From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pidgin.makrotopia.org (pidgin.makrotopia.org [185.142.180.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 84F96231A21; Sat, 2 May 2026 11:12:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.142.180.65 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777720326; cv=none; b=PwWnWOqG/HRM1yNwTHUNsWZieq1sVzLh+6Dhs6fcgFK+oEzaQPafURv9ZtwR9QyY0L5HY+eVQ6w+QXMhfOgXsJNDIGR0HCPadozYURA6DfAcJGrlD2eIZMnupirkOeb1L0vGxGb3oDgzchCM47wjF7yVjpGoegdUWN3T7cc8SDE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777720326; c=relaxed/simple; bh=6xd8XYBBRfH34GmxNLjSoqN0+MDrhUKk2oqtQc0jTog=; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=aVlkaiCvHy9DcxCbw4++53b8d7Yzj1urX0h5TPOU0EtzGbe+ko6v6cDXMH200z/xFELH9royKbqkBvQcBK+FeuRfGnN3zUCFlW784dCxvSrIE9wJe2m5vUOqK+f1V1EHoqSGr1Hhop1+e/zAf5l7lkU+VboiNnJRiBzoUpGCK/k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=makrotopia.org; spf=pass smtp.mailfrom=makrotopia.org; arc=none smtp.client-ip=185.142.180.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=makrotopia.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=makrotopia.org Received: from local by pidgin.makrotopia.org with esmtpsa (TLS1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.99) (envelope-from ) id 1wJ80C-000000007J3-2knb; Sat, 02 May 2026 10:55:16 +0000 Date: Sat, 2 May 2026 11:55:02 +0100 From: Daniel Golle To: "Chester A. Unal" , Daniel Golle , Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Matthias Brugger , AngeloGioacchino Del Regno , Russell King , Christian Marangi , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org Subject: [PATCH net v6] net: dsa: mt7530: fix .get_stats64 sleeping in atomic context Message-ID: <6940b913da2c29156f0feff74b678d3c526ee84c.1777719253.git.daniel@makrotopia.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline The .get_stats64 callback runs in atomic context, but on MDIO-connected switches every register read acquires the MDIO bus mutex, which can sleep: [ 12.645973] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:609 [ 12.654442] in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 759, name: grep [ 12.663377] preempt_count: 0, expected: 0 [ 12.667410] RCU nest depth: 1, expected: 0 [ 12.671511] INFO: lockdep is turned off. [ 12.675441] CPU: 0 UID: 0 PID: 759 Comm: grep Tainted: G S W 7.0.0+ #0 PREEMPT [ 12.675453] Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN [ 12.675456] Hardware name: Bananapi BPI-R64 (DT) [ 12.675459] Call trace: [ 12.675462] show_stack+0x14/0x1c (C) [ 12.675477] dump_stack_lvl+0x68/0x8c [ 12.675487] dump_stack+0x14/0x1c [ 12.675495] __might_resched+0x14c/0x220 [ 12.675504] __might_sleep+0x44/0x80 [ 12.675511] __mutex_lock+0x50/0xb10 [ 12.675523] mutex_lock_nested+0x20/0x30 [ 12.675532] mt7530_get_stats64+0x40/0x2ac [ 12.675542] dsa_user_get_stats64+0x2c/0x40 [ 12.675553] dev_get_stats+0x44/0x1e0 [ 12.675564] dev_seq_printf_stats+0x24/0xe0 [ 12.675575] dev_seq_show+0x14/0x3c [ 12.675583] seq_read_iter+0x37c/0x480 [ 12.675595] seq_read+0xd0/0xec [ 12.675605] proc_reg_read+0x94/0xe4 [ 12.675615] vfs_read+0x98/0x29c [ 12.675625] ksys_read+0x54/0xdc [ 12.675633] __arm64_sys_read+0x18/0x20 [ 12.675642] invoke_syscall.constprop.0+0x54/0xec [ 12.675653] do_el0_svc+0x3c/0xb4 [ 12.675662] el0_svc+0x38/0x200 [ 12.675670] el0t_64_sync_handler+0x98/0xdc [ 12.675679] el0t_64_sync+0x158/0x15c