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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Subject: [PATCH net-next v3 2/2] net: dsa: yt921x: Protect MIB stats with a lock Date: Mon, 5 Jan 2026 10:09:01 +0800 Message-ID: <20260105020905.3522484-3-mmyangfl@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260105020905.3522484-1-mmyangfl@gmail.com> References: <20260105020905.3522484-1-mmyangfl@gmail.com> 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" 64bit variables might not be atomic on 32bit architectures, thus cannot be made lock-free. Protect them with a spin lock since get_stats64() cannot sleep. Signed-off-by: David Yang --- drivers/net/dsa/yt921x.c | 63 ++++++++++++++++++++++++++-------------- drivers/net/dsa/yt921x.h | 5 ++++ 2 files changed, 46 insertions(+), 22 deletions(-) diff --git a/drivers/net/dsa/yt921x.c b/drivers/net/dsa/yt921x.c index 5e4e8093ba16..98ee517e0675 100644 --- a/drivers/net/dsa/yt921x.c +++ b/drivers/net/dsa/yt921x.c @@ -666,22 +666,16 @@ yt921x_mbus_ext_init(struct yt921x_priv *priv, struct= device_node *mnp) static int yt921x_read_mib(struct yt921x_priv *priv, int port) { struct yt921x_port *pp =3D &priv->ports[port]; + struct yt921x_mib *mib_new =3D &pp->mib_new; struct device *dev =3D to_device(priv); struct yt921x_mib *mib =3D &pp->mib; + u64 rx_frames; + u64 tx_frames; int res =3D 0; =20 - /* Reading of yt921x_port::mib is not protected by a lock and it's vain - * to keep its consistency, since we have to read registers one by one - * and there is no way to make a snapshot of MIB stats. - * - * Writing (by this function only) is and should be protected by - * reg_lock. - */ - for (size_t i =3D 0; i < ARRAY_SIZE(yt921x_mib_descs); i++) { const struct yt921x_mib_desc *desc =3D &yt921x_mib_descs[i]; u32 reg =3D YT921X_MIBn_DATA0(port) + desc->offset; - u64 *valp =3D &((u64 *)mib)[i]; u32 val0; u64 val; =20 @@ -690,7 +684,7 @@ static int yt921x_read_mib(struct yt921x_priv *priv, in= t port) break; =20 if (desc->size <=3D 1) { - u64 old_val =3D *valp; + u64 old_val =3D ((u64 *)mib)[i]; =20 val =3D (old_val & ~(u64)U32_MAX) | val0; if (val < old_val) @@ -704,22 +698,31 @@ static int yt921x_read_mib(struct yt921x_priv *priv, = int port) val =3D ((u64)val1 << 32) | val0; } =20 - WRITE_ONCE(*valp, val); + ((u64 *)mib_new)[i] =3D val; } =20 - pp->rx_frames =3D mib->rx_64byte + mib->rx_65_127byte + - mib->rx_128_255byte + mib->rx_256_511byte + - mib->rx_512_1023byte + mib->rx_1024_1518byte + - mib->rx_jumbo; - pp->tx_frames =3D mib->tx_64byte + mib->tx_65_127byte + - mib->tx_128_255byte + mib->tx_256_511byte + - mib->tx_512_1023byte + mib->tx_1024_1518byte + - mib->tx_jumbo; - - if (res) + if (res) { dev_err(dev, "Failed to %s port %d: %i\n", "read stats for", port, res); - return res; + return res; + } + + rx_frames =3D mib->rx_64byte + mib->rx_65_127byte + + mib->rx_128_255byte + mib->rx_256_511byte + + mib->rx_512_1023byte + mib->rx_1024_1518byte + + mib->rx_jumbo; + tx_frames =3D mib->tx_64byte + mib->tx_65_127byte + + mib->tx_128_255byte + mib->tx_256_511byte + + mib->tx_512_1023byte + mib->tx_1024_1518byte + + mib->tx_jumbo; + + spin_lock(&pp->stats_lock); + *mib =3D *mib_new; + pp->rx_frames =3D rx_frames; + pp->tx_frames =3D tx_frames; + spin_unlock(&pp->stats_lock); + + return 0; } =20 static void yt921x_poll_mib(struct work_struct *work) @@ -768,6 +771,7 @@ yt921x_dsa_get_ethtool_stats(struct dsa_switch *ds, int= port, uint64_t *data) yt921x_read_mib(priv, port); mutex_unlock(&priv->reg_lock); =20 + spin_lock(&pp->stats_lock); j =3D 0; for (size_t i =3D 0; i < ARRAY_SIZE(yt921x_mib_descs); i++) { const struct yt921x_mib_desc *desc =3D &yt921x_mib_descs[i]; @@ -778,6 +782,7 @@ yt921x_dsa_get_ethtool_stats(struct dsa_switch *ds, int= port, uint64_t *data) data[j] =3D ((u64 *)mib)[i]; j++; } + spin_unlock(&pp->stats_lock); } =20 static int yt921x_dsa_get_sset_count(struct dsa_switch *ds, int port, int = sset) @@ -809,6 +814,7 @@ yt921x_dsa_get_eth_mac_stats(struct dsa_switch *ds, int= port, yt921x_read_mib(priv, port); mutex_unlock(&priv->reg_lock); =20 + spin_lock(&pp->stats_lock); mac_stats->FramesTransmittedOK =3D pp->tx_frames; mac_stats->SingleCollisionFrames =3D mib->tx_single_collisions; mac_stats->MultipleCollisionFrames =3D mib->tx_multiple_collisions; @@ -831,6 +837,7 @@ yt921x_dsa_get_eth_mac_stats(struct dsa_switch *ds, int= port, /* mac_stats->InRangeLengthErrors */ /* mac_stats->OutOfRangeLengthField */ mac_stats->FrameTooLongErrors =3D mib->rx_oversize_errors; + spin_unlock(&pp->stats_lock); } =20 static void @@ -845,9 +852,11 @@ yt921x_dsa_get_eth_ctrl_stats(struct dsa_switch *ds, i= nt port, yt921x_read_mib(priv, port); mutex_unlock(&priv->reg_lock); =20 + spin_lock(&pp->stats_lock); ctrl_stats->MACControlFramesTransmitted =3D mib->tx_pause; ctrl_stats->MACControlFramesReceived =3D mib->rx_pause; /* ctrl_stats->UnsupportedOpcodesReceived */ + spin_unlock(&pp->stats_lock); } =20 static const struct ethtool_rmon_hist_range yt921x_rmon_ranges[] =3D { @@ -876,6 +885,8 @@ yt921x_dsa_get_rmon_stats(struct dsa_switch *ds, int po= rt, =20 *ranges =3D yt921x_rmon_ranges; =20 + spin_lock(&pp->stats_lock); + rmon_stats->undersize_pkts =3D mib->rx_undersize_errors; rmon_stats->oversize_pkts =3D mib->rx_oversize_errors; rmon_stats->fragments =3D mib->rx_alignment_errors; @@ -896,6 +907,8 @@ yt921x_dsa_get_rmon_stats(struct dsa_switch *ds, int po= rt, rmon_stats->hist_tx[4] =3D mib->tx_512_1023byte; rmon_stats->hist_tx[5] =3D mib->tx_1024_1518byte; rmon_stats->hist_tx[6] =3D mib->tx_jumbo; + + spin_unlock(&pp->stats_lock); } =20 static void @@ -906,6 +919,8 @@ yt921x_dsa_get_stats64(struct dsa_switch *ds, int port, struct yt921x_port *pp =3D &priv->ports[port]; struct yt921x_mib *mib =3D &pp->mib; =20 + spin_lock(&pp->stats_lock); + stats->rx_length_errors =3D mib->rx_undersize_errors + mib->rx_fragment_errors; stats->rx_over_errors =3D mib->rx_oversize_errors; @@ -932,6 +947,8 @@ yt921x_dsa_get_stats64(struct dsa_switch *ds, int port, /* stats->tx_dropped */ stats->multicast =3D mib->rx_multicast; stats->collisions =3D mib->tx_collisions; + + spin_unlock(&pp->stats_lock); } =20 static void @@ -946,8 +963,10 @@ yt921x_dsa_get_pause_stats(struct dsa_switch *ds, int = port, yt921x_read_mib(priv, port); mutex_unlock(&priv->reg_lock); =20 + spin_lock(&pp->stats_lock); pause_stats->tx_pause_frames =3D mib->tx_pause; pause_stats->rx_pause_frames =3D mib->rx_pause; + spin_unlock(&pp->stats_lock); } =20 static int diff --git a/drivers/net/dsa/yt921x.h b/drivers/net/dsa/yt921x.h index 61bb0ab3b09a..0c9d1b6cbc23 100644 --- a/drivers/net/dsa/yt921x.h +++ b/drivers/net/dsa/yt921x.h @@ -533,9 +533,14 @@ struct yt921x_port { bool isolated; =20 struct delayed_work mib_read; + /* protect the access to mib, rx_frames and tx_frames */ + spinlock_t stats_lock; struct yt921x_mib mib; u64 rx_frames; u64 tx_frames; + + /* only used by read routine to avoid huge allocations on the stack */ + struct yt921x_mib mib_new; }; =20 struct yt921x_reg_ops { --=20 2.51.0