From: David Yang <mmyangfl@gmail.com>
To: netdev@vger.kernel.org
Cc: David Yang <mmyangfl@gmail.com>, Andrew Lunn <andrew@lunn.ch>,
Vladimir Oltean <olteanv@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Russell King <linux@armlinux.org.uk>,
linux-kernel@vger.kernel.org
Subject: [PATCH net-next v2 5/6] net: dsa: motorcomm: Fix MIB synchronization
Date: Sat, 5 Sep 2026 00:29:47 +0800 [thread overview]
Message-ID: <20260904162952.709368-6-mmyangfl@gmail.com> (raw)
In-Reply-To: <20260904162952.709368-1-mmyangfl@gmail.com>
The previous MIB sync was based on the false assumption that 64-bit
variables are always atomic. To fix that:
* .get_stats64() uses u64_stats_sync, together with u64_stats_t;
* others take the free mutex lock if possible.
To minimize time of the write side of u64_stats_sync, a per-port buffer
is used so that all the stat can be written back altogether after IO
operations.
Signed-off-by: David Yang <mmyangfl@gmail.com>
---
drivers/net/dsa/motorcomm/chip.c | 2 +
drivers/net/dsa/motorcomm/mib.c | 90 +++++++++++++++++++-------------
drivers/net/dsa/motorcomm/mib.h | 6 +++
3 files changed, 63 insertions(+), 35 deletions(-)
diff --git a/drivers/net/dsa/motorcomm/chip.c b/drivers/net/dsa/motorcomm/chip.c
index d8520c38f9c7..b4059053ef15 100644
--- a/drivers/net/dsa/motorcomm/chip.c
+++ b/drivers/net/dsa/motorcomm/chip.c
@@ -19,6 +19,7 @@
#include <linux/of_mdio.h>
#include <linux/of_net.h>
#include <linux/sort.h>
+#include <linux/u64_stats_sync.h>
#include <net/dsa.h>
#include <net/dscp.h>
@@ -3778,6 +3779,7 @@ static int yt921x_dsa_port_setup(struct dsa_switch *ds, int port)
pp->mib = pm;
pm->port = pp;
+ u64_stats_init(&pm->syncp);
INIT_DELAYED_WORK(&pm->work, yt921x_mib_poll);
}
diff --git a/drivers/net/dsa/motorcomm/mib.c b/drivers/net/dsa/motorcomm/mib.c
index d8a564d83bad..31d86c3122c7 100644
--- a/drivers/net/dsa/motorcomm/mib.c
+++ b/drivers/net/dsa/motorcomm/mib.c
@@ -92,6 +92,7 @@ static int yt921x_mib_read(struct yt921x_priv *priv, int port)
struct device *dev = to_device(priv);
struct yt921x_mib *pm = pp->mib;
struct yt921x_mib_stats *mib;
+ u64 *buf = pm->data;
u64 rx_frames;
u64 tx_frames;
int res = 0;
@@ -101,7 +102,6 @@ static int yt921x_mib_read(struct yt921x_priv *priv, int port)
for (size_t i = 0; i < ARRAY_SIZE(yt921x_mib_descs); i++) {
const struct yt921x_mib_desc *desc = &yt921x_mib_descs[i];
u32 reg = YT921X_MIBn_DATA0(port) + desc->offset;
- u64_stats_t *valp = &((u64_stats_t *)mib)[i];
u32 val0;
u64 val;
@@ -110,7 +110,7 @@ static int yt921x_mib_read(struct yt921x_priv *priv, int port)
break;
if (desc->size <= 1) {
- u64 old_val = u64_stats_read(valp);
+ u64 old_val = buf[i];
val = (old_val & ~(u64)U32_MAX) | val0;
if (val < old_val)
@@ -124,9 +124,12 @@ static int yt921x_mib_read(struct yt921x_priv *priv, int port)
val = ((u64)val1 << 32) | val0;
}
- u64_stats_set(valp, val);
+ buf[i] = val;
}
+ u64_stats_update_begin(&pm->syncp);
+ for (size_t i = 0; i < ARRAY_SIZE(yt921x_mib_descs); i++)
+ u64_stats_set(&((u64_stats_t *)mib)[i], buf[i]);
rx_frames = u64_stats_read(&mib->rx_64byte) +
u64_stats_read(&mib->rx_65_127byte) +
u64_stats_read(&mib->rx_128_255byte) +
@@ -143,6 +146,7 @@ static int yt921x_mib_read(struct yt921x_priv *priv, int port)
u64_stats_read(&mib->tx_jumbo);
u64_stats_set(&pm->rx_frames, rx_frames);
u64_stats_set(&pm->tx_frames, tx_frames);
+ u64_stats_update_end(&pm->syncp);
if (res)
dev_err(dev, "Failed to %s port %d: %i\n", "read stats for",
@@ -191,16 +195,16 @@ yt921x_dsa_get_ethtool_stats(struct dsa_switch *ds, int port, uint64_t *data)
struct yt921x_priv *priv = to_yt921x_priv(ds);
