[PATCH net-next v2 08/11] net: protect threaded status of NAPI with netdev_lock()
From: Jakub Kicinski <kuba@kernel.org>
Date: 2025-01-15 03:53:41
Subsystem:
networking drivers, networking [general], the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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@google.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org> --- v2: - update the comment on dev_isalive() v1: https://lore.kernel.org/20250114035118.110297-9-kuba@kernel.org (local) CC: leitao@debian.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