linux-kernel - [PATCH 3.16 318/328] r8169: fix NAPI handling under high load

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Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
        "Heiner Kallweit" <hkallweit1@...il.com>
Subject: [PATCH 3.16 318/328] r8169: fix NAPI handling under high load

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Heiner Kallweit <hkallweit1@...il.com>

commit 6b839b6cf9eada30b086effb51e5d6076bafc761 upstream.

rtl_rx() and rtl_tx() are called only if the respective bits are set
in the interrupt status register. Under high load NAPI may not be
able to process all data (work_done == budget) and it will schedule
subsequent calls to the poll callback.
rtl_ack_events() however resets the bits in the interrupt status
register, therefore subsequent calls to rtl8169_poll() won't call
rtl_rx() and rtl_tx() - chip interrupts are still disabled.

Fix this by calling rtl_rx() and rtl_tx() independent of the bits
set in the interrupt status register. Both functions will detect
if there's nothing to do for them.

Fixes: da78dbff2e05 ("r8169: remove work from irq handler.")
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/ethernet/realtek/r8169.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -6417,17 +6417,15 @@ static int rtl8169_poll(struct napi_stru
 	struct rtl8169_private *tp = container_of(napi, struct rtl8169_private, napi);
 	struct net_device *dev = tp->dev;
 	u16 enable_mask = RTL_EVENT_NAPI | tp->event_slow;
-	int work_done= 0;
+	int work_done;
 	u16 status;

 	status = rtl_get_events(tp);
 	rtl_ack_events(tp, status & ~tp->event_slow);

-	if (status & RTL_EVENT_NAPI_RX)
-		work_done = rtl_rx(dev, tp, (u32) budget);
+	work_done = rtl_rx(dev, tp, (u32) budget);

-	if (status & RTL_EVENT_NAPI_TX)
-		rtl_tx(dev, tp);
+	rtl_tx(dev, tp);

 	if (status & tp->event_slow) {
 		enable_mask &= ~tp->event_slow;