struct yt921x_port *pp = &priv->ports[port];
struct yt921x_mib *pm = pp->mib;
- struct yt921x_mib_stats *mib;
+ u64 *buf;
size_t j;
if (!pm)
return;
- mib = &pm->stats;
+ buf = pm->data;
mutex_lock(&priv->reg_lock);
+
yt921x_mib_read(priv, port);
- mutex_unlock(&priv->reg_lock);
j = 0;
for (size_t i = 0; i < ARRAY_SIZE(yt921x_mib_descs); i++) {
@@ -209,9 +213,11 @@ yt921x_dsa_get_ethtool_stats(struct dsa_switch *ds, int port, uint64_t *data)
if (!desc->name)
continue;
- data[j] = u64_stats_read(&((u64_stats_t *)mib)[i]);
+ data[j] = buf[i];
j++;
}
+
+ mutex_unlock(&priv->reg_lock);
}
int yt921x_dsa_get_sset_count(struct dsa_switch *ds, int port, int sset)
@@ -245,8 +251,8 @@ yt921x_dsa_get_eth_mac_stats(struct dsa_switch *ds, int port,
mib = &pm->stats;
mutex_lock(&priv->reg_lock);
+
yt921x_mib_read(priv, port);
- mutex_unlock(&priv->reg_lock);
mac_stats->FramesTransmittedOK = u64_stats_read(&pm->tx_frames);
mac_stats->SingleCollisionFrames = u64_stats_read(&mib->tx_single_collisions);
@@ -270,6 +276,8 @@ yt921x_dsa_get_eth_mac_stats(struct dsa_switch *ds, int port,
/* mac_stats->InRangeLengthErrors */
/* mac_stats->OutOfRangeLengthField */
mac_stats->FrameTooLongErrors = u64_stats_read(&mib->rx_oversize_errors);
+
+ mutex_unlock(&priv->reg_lock);
}
void
@@ -286,12 +294,14 @@ yt921x_dsa_get_eth_ctrl_stats(struct dsa_switch *ds, int port,
mib = &pm->stats;
mutex_lock(&priv->reg_lock);
+
yt921x_mib_read(priv, port);
- mutex_unlock(&priv->reg_lock);
ctrl_stats->MACControlFramesTransmitted = u64_stats_read(&mib->tx_pause);
ctrl_stats->MACControlFramesReceived = u64_stats_read(&mib->rx_pause);
/* ctrl_stats->UnsupportedOpcodesReceived */
+
+ mutex_unlock(&priv->reg_lock);
}
const struct ethtool_rmon_hist_range yt921x_rmon_ranges[] = {
@@ -320,8 +330,8 @@ yt921x_dsa_get_rmon_stats(struct dsa_switch *ds, int port,
mib = &pm->stats;
mutex_lock(&priv->reg_lock);
+
yt921x_mib_read(priv, port);
- mutex_unlock(&priv->reg_lock);
*ranges = yt921x_rmon_ranges;
@@ -345,6 +355,8 @@ yt921x_dsa_get_rmon_stats(struct dsa_switch *ds, int port,
rmon_stats->hist_tx[4] = u64_stats_read(&mib->tx_512_1023byte);
rmon_stats->hist_tx[5] = u64_stats_read(&mib->tx_1024_1518byte);
rmon_stats->hist_tx[6] = u64_stats_read(&mib->tx_jumbo);
+
+ mutex_unlock(&priv->reg_lock);
}
void
@@ -355,39 +367,45 @@ yt921x_dsa_get_stats64(struct dsa_switch *ds, int port,
struct yt921x_port *pp = &priv->ports[port];
struct yt921x_mib *pm = pp->mib;
struct yt921x_mib_stats *mib;
+ unsigned int start;
if (!pm)
return;
mib = &pm->stats;
- stats->rx_length_errors = u64_stats_read(&mib->rx_undersize_errors) +
- u64_stats_read(&mib->rx_fragment_errors);
- stats->rx_over_errors = u64_stats_read(&mib->rx_oversize_errors);
- stats->rx_crc_errors = u64_stats_read(&mib->rx_crc_errors);
- stats->rx_frame_errors = u64_stats_read(&mib->rx_alignment_errors);
- /* stats->rx_fifo_errors */
- /* stats->rx_missed_errors */
-
- stats->tx_aborted_errors = u64_stats_read(&mib->tx_aborted_errors);
- /* stats->tx_carrier_errors */
- stats->tx_fifo_errors = u64_stats_read(&mib->tx_undersize_errors);
- /* stats->tx_heartbeat_errors */
- stats->tx_window_errors = u64_stats_read(&mib->tx_late_collisions);
-
- stats->rx_packets = u64_stats_read(&pm->rx_frames);
- stats->tx_packets = u64_stats_read(&pm->tx_frames);
- stats->rx_bytes = u64_stats_read(&mib->rx_good_bytes) -
- ETH_FCS_LEN * stats->rx_packets;
- stats->tx_bytes = u64_stats_read(&mib->tx_good_bytes) -
- ETH_FCS_LEN * stats->tx_packets;
+ do {
+ start = u64_stats_fetch_begin(&pm->syncp);
+
+ stats->rx_length_errors = u64_stats_read(&mib->rx_undersize_errors) +
