Commit 7b3d770c authored by Chuck Lever's avatar Chuck Lever Committed by Anna Schumaker
Browse files

xprtrdma: Re-arm after missed events 



ib_req_notify_cq(IB_CQ_REPORT_MISSED_EVENTS) returns a positive
value if WCs were added to a CQ after the last completion upcall
but before the CQ has been re-armed.

Commit 7f23f6f6 ("xprtrmda: Reduce lock contention in
completion handlers") assumed that when ib_req_notify_cq() returned
a positive RC, the CQ had also been successfully re-armed, making
it safe to return control to the provider without losing any
completion signals. That is an invalid assumption.

Change both completion handlers to continue polling while
ib_req_notify_cq() returns a positive value.

Fixes: 7f23f6f6 ("xprtrmda: Reduce lock contention in ...")
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Reviewed-by: default avatarSagi Grimberg <sagig@mellanox.com>
Reviewed-by: default avatarDevesh Sharma <devesh.sharma@avagotech.com>
Tested-By: default avatarDevesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent a0451788

net/sunrpc/xprtrdma/verbs.c

+10 −56
Original line number Diff line number Diff line
@@ -179,38 +179,17 @@ rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep) 
	return 0;

}



/*

 * Handle send, fast_reg_mr, and local_inv completions.

 *

 * Send events are typically suppressed and thus do not result

 * in an upcall. Occasionally one is signaled, however. This

 * prevents the provider's completion queue from wrapping and

 * losing a completion.

/* Handle provider send completion upcalls.

 */

static void

rpcrdma_sendcq_upcall(struct ib_cq *cq, void *cq_context)

{

	struct rpcrdma_ep *ep = (struct rpcrdma_ep *)cq_context;

	int rc;



	rc = rpcrdma_sendcq_poll(cq, ep);

	if (rc) {

		dprintk("RPC:       %s: ib_poll_cq failed: %i\n",

			__func__, rc);

		return;

	}



	rc = ib_req_notify_cq(cq,

			IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);

	if (rc == 0)

		return;

	if (rc < 0) {

		dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",

			__func__, rc);

		return;

	}



	do {

		rpcrdma_sendcq_poll(cq, ep);

	} while (ib_req_notify_cq(cq, IB_CQ_NEXT_COMP |

				  IB_CQ_REPORT_MISSED_EVENTS) > 0);

}



static void
@@ -274,42 +253,17 @@ out_schedule: 
	return rc;

}



/*

 * Handle receive completions.

 *

 * It is reentrant but processes single events in order to maintain

 * ordering of receives to keep server credits.

 *

 * It is the responsibility of the scheduled tasklet to return

 * recv buffers to the pool. NOTE: this affects synchronization of

 * connection shutdown. That is, the structures required for

 * the completion of the reply handler must remain intact until

 * all memory has been reclaimed.

/* Handle provider receive completion upcalls.

 */

static void

rpcrdma_recvcq_upcall(struct ib_cq *cq, void *cq_context)

{

	struct rpcrdma_ep *ep = (struct rpcrdma_ep *)cq_context;

	int rc;



	rc = rpcrdma_recvcq_poll(cq, ep);

	if (rc) {

		dprintk("RPC:       %s: ib_poll_cq failed: %i\n",

			__func__, rc);

		return;

	}



	rc = ib_req_notify_cq(cq,

			IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);

	if (rc == 0)

		return;

	if (rc < 0) {

		dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",

			__func__, rc);

		return;

	}



	do {

		rpcrdma_recvcq_poll(cq, ep);

	} while (ib_req_notify_cq(cq, IB_CQ_NEXT_COMP |

				  IB_CQ_REPORT_MISSED_EVENTS) > 0);

}



static void

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