linux-kernel - [PATCH net,v2] hv_netvsc: Fix napi reschedule while receive completion is busy

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Message-Id: <20180717171113.6390-1-haiyangz@linuxonhyperv.com>
Date:   Tue, 17 Jul 2018 17:11:13 +0000
From:   Haiyang Zhang <haiyangz@...uxonhyperv.com>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     haiyangz@...rosoft.com, kys@...rosoft.com, sthemmin@...rosoft.com,
        olaf@...fle.de, vkuznets@...hat.com, devel@...uxdriverproject.org,
        linux-kernel@...r.kernel.org,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: [PATCH net,v2] hv_netvsc: Fix napi reschedule while receive completion is busy

From: Haiyang Zhang <haiyangz@...rosoft.com>

If out ring is full temporarily and receive completion cannot go out,
we may still need to reschedule napi if certain conditions are met.
Otherwise the napi poll might be stopped forever, and cause network
disconnect.

Fixes: 7426b1a51803 ("netvsc: optimize receive completions")
Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
---
 drivers/net/hyperv/netvsc.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 8e9d0ee1572b..31c3d77b4733 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1274,6 +1274,7 @@ int netvsc_poll(struct napi_struct *napi, int budget)
 	struct hv_device *device = netvsc_channel_to_device(channel);
 	struct net_device *ndev = hv_get_drvdata(device);
 	int work_done = 0;
+	int ret;
 
 	/* If starting a new interval */
 	if (!nvchan->desc)
@@ -1285,16 +1286,18 @@ int netvsc_poll(struct napi_struct *napi, int budget)
 		nvchan->desc = hv_pkt_iter_next(channel, nvchan->desc);
 	}
 
-	/* If send of pending receive completions suceeded
-	 *   and did not exhaust NAPI budget this time
-	 *   and not doing busy poll
+	/* Send any pending receive completions */
+	ret = send_recv_completions(ndev, net_device, nvchan);
+
+	/* If it did not exhaust NAPI budget this time
+	 *  and not doing busy poll
 	 * then re-enable host interrupts
-	 *     and reschedule if ring is not empty.
+	 *  and reschedule if ring is not empty
+	 *   or sending receive completion failed.
 	 */
-	if (send_recv_completions(ndev, net_device, nvchan) == 0 &&
-	    work_done < budget &&
+	if (work_done < budget &&
 	    napi_complete_done(napi, work_done) &&
-	    hv_end_read(&channel->inbound) &&
+	    (ret || hv_end_read(&channel->inbound)) &&
 	    napi_schedule_prep(napi)) {
 		hv_begin_read(&channel->inbound);
 		__napi_schedule(napi);
-- 
2.17.1