netdev - [PATCH net-next] net: ibm: replenish rx pool and poll less frequently

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Date:   Wed,  2 Jun 2021 12:01:56 -0500
From:   Lijun Pan <lijunp213@...il.com>
To:     netdev@...r.kernel.org
Cc:     Lijun Pan <lijunp213@...il.com>
Subject: [PATCH net-next] net: ibm: replenish rx pool and poll less frequently

The old mechanism replenishes rx pool even only one frames is processed in
the poll function, which causes lots of overheads. The old mechanism
restarts polling until processed frames reaches the budget, which can
cause the poll function to loop into restart_poll 63 times at most and to
call replenish_rx_poll 63 times at most. This will cause soft lockup very
easily. So, don't replenish too often, and don't goto restart_poll in each
poll function. If there are pending descriptors, fetch them in the next
poll instance.

Signed-off-by: Lijun Pan <lijunp213@...il.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index ffb2a91750c7..fae1eaa39dd0 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2435,7 +2435,6 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 	frames_processed = 0;
 	rx_scrq = adapter->rx_scrq[scrq_num];
 
-restart_poll:
 	while (frames_processed < budget) {
 		struct sk_buff *skb;
 		struct ibmvnic_rx_buff *rx_buff;
@@ -2512,20 +2511,12 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 	}
 
 	if (adapter->state != VNIC_CLOSING &&
-	    ((atomic_read(&adapter->rx_pool[scrq_num].available) <
-	      adapter->req_rx_add_entries_per_subcrq / 2) ||
-	      frames_processed < budget))
+	    (atomic_read(&adapter->rx_pool[scrq_num].available) <
+	      adapter->req_rx_add_entries_per_subcrq / 2))
 		replenish_rx_pool(adapter, &adapter->rx_pool[scrq_num]);
 	if (frames_processed < budget) {
-		if (napi_complete_done(napi, frames_processed)) {
+		if (napi_complete_done(napi, frames_processed))
 			enable_scrq_irq(adapter, rx_scrq);
-			if (pending_scrq(adapter, rx_scrq)) {
-				if (napi_reschedule(napi)) {
-					disable_scrq_irq(adapter, rx_scrq);
-					goto restart_poll;
-				}
-			}
-		}
 	}
 	return frames_processed;
 }
-- 
2.23.0