For MDIO-connected switches, poll MIB counters asynchronously using a delayed workqueue every second and let .get_stats64 return the cached values under a spinlock. A mod_delayed_work() call on each read triggers an immediate refresh so counters stay responsive when queried more frequently. MMIO-connected switches (MT7988, EN7581, AN7583) are not affected because their regmap does not sleep, so they continue to read MIB counters directly in .get_stats64. Fixes: 88c810f35ed5 ("net: dsa: mt7530: implement .get_stats64") Signed-off-by: Daniel Golle Acked-by: Chester A. Unal Reviewed-by: Andrew Lunn --- v6: * reintroduce .teardown() for cancel_delayed_work_sync(), drop cancel_delayed_work_sync() from .remove() v5: * spin_lock_init() and INIT_DELAYED_WORK() in probe() * drop teardown as cancel_delayed_work_sync() in remove() is sufficient and now symmetric with init happening in probe() v4: * extract mt7530_stats_refresh() helper from mt7530_stats_poll() -> mt7530_stats_poll() now just refreshes and re-arms * call helper synchronously in mt753x_setup() to seed the cache * avoid zeroed counters during the first poll interval * avoid INITIAL_JIFFIES vs stats_last==0 wraparound on 32-bit * swap deprecated system_wq for system_percpu_wq in get_stats64 * keeps on-demand refresh on the same queue as schedule_*_work v3: * move `stats_last` access under the spinlock to avoid potential race v2: * use spin_lock_bh()/spin_unlock_bh() to prevent potential deadlock * rate-limit mod_delayed_work() refresh to at most once per 100ms * move cancel_delayed_work_sync() after dsa_unregister_switch() * add mt753x_teardown() callback to cancel the stats work * fix commit message drivers/net/dsa/mt7530.c | 75 ++++++++++++++++++++++++++++++++++++++-- drivers/net/dsa/mt7530.h | 8 +++++ 2 files changed, 80 insertions(+), 3 deletions(-) diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c index b9423389c2ef..44d670904ad8 100644 --- a/drivers/net/dsa/mt7530.c +++ b/drivers/net/dsa/mt7530.c @@ -25,6 +25,9 @@ #include "mt7530.h" +#define MT7530_STATS_POLL_INTERVAL (1 * HZ) +#define MT7530_STATS_RATE_LIMIT (HZ / 10) + static struct mt753x_pcs *pcs_to_mt753x_pcs(struct phylink_pcs *pcs) { return container_of(pcs, struct mt753x_pcs, pcs); @@ -906,10 +909,9 @@ static void mt7530_get_rmon_stats(struct dsa_switch *ds, int port, *ranges = mt7530_rmon_ranges; } -static void mt7530_get_stats64(struct dsa_switch *ds, int port, - struct rtnl_link_stats64 *storage) +static void mt7530_read_port_stats64(struct mt7530_priv *priv, int port, + struct rtnl_link_stats64 *storage) { - struct mt7530_priv *priv = ds->priv; uint64_t data; /* MIB counter doesn't provide a FramesTransmittedOK but instead @@ -951,6 +953,54 @@ static void mt7530_get_stats64(struct dsa_switch *ds, int port, &storage->rx_crc_errors); } +static void mt7530_stats_refresh(struct mt7530_priv *priv) +{ + struct rtnl_link_stats64 stats = {}; + struct dsa_port *dp; + int port; + + dsa_switch_for_each_user_port(dp, priv->ds) { + port = dp->index; + + mt7530_read_port_stats64(priv, port, &stats); + + spin_lock_bh(&priv->stats_lock); + priv->ports[port].stats = stats; + priv->stats_last = jiffies; + spin_unlock_bh(&priv->stats_lock); + } +} + +static void mt7530_stats_poll(struct work_struct *work) +{ + struct mt7530_priv *priv = container_of(work, struct