From 8e74e4845d1825e91b3209872dad7895aaa219f1 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 13 Jan 2016 15:55:02 +0100 Subject: [PATCH 236/352] net: move xmit_recursion to per-task variable on -RT A softirq on -RT can be preempted. That means one task is in __dev_queue_xmit(), gets preempted and another task may enter __dev_queue_xmit() aw well. netperf together with a bridge device will then trigger the `recursion alert` because each task increments the xmit_recursion variable which is per-CPU. A virtual device like br0 is required to trigger this warning. This patch moves the counter to per task instead per-CPU so it counts the recursion properly on -RT. Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior --- include/linux/netdevice.h | 41 ++++++++++++++++++++++++++++++++++++++++- include/linux/sched.h | 3 +++ net/core/dev.c | 9 +++++---- net/core/filter.c | 6 +++--- 4 files changed, 51 insertions(+), 8 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index b495762..54ca094 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2471,14 +2471,53 @@ void netdev_freemem(struct net_device *dev); void synchronize_net(void); int init_dummy_netdev(struct net_device *dev); -DECLARE_PER_CPU(int, xmit_recursion); #define XMIT_RECURSION_LIMIT 10 +#ifdef CONFIG_PREEMPT_RT_FULL +static inline int dev_recursion_level(void) +{ + return current->xmit_recursion; +} + +static inline int xmit_rec_read(void) +{ + return current->xmit_recursion; +} + +static inline void xmit_rec_inc(void) +{ + current->xmit_recursion++; +} + +static inline void xmit_rec_dec(void) +{ + current->xmit_recursion--; +} + +#else + +DECLARE_PER_CPU(int, xmit_recursion); static inline int dev_recursion_level(void) { return this_cpu_read(xmit_recursion); } +static inline int xmit_rec_read(void) +{ + return __this_cpu_read(xmit_recursion); +} + +static inline void xmit_rec_inc(void) +{ + __this_cpu_inc(xmit_recursion); +} + +static inline void xmit_rec_dec(void) +{ + __this_cpu_dec(xmit_recursion); +} +#endif + struct net_device *dev_get_by_index(struct net *net, int ifindex); struct net_device *__dev_get_by_index(struct net *net, int ifindex); struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex); diff --git a/include/linux/sched.h b/include/linux/sched.h index 3950b85..93ae84c 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2175,6 +2175,9 @@ struct task_struct { #ifdef CONFIG_DEBUG_ATOMIC_SLEEP unsigned long task_state_change; #endif +#ifdef CONFIG_PREEMPT_RT_FULL + int xmit_recursion; +#endif int pagefault_disabled; #ifdef CONFIG_MMU struct task_struct *oom_reaper_list; diff --git a/net/core/dev.c b/net/core/dev.c index 7e9749e..1b44303 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3225,8 +3225,10 @@ static void skb_update_prio(struct sk_buff *skb) #define skb_update_prio(skb) #endif +#ifndef CONFIG_PREEMPT_RT_FULL DEFINE_PER_CPU(int, xmit_recursion); EXPORT_SYMBOL(xmit_recursion); +#endif /** * dev_loopback_xmit - loop back @skb @@ -3460,8 +3462,7 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv) int cpu = smp_processor_id(); /* ok because BHs are off */ if (txq->xmit_lock_owner != cpu) { - if (unlikely(__this_cpu_read(xmit_recursion) > - XMIT_RECURSION_LIMIT)) + if (unlikely(xmit_rec_read() > XMIT_RECURSION_LIMIT)) goto recursion_alert; skb = validate_xmit_skb(skb, dev); @@ -3471,9 +3472,9 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv) HARD_TX_LOCK(dev, txq, cpu); if (!netif_xmit_stopped(txq)) { - __this_cpu_inc(xmit_recursion); + xmit_rec_inc(); skb = dev_hard_start_xmit(skb, dev, txq, &rc); - __this_cpu_dec(xmit_recursion); + xmit_rec_dec(); if (dev_xmit_complete(rc)) { HARD_TX_UNLOCK(dev, txq); goto out; diff --git a/net/core/filter.c b/net/core/filter.c index c385c55..feb96c2 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1657,7 +1657,7 @@ static inline int __bpf_tx_skb(struct net_device *dev, struct sk_buff *skb) { int ret; - if (unlikely(__this_cpu_read(xmit_recursion) > XMIT_RECURSION_LIMIT)) { + if (unlikely(xmit_rec_read() > XMIT_RECURSION_LIMIT)) { net_crit_ratelimited("bpf: recursion limit reached on datapath, buggy bpf program?\n"); kfree_skb(skb); return -ENETDOWN; @@ -1665,9 +1665,9 @@ static inline int __bpf_tx_skb(struct net_device *dev, struct sk_buff *skb) skb->dev = dev; - __this_cpu_inc(xmit_recursion); + xmit_rec_inc(); ret = dev_queue_xmit(skb); - __this_cpu_dec(xmit_recursion); + xmit_rec_dec(); return ret; } -- 2.7.4