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    Subject[ 69/82] r8169: fix early queue wake-up.
    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 <eric.dumazet@gmail.com>
    Cc: Hayes Wang <hayeswang@realtek.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    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)) {



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