mt7530_priv, + stats_work.work); + + mt7530_stats_refresh(priv); + schedule_delayed_work(&priv->stats_work, + MT7530_STATS_POLL_INTERVAL); +} + +static void mt7530_get_stats64(struct dsa_switch *ds, int port, + struct rtnl_link_stats64 *storage) +{ + struct mt7530_priv *priv = ds->priv; + bool refresh; + + if (priv->bus) { + spin_lock_bh(&priv->stats_lock); + *storage = priv->ports[port].stats; + refresh = time_after(jiffies, priv->stats_last + + MT7530_STATS_RATE_LIMIT); + spin_unlock_bh(&priv->stats_lock); + if (refresh) + mod_delayed_work(system_percpu_wq, + &priv->stats_work, 0); + } else { + mt7530_read_port_stats64(priv, port, storage); + } +} + static void mt7530_get_eth_ctrl_stats(struct dsa_switch *ds, int port, struct ethtool_eth_ctrl_stats *ctrl_stats) { @@ -3137,9 +3187,24 @@ mt753x_setup(struct dsa_switch *ds) if (ret && priv->irq_domain) mt7530_free_mdio_irq(priv); + if (!ret && priv->bus) { + mt7530_stats_refresh(priv); + schedule_delayed_work(&priv->stats_work, + MT7530_STATS_POLL_INTERVAL); + } + return ret; } +static void +mt753x_teardown(struct dsa_switch *ds) +{ + struct mt7530_priv *priv = ds->priv; + + if (priv->bus) + cancel_delayed_work_sync(&priv->stats_work); +} + static int mt753x_set_mac_eee(struct dsa_switch *ds, int port, struct ethtool_keee *e) { @@ -3257,6 +3322,7 @@ static int mt7988_setup(struct dsa_switch *ds) static const struct dsa_switch_ops mt7530_switch_ops = { .get_tag_protocol = mtk_get_tag_protocol, .setup = mt753x_setup, + .teardown = mt753x_teardown, .preferred_default_local_cpu_port = mt753x_preferred_default_local_cpu_port, .get_strings = mt7530_get_strings, .get_ethtool_stats = mt7530_get_ethtool_stats, @@ -3395,6 +3461,9 @@ mt7530_probe_common(struct mt7530_priv *priv) priv->ds->ops = &mt7530_switch_ops; priv->ds->phylink_mac_ops = &mt753x_phylink_mac_ops; mutex_init(&priv->reg_mutex); + spin_lock_init(&priv->stats_lock); + INIT_DELAYED_WORK(&priv->stats_work, mt7530_stats_poll); + dev_set_drvdata(dev, priv); return 0; diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h index 3e0090bed298..dd33b0df3419 100644 --- a/drivers/net/dsa/mt7530.h +++ b/drivers/net/dsa/mt7530.h @@ -796,6 +796,7 @@ struct mt7530_fdb { * @pvid: The VLAN specified is to be considered a PVID at ingress. Any * untagged frames will be assigned to the related VLAN. * @sgmii_pcs: Pointer to PCS instance for SerDes ports + * @stats: Cached port statistics for MDIO-connected switches */ struct mt7530_port { bool enable; @@ -803,6 +804,7 @@ struct mt7530_port { u32 pm; u16 pvid; struct phylink_pcs *sgmii_pcs; + struct rtnl_link_stats64 stats; }; /* Port 5 mode definitions of the MT7530 switch */ @@ -875,6 +877,9 @@ struct mt753x_info { * @create_sgmii: Pointer to function creating SGMII PCS instance(s) * @active_cpu_ports: Holding the active CPU ports * @mdiodev: The pointer to the MDIO device structure + * @stats_lock: Protects cached per-port stats from concurrent access + * @stats_work: Delayed work for polling MIB counters on MDIO switches + * @stats_last: Jiffies timestamp of last MIB counter poll */ struct mt7530_priv { struct device *dev; @@ -900,6 +905,9 @@ struct mt7530_priv { int (*create_sgmii)(struct mt7530_priv *priv); u8 active_cpu_ports; struct mdio_device *mdiodev; + spinlock_t stats_lock; /* protects cached stats counters */ + struct delayed_work stats_work; + unsigned long stats_last; }; struct mt7530_hw_vlan_entry { -- 2.53.0