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    Subject[PATCH AUTOSEL 5.10 077/217] r8169: use READ_ONCE in rtl_tx_slots_avail
    Date
    From: Heiner Kallweit <hkallweit1@gmail.com>

    [ Upstream commit 95f3c5458dfa5856bb110e31d156e00d894d0134 ]

    tp->dirty_tx and tp->cur_tx may be changed by a racing rtl_tx() or
    rtl8169_start_xmit(). Use READ_ONCE() to annotate the races and ensure
    that the compiler doesn't use cached values.

    Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
    Link: https://lore.kernel.org/r/5676fee3-f6b4-84f2-eba5-c64949a371ad@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/ethernet/realtek/r8169_main.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
    index 85d9c3e30c699..67918feed307e 100644
    --- a/drivers/net/ethernet/realtek/r8169_main.c
    +++ b/drivers/net/ethernet/realtek/r8169_main.c
    @@ -4173,7 +4173,8 @@ static bool rtl8169_tso_csum_v2(struct rtl8169_private *tp,
    static bool rtl_tx_slots_avail(struct rtl8169_private *tp,
    unsigned int nr_frags)
    {
    - unsigned int slots_avail = tp->dirty_tx + NUM_TX_DESC - tp->cur_tx;
    + unsigned int slots_avail = READ_ONCE(tp->dirty_tx) + NUM_TX_DESC
    + - READ_ONCE(tp->cur_tx);

    /* A skbuff with nr_frags needs nr_frags+1 entries in the tx queue */
    return slots_avail > nr_frags;
    --
    2.27.0
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