Messages in this thread | | | Date | Wed, 21 Mar 2018 14:02:53 -0600 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v4 3/6] RDMA/i40iw: Eliminate duplicate barriers on weakly-ordered archs |
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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();
Jason
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