ukcq, cq_notify);
> spin_unlock_irqrestore(&iwcq->lock, flags);
>
> So this needs to add mmmiomb(); to keep the same semantics.
>
> Generally I think you need to be very careful to ensure that any
> conversion to _relaxed isn't contained by a spinlock, or the mmiomb()
> is present.
>
> Maybe even do a first series with this obviously correct pattern:
>
> wmb();
> writel() -> writel_relaxed()
> writel() -> writel_relaxed()
> [..]
> mmiowmb();
Good catch. I changed it as follows:
+++ b/drivers/infiniband/hw/i40iw/i40iw_uk.c
@@ -723,7 +723,8 @@ static void i40iw_cq_request_notification(struct i40iw_cq_uk *cq,
wmb(); /* make sure WQE is populated before valid bit is set */
- writel(cq->cq_id, cq->cqe_alloc_reg);
+ writel_relaxed(cq->cq_id, cq->cqe_alloc_reg);
+ mmiowb();
}
>
> Jason
>
--
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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