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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Stefan Chulski <stefanc@marvell.com>,
        Antoine Tenart <antoine.tenart@bootlin.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.14 014/109] net: mvpp2: fix a txq_done race condition
Date:   Tue, 16 Oct 2018 19:04:42 +0200
Message-Id: <20181016170525.748533128@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Antoine Tenart <antoine.tenart@bootlin.com>

[ Upstream commit 774268f3e51b53ed432a1ec516574fd5ba469398 ]

When no Tx IRQ is available, the txq_done() routine (called from
tx_done()) shouldn't be called from the polling function, as in such
case it is already called in the Tx path thanks to an hrtimer. This
mostly occurred when using PPv2.1, as the engine then do not have Tx
IRQs.

Fixes: edc660fa09e2 ("net: mvpp2: replace TX coalescing interrupts with hrtimer")
Reported-by: Stefan Chulski <stefanc@marvell.com>
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/marvell/mvpp2.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/marvell/mvpp2.c
+++ b/drivers/net/ethernet/marvell/mvpp2.c
@@ -6534,10 +6534,12 @@ static int mvpp2_poll(struct napi_struct
 				   cause_rx_tx & ~MVPP2_CAUSE_MISC_SUM_MASK);
 	}
 
-	cause_tx = cause_rx_tx & MVPP2_CAUSE_TXQ_OCCUP_DESC_ALL_MASK;
-	if (cause_tx) {
-		cause_tx >>= MVPP2_CAUSE_TXQ_OCCUP_DESC_ALL_OFFSET;
-		mvpp2_tx_done(port, cause_tx, qv->sw_thread_id);
+	if (port->has_tx_irqs) {
+		cause_tx = cause_rx_tx & MVPP2_CAUSE_TXQ_OCCUP_DESC_ALL_MASK;
+		if (cause_tx) {
+			cause_tx >>= MVPP2_CAUSE_TXQ_OCCUP_DESC_ALL_OFFSET;
+			mvpp2_tx_done(port, cause_tx, qv->sw_thread_id);
+		}
 	}
 
 	/* Process RX packets */