netdev - [PATCH V5 net] net: mana: Fix MANA VF unload when hardware is unresponsive

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Date: Wed,  5 Jul 2023 01:16:13 -0700
From: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
To: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	davem@...emloft.net,
	edumazet@...gle.com,
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	cai.huoqing@...ux.dev,
	ssengar@...ux.microsoft.com,
	vkuznets@...hat.com,
	tglx@...utronix.de,
	linux-hyperv@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
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Cc: stable@...r.kernel.org,
	schakrabarti@...rosoft.com,
	Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
Subject: [PATCH V5 net] net: mana: Fix MANA VF unload when hardware is unresponsive

When unloading the MANA driver, mana_dealloc_queues() waits for the MANA
hardware to complete any inflight packets and set the pending send count
to zero. But if the hardware has failed, mana_dealloc_queues()
could wait forever.

Fix this by adding a timeout to the wait. Set the timeout to 120 seconds,
which is a somewhat arbitrary value that is more than long enough for
functional hardware to complete any sends.

Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
---
V4 -> V5:
* Added fixes tag
* Changed the usleep_range from static to incremental value.
* Initialized timeout in the begining.
---
Signed-off-by: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 30 ++++++++++++++++---
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index a499e460594b..56b7074db1a2 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -2345,9 +2345,13 @@ int mana_attach(struct net_device *ndev)
 static int mana_dealloc_queues(struct net_device *ndev)
 {
 	struct mana_port_context *apc = netdev_priv(ndev);
+	unsigned long timeout = jiffies + 120 * HZ;
 	struct gdma_dev *gd = apc->ac->gdma_dev;
 	struct mana_txq *txq;
+	struct sk_buff *skb;
+	struct mana_cq *cq;
 	int i, err;
+	u32 tsleep;
 
 	if (apc->port_is_up)
 		return -EINVAL;
@@ -2363,15 +2367,33 @@ static int mana_dealloc_queues(struct net_device *ndev)
 	 * to false, but it doesn't matter since mana_start_xmit() drops any
 	 * new packets due to apc->port_is_up being false.
 	 *
-	 * Drain all the in-flight TX packets
+	 * Drain all the in-flight TX packets.
+	 * A timeout of 120 seconds for all the queues is used.
+	 * This will break the while loop when h/w is not responding.
+	 * This value of 120 has been decided here considering max
+	 * number of queues.
 	 */
+
 	for (i = 0; i < apc->num_queues; i++) {
 		txq = &apc->tx_qp[i].txq;
-
-		while (atomic_read(&txq->pending_sends) > 0)
-			usleep_range(1000, 2000);
+		tsleep = 1000;
+		while (atomic_read(&txq->pending_sends) > 0 &&
+		       time_before(jiffies, timeout)) {
+			usleep_range(tsleep, tsleep << 1);
+			tsleep <<= 1;
+		}
 	}
 
+	for (i = 0; i < apc->num_queues; i++) {
+		txq = &apc->tx_qp[i].txq;
+		cq = &apc->tx_qp[i].tx_cq;
+		while (atomic_read(&txq->pending_sends)) {
+			skb = skb_dequeue(&txq->pending_skbs);
+			mana_unmap_skb(skb, apc);
+			dev_consume_skb_any(skb);
+			atomic_sub(1, &txq->pending_sends);
+		}
+	}
 	/* We're 100% sure the queues can no longer be woken up, because
 	 * we're sure now mana_poll_tx_cq() can't be running.
 	 */
-- 
2.34.1