[ 69/82] r8169: fix early queue wake-up.
From: Ben Hutchings <hidden>
Date: 2012-06-08 05:13:44
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8169 10/100/1000 gigabit ethernet driver, networking drivers, the rest · Maintainers:
Heiner Kallweit, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Francois Romieu <romieu@fr.zoreil.com> [ Upstream commit ae1f23fb433ac0aaff8aeaa5a7b14348e9aa8277 ] With infinite gratitude to Eric Dumazet for allowing me to identify the error. Signed-off-by: Francois Romieu <romieu@fr.zoreil.com> Acked-by: Eric Dumazet <redacted> Cc: Hayes Wang <redacted> Signed-off-by: Ben Hutchings <redacted> --- drivers/net/ethernet/realtek/r8169.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 5104d76..5f3fa32 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c@@ -5561,7 +5561,18 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb, RTL_W8(TxPoll, NPQ); if (TX_BUFFS_AVAIL(tp) < MAX_SKB_FRAGS) { + /* Avoid wrongly optimistic queue wake-up: rtl_tx thread must + * not miss a ring update when it notices a stopped queue. + */ + smp_wmb(); netif_stop_queue(dev); + /* Sync with rtl_tx: + * - publish queue status and cur_tx ring index (write barrier) + * - refresh dirty_tx ring index (read barrier). + * May the current thread have a pessimistic view of the ring + * status and forget to wake up queue, a racing rtl_tx thread + * can't. + */ smp_mb(); if (TX_BUFFS_AVAIL(tp) >= MAX_SKB_FRAGS) netif_wake_queue(dev);
@@ -5663,6 +5674,13 @@ static void rtl8169_tx_interrupt(struct net_device *dev, if (tp->dirty_tx != dirty_tx) { tp->dirty_tx = dirty_tx; + /* Sync with rtl8169_start_xmit: + * - publish dirty_tx ring index (write barrier) + * - refresh cur_tx ring index and queue status (read barrier) + * May the current thread miss the stopped queue condition, + * a racing xmit thread can only have a right view of the + * ring status. + */ smp_mb(); if (netif_queue_stopped(dev) && (TX_BUFFS_AVAIL(tp) >= MAX_SKB_FRAGS)) {