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Message-ID: <20250115035319.559603-9-kuba@kernel.org>
Date: Tue, 14 Jan 2025 19:53:16 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
edumazet@...gle.com,
pabeni@...hat.com,
andrew+netdev@...n.ch,
horms@...nel.org,
jdamato@...tly.com,
Jakub Kicinski <kuba@...nel.org>,
leitao@...ian.org
Subject: [PATCH net-next v2 08/11] net: protect threaded status of NAPI with netdev_lock()
Now that NAPI instances can't come and go without holding
netdev->lock we can trivially switch from rtnl_lock() to
netdev_lock() for setting netdev->threaded via sysfs.
Note that since we do not lock netdev_lock around sysfs
calls in the core we don't have to "trylock" like we do
with rtnl_lock.
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
v2:
- update the comment on dev_isalive()
v1: https://lore.kernel.org/20250114035118.110297-9-kuba@kernel.org
CC: leitao@...ian.org
---
include/linux/netdevice.h | 13 +++++++++++--
net/core/dev.c | 2 ++
net/core/net-sysfs.c | 34 ++++++++++++++++++++++++++++++++--
3 files changed, 45 insertions(+), 4 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4ab33fbadd9f..bf3da95c9350 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -384,7 +384,7 @@ struct napi_struct {
int rx_count; /* length of rx_list */
unsigned int napi_id; /* protected by netdev_lock */
struct hrtimer timer;
- struct task_struct *thread;
+ struct task_struct *thread; /* protected by netdev_lock */
unsigned long gro_flush_timeout;
unsigned long irq_suspend_timeout;
u32 defer_hard_irqs;
@@ -2451,11 +2451,13 @@ struct net_device {
* Drivers are free to use it for other protection.
*
* Protects:
- * @napi_list, @net_shaper_hierarchy, @reg_state
+ * @napi_list, @net_shaper_hierarchy, @reg_state, @threaded
*
* Partially protects (writers must hold both @lock and rtnl_lock):
* @up
*
+ * Also protects some fields in struct napi_struct.
+ *
* Ordering: take after rtnl_lock.
*/
struct mutex lock;
@@ -2697,6 +2699,13 @@ static inline void netdev_assert_locked(struct net_device *dev)
lockdep_assert_held(&dev->lock);
}
+static inline void netdev_assert_locked_or_invisible(struct net_device *dev)
+{
+ if (dev->reg_state == NETREG_REGISTERED ||
+ dev->reg_state == NETREG_UNREGISTERING)
+ netdev_assert_locked(dev);
+}
+
static inline void netif_napi_set_irq(struct napi_struct *napi, int irq)
{
napi->irq = irq;
diff --git a/net/core/dev.c b/net/core/dev.c
index 9734c3f5b862..d90bb100285d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6784,6 +6784,8 @@ int dev_set_threaded(struct net_device *dev, bool threaded)
struct napi_struct *napi;
int err = 0;
+ netdev_assert_locked_or_invisible(dev);
+
if (dev->threaded == threaded)
return 0;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 2d9afc6e2161..9365a7185a1d 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -36,7 +36,7 @@ static const char fmt_uint[] = "%u\n";
static const char fmt_ulong[] = "%lu\n";
static const char fmt_u64[] = "%llu\n";
-/* Caller holds RTNL or RCU */
+/* Caller holds RTNL, netdev->lock or RCU */
static inline int dev_isalive(const struct net_device *dev)
{
return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
@@ -108,6 +108,36 @@ static ssize_t netdev_store(struct device *dev, struct device_attribute *attr,
return ret;
}
+/* Same as netdev_store() but takes netdev_lock() instead of rtnl_lock() */
+static ssize_t
+netdev_lock_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t len,
+ int (*set)(struct net_device *, unsigned long))
+{
+ struct net_device *netdev = to_net_dev(dev);
+ struct net *net = dev_net(netdev);
+ unsigned long new;
+ int ret;
+
+ if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+ return -EPERM;
+
+ ret = kstrtoul(buf, 0, &new);
+ if (ret)
+ return ret;
+
+ netdev_lock(netdev);
+
+ if (dev_isalive(netdev)) {
+ ret = (*set)(netdev, new);
+ if (ret == 0)
+ ret = len;
+ }
+ netdev_unlock(netdev);
+
+ return ret;
+}
+
NETDEVICE_SHOW_RO(dev_id, fmt_hex);
NETDEVICE_SHOW_RO(dev_port, fmt_dec);
NETDEVICE_SHOW_RO(addr_assign_type, fmt_dec);
@@ -638,7 +668,7 @@ static ssize_t threaded_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t len)
{
- return netdev_store(dev, attr, buf, len, modify_napi_threaded);
+ return netdev_lock_store(dev, attr, buf, len, modify_napi_threaded);
}
static DEVICE_ATTR_RW(threaded);
--
2.48.0
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