netdev - [RFC PATCH net] ibmvnic: complete dev->poll nicely during adapter reset

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Date:   Fri,  5 Mar 2021 01:44:56 -0600
From:   Lijun Pan <ljp@...ux.ibm.com>
To:     netdev@...r.kernel.org
Cc:     kuba@...nel.org, davem@...emloft.net, sukadev@...ux.ibm.com,
        drt@...ux.ibm.com, tlfalcon@...ux.ibm.com,
        Lijun Pan <ljp@...ux.ibm.com>
Subject: [RFC PATCH net] ibmvnic: complete dev->poll nicely during adapter reset

The reset path will call ibmvnic_cleanup->ibmvnic_napi_disable
->napi_disable(). This is supposed to stop the polling.
Commit 21ecba6c48f9 ("ibmvnic: Exit polling routine correctly
during adapter reset") reported that the during device reset,
polling routine never completed and napi_disable slept indefinitely.
In order to solve that problem, resetting bit was checked and
napi_complete_done was called before dev->poll::ibmvnic_poll exited.

Checking for resetting bit in dev->poll is racy because resetting
bit may be false while being checked, but turns true immediately
afterwards.

Hence we call napi_complete in ibmvnic_napi_disable, which avoids
the racing with resetting, and makes sure dev->poll and napi_disalbe
completes before reset routine actually releases resources.

Fixes: 21ecba6c48f9 ("ibmvnic: Exit polling routine correctly during adapter reset")
Signed-off-by: Lijun Pan <ljp@...ux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index b6102ccf9b90..338d3d071cec 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -785,6 +785,7 @@ static void ibmvnic_napi_disable(struct ibmvnic_adapter *adapter)
 
 	for (i = 0; i < adapter->req_rx_queues; i++) {
 		netdev_dbg(adapter->netdev, "Disabling napi[%d]\n", i);
+		napi_complete(&adapter->napi[i]);
 		napi_disable(&adapter->napi[i]);
 	}
 
@@ -2455,13 +2456,6 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 		u16 offset;
 		u8 flags = 0;
 
-		if (unlikely(test_bit(0, &adapter->resetting) &&
-			     adapter->reset_reason != VNIC_RESET_NON_FATAL)) {
-			enable_scrq_irq(adapter, rx_scrq);
-			napi_complete_done(napi, frames_processed);
-			return frames_processed;
-		}
-
 		if (!pending_scrq(adapter, rx_scrq))
 			break;
 		next = ibmvnic_next_scrq(adapter, rx_scrq);
-- 
2.23.0