+ u64_stats_read(&mib->rx_fragment_errors);
+ stats->rx_over_errors = u64_stats_read(&mib->rx_oversize_errors);
+ stats->rx_crc_errors = u64_stats_read(&mib->rx_crc_errors);
+ stats->rx_frame_errors = u64_stats_read(&mib->rx_alignment_errors);
+ /* stats->rx_fifo_errors */
+ /* stats->rx_missed_errors */
+
+ stats->tx_aborted_errors = u64_stats_read(&mib->tx_aborted_errors);
+ /* stats->tx_carrier_errors */
+ stats->tx_fifo_errors = u64_stats_read(&mib->tx_undersize_errors);
+ /* stats->tx_heartbeat_errors */
+ stats->tx_window_errors = u64_stats_read(&mib->tx_late_collisions);
+
+ stats->rx_packets = u64_stats_read(&pm->rx_frames);
+ stats->tx_packets = u64_stats_read(&pm->tx_frames);
+ stats->rx_bytes = u64_stats_read(&mib->rx_good_bytes) -
+ ETH_FCS_LEN * stats->rx_packets;
+ stats->tx_bytes = u64_stats_read(&mib->tx_good_bytes) -
+ ETH_FCS_LEN * stats->tx_packets;
+ stats->rx_dropped = u64_stats_read(&mib->rx_dropped);
+ /* stats->tx_dropped */
+ stats->multicast = u64_stats_read(&mib->rx_multicast);
+ stats->collisions = u64_stats_read(&mib->tx_collisions);
+ } while (u64_stats_fetch_retry(&pm->syncp, start));
+
stats->rx_errors = stats->rx_length_errors + stats->rx_over_errors +
stats->rx_crc_errors + stats->rx_frame_errors;
stats->tx_errors = stats->tx_aborted_errors + stats->tx_fifo_errors +
stats->tx_window_errors;
- stats->rx_dropped = u64_stats_read(&mib->rx_dropped);
- /* stats->tx_dropped */
- stats->multicast = u64_stats_read(&mib->rx_multicast);
- stats->collisions = u64_stats_read(&mib->tx_collisions);
}
void
@@ -404,9 +422,11 @@ yt921x_dsa_get_pause_stats(struct dsa_switch *ds, int port,
mib = &pm->stats;
mutex_lock(&priv->reg_lock);
+
yt921x_mib_read(priv, port);
- mutex_unlock(&priv->reg_lock);
pause_stats->tx_pause_frames = u64_stats_read(&mib->tx_pause);
pause_stats->rx_pause_frames = u64_stats_read(&mib->rx_pause);
+
+ mutex_unlock(&priv->reg_lock);
}
diff --git a/drivers/net/dsa/motorcomm/mib.h b/drivers/net/dsa/motorcomm/mib.h
index d84ae2f449ac..33992a5f9bdc 100644
--- a/drivers/net/dsa/motorcomm/mib.h
+++ b/drivers/net/dsa/motorcomm/mib.h
@@ -125,13 +125,19 @@ struct yt921x_mib_stats {
u64_stats_t tx_oam;
};
+#define YT921X_MIB_NUM (sizeof(struct yt921x_mib_stats) / sizeof(u64_stats_t))
+
struct yt921x_mib {
struct yt921x_port *port;
struct delayed_work work;
+ struct u64_stats_sync syncp;
+ /* protected by syncp OR priv->reg_lock */
struct yt921x_mib_stats stats;
u64_stats_t rx_frames;
u64_stats_t tx_frames;
+ /* protected by priv->reg_lock */
+ u64 data[YT921X_MIB_NUM];
};
void yt921x_mib_poll(struct work_struct *work);
--
2.53.0
next prev parent reply other threads:[~2026-09-04 16:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 16:29 [PATCH net-next v2 0/6] net: dsa: motorcomm: MIB fixup David Yang
2026-09-04 16:29 ` [PATCH net-next v2 1/6] net: dsa: motorcomm: Rename MIB stuffs David Yang
2026-09-04 16:29 ` [PATCH net-next v2 2/6] net: dsa: motorcomm: Split MIB buffers David Yang
2026-09-04 16:29 ` [PATCH net-next v2 3/6] net: dsa: motorcomm: Split MIB module David Yang
2026-09-04 16:29 ` [PATCH net-next v2 4/6] net: dsa: motorcomm: Use u64_stats_t for MIB stats David Yang
2026-09-04 16:29 ` David Yang [this message]
2026-09-04 16:29 ` [PATCH net-next v2 6/6] net: dsa: motorcomm: Use safe 64-bit counter reader David Yang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260904162952.709368-6-mmyangfl@gmail.com \
--to=mmyangfl@gmail.com \
--cc=andrew@lunn.ch \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=netdev@vger.kernel.org \
--cc=olteanv@gmail.com \
--cc=pabeni@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox