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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, Gui-Dong Han Subject: [PATCH] net: atheros: atl1e: use atomic functions with memory barriers for next_to_clean Date: Wed, 22 Apr 2026 17:37:17 +0800 Message-ID: <20260422093717.893646-1-hanguidong02@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" next_to_clean synchronizes Tx ring cleanup in atl1e_clean_tx_irq() with slot reuse in atl1e_tpd_avail(). atomic_set() and atomic_read() do not provide ordering. Without memory barriers, out-of-order execution can lead to concurrency bugs on weak memory architectures like ARM. For example, this can let the transmit path reuse a slot before tx_buffer->skb =3D NULL is visible and trigger the BUG_ON() in atl1e_tx_map(). This is a constructed scenario, and there might be other undiscovered, potentially more harmful bugs caused by this lack of ordering. Use atomic_set_release() and atomic_read_acquire() for next_to_clean. Fixes: a6a5325239c2 ("atl1e: Atheros L1E Gigabit Ethernet driver") Signed-off-by: Gui-Dong Han --- Found by auditing atomic operations used for synchronization. A similar fix can be found in 6df8e84aa6b5. Do not change atl1e_init_ring_ptrs(). Its atomic_set() runs during bring-up before NAPI and interrupts are enabled, so it is not a runtime publication point between Tx cleanup and Tx submission. In my opinion, implementing ad-hoc lockless algorithms directly within individual drivers is highly error-prone. To avoid these subtle memory ordering and barrier bugs, drivers should rely on established, well-tested kernel libraries like kfifo to handle this type of concurrency. --- drivers/net/ethernet/atheros/atl1e/atl1e_main.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/atheros/atl1e/atl1e_main.c b/drivers/net/= ethernet/atheros/atl1e/atl1e_main.c index 40290028580b..4ac8d4786820 100644 --- a/drivers/net/ethernet/atheros/atl1e/atl1e_main.c +++ b/drivers/net/ethernet/atheros/atl1e/atl1e_main.c @@ -1232,7 +1232,7 @@ static bool atl1e_clean_tx_irq(struct atl1e_adapter *= adapter) struct atl1e_tx_ring *tx_ring =3D &adapter->tx_ring; struct atl1e_tx_buffer *tx_buffer =3D NULL; u16 hw_next_to_clean =3D AT_READ_REGW(&adapter->hw, REG_TPD_CONS_IDX); - u16 next_to_clean =3D atomic_read(&tx_ring->next_to_clean); + u16 next_to_clean =3D atomic_read_acquire(&tx_ring->next_to_clean); =20 while (next_to_clean !=3D hw_next_to_clean) { tx_buffer =3D &tx_ring->tx_buffer[next_to_clean]; @@ -1259,7 +1259,7 @@ static bool atl1e_clean_tx_irq(struct atl1e_adapter *= adapter) next_to_clean =3D 0; } =20 - atomic_set(&tx_ring->next_to_clean, next_to_clean); + atomic_set_release(&tx_ring->next_to_clean, next_to_clean); =20 if (netif_queue_stopped(adapter->netdev) && netif_carrier_ok(adapter->netdev)) { @@ -1562,7 +1562,7 @@ static inline u16 atl1e_tpd_avail(struct atl1e_adapte= r *adapter) u16 next_to_use =3D 0; u16 next_to_clean =3D 0; =20 - next_to_clean =3D atomic_read(&tx_ring->next_to_clean); + next_to_clean =3D atomic_read_acquire(&tx_ring->next_to_clean); next_to_use =3D tx_ring->next_to_use; =20 return (u16)(next_to_clean > next_to_use) ? --=20 2.43.0