[PATCH AUTOSEL 5.4 036/130] r8169: use READ_ONCE in rtl_tx_slots_avail

Sasha Levin
2020-12-23T02:19:59Z

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 fd5adb0c54d29..fca8252b4f21d 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5856,7 +5856,8 @@ 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