netdev - [PATCH net] 8139too: revisit napi_complete

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Message-ID: <1505765023.29839.32.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 18 Sep 2017 13:03:43 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: [PATCH net] 8139too: revisit napi_complete_done() usage

From: Eric Dumazet <edumazet@...gle.com>

It seems we have to be more careful in napi_complete_done()
use. This patch is not a revert, as it seems we can
avoid bug that Ville reported by moving the napi_complete_done()
test in the spinlock section.

Many thanks to Ville for detective work and all tests.

Fixes: 617f01211baf ("8139too: use napi_complete_done()")
Reported-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
---
 drivers/net/ethernet/realtek/8139too.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/realtek/8139too.c b/drivers/net/ethernet/realtek/8139too.c
index 89631753e79962d91456d93b71929af768917da1..cd2dbec331dd796f5296cd378561b3443f231673 100644
--- a/drivers/net/ethernet/realtek/8139too.c
+++ b/drivers/net/ethernet/realtek/8139too.c
@@ -2135,11 +2135,12 @@ static int rtl8139_poll(struct napi_struct *napi, int budget)
 	if (likely(RTL_R16(IntrStatus) & RxAckBits))
 		work_done += rtl8139_rx(dev, tp, budget);
 
-	if (work_done < budget && napi_complete_done(napi, work_done)) {
+	if (work_done < budget) {
 		unsigned long flags;
 
 		spin_lock_irqsave(&tp->lock, flags);
-		RTL_W16_F(IntrMask, rtl8139_intr_mask);
+		if (napi_complete_done(napi, work_done))
+			RTL_W16_F(IntrMask, rtl8139_intr_mask);
 		spin_unlock_irqrestore(&tp->lock, flags);
 	}
 	spin_unlock(&tp->rx_lock);