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Miller" , Jakub Kicinski , Paolo Abeni Cc: Kuniyuki Iwashima , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet X-Patchwork-Delegate: kuba@kernel.org With upcoming per netns RTNL, rtnl use in netdev_nl_napi_get_doit() is a bit problematic. Prepare netdev_nl_napi_fill_one() to not rely on RTNL: 1) netif_napi_set_irq() uses WRITE_ONCE(napi->irq, ...) 2) napi_kthread_create() uses WRITE_ONCE(napi->thread, ...) 3) Add napi->thread_pid_nr to avoid race in netdev_nl_napi_fill_one and __netif_napi_del() 4) netdev_nl_napi_fill_one() uses corresponding READ_ONCE() 5) netdev_nl_napi_get_doit() can use RCU instead of RTNL Signed-off-by: Eric Dumazet --- include/linux/netdevice.h | 3 ++- net/core/dev.c | 21 ++++++++++++--------- net/core/netdev-genl.c | 21 +++++++++++---------- 3 files changed, 25 insertions(+), 20 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 3baf8e539b6f33caaf83961c4cf619b799e5e41d..64a5e4927901740db8dbc255ed19faca96820333 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -377,6 +377,7 @@ struct napi_struct { struct list_head dev_list; struct hlist_node napi_hash_node; int irq; + pid_t thread_pid_nr; }; enum { @@ -2618,7 +2619,7 @@ void netif_queue_set_napi(struct net_device *dev, unsigned int queue_index, static inline void netif_napi_set_irq(struct napi_struct *napi, int irq) { - napi->irq = irq; + WRITE_ONCE(napi->irq, irq); } /* Default NAPI poll() weight diff --git a/net/core/dev.c b/net/core/dev.c index ea5fbcd133ae4c743545945def00790ec74e2bb6..77c39a95e74df2485777bc008a507bdcc4e75a00 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1423,21 +1423,23 @@ static int napi_threaded_poll(void *data); static int napi_kthread_create(struct napi_struct *n) { - int err = 0; + struct task_struct *thread; /* Create and wake up the kthread once to put it in * TASK_INTERRUPTIBLE mode to avoid the blocked task * warning and work with loadavg. */ - n->thread = kthread_run(napi_threaded_poll, n, "napi/%s-%d", + thread = kthread_run(napi_threaded_poll, n, "napi/%s-%d", n->dev->name, n->napi_id); - if (IS_ERR(n->thread)) { - err = PTR_ERR(n->thread); + if (IS_ERR(thread)) { + int err = PTR_ERR(thread); + pr_err("kthread_run failed with err %d\n", err); - n->thread = NULL; + return err; } - - return err; + WRITE_ONCE(n->thread, thread); + WRITE_ONCE(n->thread_pid_nr, task_pid_nr(thread)); + return 0; } static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack) @@ -6668,6 +6670,7 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi, set_bit(NAPI_STATE_SCHED, &napi->state); set_bit(NAPI_STATE_NPSVC, &napi->state); list_add_rcu(&napi->dev_list, &dev->napi_list); + netif_napi_set_irq(napi, -1); napi_hash_add(napi); napi_get_frags_check(napi); /* Create kthread for this napi if dev->threaded is set. @@ -6676,7 +6679,6 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi, */ if (dev->threaded && napi_kthread_create(napi)) dev->threaded = false; - netif_napi_set_irq(napi, -1); } EXPORT_SYMBOL(netif_napi_add_weight); @@ -6753,7 +6755,8 @@ void __netif_napi_del(struct napi_struct *napi) if (napi->thread) { kthread_stop(napi->thread); - napi->thread = NULL; + WRITE_ONCE(napi->thread, NULL); + WRITE_ONCE(napi->thread_pid_nr, 0); } } EXPORT_SYMBOL(__netif_napi_del); diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c index 1cb954f2d39e8248bffd854cdf27eceb25293425..0dcfe3527c122884c5713e56d5e27d4e638d936f 100644 --- a/net/core/netdev-genl.c +++ b/net/core/netdev-genl.c @@ -163,10 +163,11 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi, { void *hdr; pid_t pid; + int irq; if (WARN_ON_ONCE(!napi->dev)) return -EINVAL; - if (!(napi->dev->flags & IFF_UP)) + if (!(READ_ONCE(napi->dev->flags) & IFF_UP)) return 0; hdr = genlmsg_iput(rsp, info); @@ -177,17 +178,17 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi, nla_put_u32(rsp, NETDEV_A_NAPI_ID, napi->napi_id)) goto nla_put_failure; - if (nla_put_u32(rsp, NETDEV_A_NAPI_IFINDEX, napi->dev->ifindex)) + if (nla_put_u32(rsp, NETDEV_A_NAPI_IFINDEX, + READ_ONCE(napi->dev->ifindex))) goto nla_put_failure; - if (napi->irq >= 0 && nla_put_u32(rsp, NETDEV_A_NAPI_IRQ, napi->irq)) + irq = READ_ONCE(napi->irq); + if (irq >= 0 && nla_put_u32(rsp, NETDEV_A_NAPI_IRQ, irq)) goto nla_put_failure; - if (napi->thread) { - pid = task_pid_nr(napi->thread); - if (nla_put_u32(rsp, NETDEV_A_NAPI_PID, pid)) - goto nla_put_failure; - } + pid = READ_ONCE(napi->thread_pid_nr); + if (pid && nla_put_u32(rsp, NETDEV_A_NAPI_PID, pid)) + goto nla_put_failure; genlmsg_end(rsp, hdr); @@ -214,7 +215,7 @@ int netdev_nl_napi_get_doit(struct sk_buff *skb, struct genl_info *info) if (!rsp) return -ENOMEM; - rtnl_lock(); + rcu_read_lock(); napi = napi_by_id(napi_id); if (napi) { @@ -224,7 +225,7 @@ int netdev_nl_napi_get_doit(struct sk_buff *skb, struct genl_info *info) err = -ENOENT; } - rtnl_unlock(); + rcu_read_unlock(); if (err) goto err_free_msg;