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Subject: Re: [PATCH v1 1/3] svcrdma: Fewer calls to wake_up() in Send
 completion handler
To:     Chuck Lever <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org,
        linux-rdma@vger.kernel.org
References: <162731055652.13580.8774661104190191089.stgit@klimt.1015granger.net>
 <162731081843.13580.15415936872318036839.stgit@klimt.1015granger.net>
From:   Tom Talpey <tom@talpey.com>
Message-ID: <e25bd7be-6bcc-cf7d-efcf-1ac39d411431@talpey.com>
Date:   Mon, 26 Jul 2021 12:50:02 -0400
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On 7/26/2021 10:46 AM, Chuck Lever wrote:
>   /**
>    * svc_rdma_wc_send - Invoked by RDMA provider for each polled Send WC
>    * @cq: Completion Queue context
> @@ -275,11 +289,9 @@ static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc)
>   
>   	trace_svcrdma_wc_send(wc, &ctxt->sc_cid);
>   
> +	svc_rdma_wake_send_waiters(rdma, 1);
>   	complete(&ctxt->sc_done);
>   
> -	atomic_inc(&rdma->sc_sq_avail);
> -	wake_up(&rdma->sc_send_wait);

This appears to change the order of wake_up() vs complete().
Is that intentional? Is there any possibility of a false
scheduler activation, later leading to a second wakeup or poll?

Tom.