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Message-Id: <20251104221348.4163417-2-florian.fainelli@broadcom.com>
Date: Tue, 4 Nov 2025 14:13:47 -0800
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: netdev@...r.kernel.org
Cc: bcm-kernel-feedback-list@...adcom.com,
Florian Fainelli <florian.fainelli@...adcom.com>,
Doug Berger <opendmb@...il.com>,
Andrew Lunn <andrew+netdev@...n.ch>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>,
Stanislav Fomichev <sdf@...ichev.me>,
Antoine Tenart <atenart@...nel.org>,
Kuniyuki Iwashima <kuniyu@...gle.com>,
Yajun Deng <yajun.deng@...ux.dev>,
linux-kernel@...r.kernel.org (open list)
Subject: [PATCH net-next v2 1/2] net: ethernet: Allow disabling pause on panic
Development devices on a lab network might be subject to kernel panics
and if they have pause frame generation enabled, once the kernel panics,
the Ethernet controller stops being serviced. This can create a flood of
pause frames that certain switches are unable to handle resulting a
completle paralysis of the network because they broadcast to other
stations on that same network segment.
To accomodate for such situation introduce a
/sys/class/net/<device>/disable_pause_on_panic knob which will disable
Ethernet pause frame generation upon kernel panic.
Note that device driver wishing to make use of that feature need to
implement ethtool_ops::set_pauseparam_panic to specifically deal with
that atomic context.
Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
---
Documentation/ABI/testing/sysfs-class-net | 16 +++++
include/linux/ethtool.h | 3 +
include/linux/netdevice.h | 1 +
net/core/net-sysfs.c | 34 ++++++++++
net/ethernet/Makefile | 3 +-
net/ethernet/pause_panic.c | 81 +++++++++++++++++++++++
6 files changed, 137 insertions(+), 1 deletion(-)
create mode 100644 net/ethernet/pause_panic.c
diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
index ebf21beba846..f762ce439203 100644
--- a/Documentation/ABI/testing/sysfs-class-net
+++ b/Documentation/ABI/testing/sysfs-class-net
@@ -352,3 +352,19 @@ Description:
0 threaded mode disabled for this dev
1 threaded mode enabled for this dev
== ==================================
+
+What: /sys/class/net/<iface>/disable_pause_on_panic
+Date: Nov 2025
+KernelVersion: 6.20
+Contact: netdev@...r.kernel.org
+Description:
+ Boolean value to control whether to disable pause frame
+ generation on panic. This is helpful in environments where
+ the link partner may incorrect respond to pause frames (e.g.:
+ improperly configured Ethernet switches)
+
+ Possible values:
+ == ==================================
+ 0 threaded mode disabled for this dev
+ 1 threaded mode enabled for this dev
+ == ==================================
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index c2d8b4ec62eb..e014d0f2a5ac 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -956,6 +956,8 @@ struct kernel_ethtool_ts_info {
* @get_pauseparam: Report pause parameters
* @set_pauseparam: Set pause parameters. Returns a negative error code
* or zero.
+ * @set_pauseparam_panic: Set pause parameters while in a panic context. This
+ * call is not allowed to sleep. Returns a negative error code or zero.
* @self_test: Run specified self-tests
* @get_strings: Return a set of strings that describe the requested objects
* @set_phys_id: Identify the physical devices, e.g. by flashing an LED
@@ -1170,6 +1172,7 @@ struct ethtool_ops {
struct ethtool_pauseparam*);
int (*set_pauseparam)(struct net_device *,
struct ethtool_pauseparam*);
+ void (*set_pauseparam_panic)(struct net_device *);
void (*self_test)(struct net_device *, struct ethtool_test *, u64 *);
void (*get_strings)(struct net_device *, u32 stringset, u8 *);
int (*set_phys_id)(struct net_device *, enum ethtool_phys_id_state);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e808071dbb7d..2d4b07693745 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2441,6 +2441,7 @@ struct net_device {
bool proto_down;
bool irq_affinity_auto;
bool rx_cpu_rmap_auto;
+ bool disable_pause_on_panic;
/* priv_flags_slow, ungrouped to save space */
unsigned long see_all_hwtstamp_requests:1;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index ca878525ad7c..c01dc3e200d8 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -770,6 +770,39 @@ static ssize_t threaded_store(struct device *dev,
}
static DEVICE_ATTR_RW(threaded);
+static ssize_t disable_pause_on_panic_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct net_device *ndev = to_net_dev(dev);
+ ssize_t ret = -EINVAL;
+
+ rcu_read_lock();
+ if (dev_isalive(ndev))
+ ret = sysfs_emit(buf, fmt_dec, READ_ONCE(ndev->disable_pause_on_panic));
+ rcu_read_unlock();
+
+ return ret;
+}
+
+static int modify_disable_pause_on_panic(struct net_device *dev, unsigned long val)
+{
+ if (val != 0 && val != 1)
+ return -EINVAL;
+
+ WRITE_ONCE(dev->disable_pause_on_panic, val);
+
+ return 0;
+}
+
+static ssize_t disable_pause_on_panic_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ return netdev_store(dev, attr, buf, len, modify_disable_pause_on_panic);
+}
+static DEVICE_ATTR_RW(disable_pause_on_panic);
+
static struct attribute *net_class_attrs[] __ro_after_init = {
&dev_attr_netdev_group.attr,
&dev_attr_type.attr,
@@ -800,6 +833,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
&dev_attr_carrier_up_count.attr,
&dev_attr_carrier_down_count.attr,
&dev_attr_threaded.attr,
+ &dev_attr_disable_pause_on_panic.attr,
NULL,
};
ATTRIBUTE_GROUPS(net_class);
diff --git a/net/ethernet/Makefile b/net/ethernet/Makefile
index e03eff94e0db..9b1f3ff8695a 100644
--- a/net/ethernet/Makefile
+++ b/net/ethernet/Makefile
@@ -3,4 +3,5 @@
# Makefile for the Linux Ethernet layer.
#
-obj-y += eth.o
+obj-y += eth.o \
+ pause_panic.o
diff --git a/net/ethernet/pause_panic.c b/net/ethernet/pause_panic.c
new file mode 100644
index 000000000000..8ef61eb768a0
--- /dev/null
+++ b/net/ethernet/pause_panic.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ethernet pause disable on panic handler
+ *
+ * This module provides per-device control via sysfs to disable Ethernet flow
+ * control (pause frames) on individual Ethernet devices when the kernel panics.
+ * Each device can be configured via /sys/class/net/<device>/disable_pause_on_panic.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/panic_notifier.h>
+#include <linux/netdevice.h>
+#include <linux/ethtool.h>
+#include <linux/notifier.h>
+#include <linux/if_ether.h>
+#include <net/net_namespace.h>
+
+/*
+ * Disable pause/flow control on a single Ethernet device.
+ */
+static void disable_pause_on_device(struct net_device *dev)
+{
+ const struct ethtool_ops *ops;
+
+ /* Only proceed if this device has the flag enabled */
+ if (!READ_ONCE(dev->disable_pause_on_panic))
+ return;
+
+ ops = dev->ethtool_ops;
+ if (!ops || !ops->set_pauseparam_panic)
+ return;
+
+ /*
+ * In panic context, we're in atomic context and cannot sleep.
+ */
+ ops->set_pauseparam_panic(dev);
+}
+
+/*
+ * Panic notifier to disable pause frames on all Ethernet devices.
+ * Called in atomic context during kernel panic.
+ */
+static int eth_pause_panic_handler(struct notifier_block *this,
+ unsigned long event, void *ptr)
+{
+ struct net_device *dev;
+
+ /*
+ * Iterate over all network devices in the init namespace.
+ * In panic context, we cannot acquire locks that might sleep,
+ * so we use RCU iteration.
+ * Each device will check its own disable_pause_on_panic flag.
+ */
+ rcu_read_lock();
+ for_each_netdev_rcu(&init_net, dev) {
+ /* Reference count might not be available in panic */
+ if (!dev)
+ continue;
+
+ disable_pause_on_device(dev);
+ }
+ rcu_read_unlock();
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block eth_pause_panic_notifier = {
+ .notifier_call = eth_pause_panic_handler,
+ .priority = INT_MAX, /* Run as late as possible */
+};
+
+static int __init eth_pause_panic_init(void)
+{
+ /* Register panic notifier */
+ atomic_notifier_chain_register(&panic_notifier_list,
+ ð_pause_panic_notifier);
+
+ return 0;
+}
+device_initcall(eth_pause_panic_init);
--
2.34.1
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