4.1.15-rt18-rc1 stable review patch. If anyone has any objections, please let me know.
------------------ From: Sebastian Andrzej Siewior <[email protected]> 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: [email protected] Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Steven Rostedt <[email protected]> --- include/linux/netdevice.h | 9 +++++++++ include/linux/sched.h | 3 +++ net/core/dev.c | 41 ++++++++++++++++++++++++++++++++++++++--- 3 files changed, 50 insertions(+), 3 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 7a289e802a23..d24fe5d9980d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2192,11 +2192,20 @@ void netdev_freemem(struct net_device *dev); void synchronize_net(void); int init_dummy_netdev(struct net_device *dev); +#ifdef CONFIG_PREEMPT_RT_FULL +static inline int dev_recursion_level(void) +{ + return current->xmit_recursion; +} + +#else + DECLARE_PER_CPU(int, xmit_recursion); static inline int dev_recursion_level(void) { return this_cpu_read(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); diff --git a/include/linux/sched.h b/include/linux/sched.h index 1a56c0512491..4d995add9497 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1806,6 +1806,9 @@ 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; }; diff --git a/net/core/dev.c b/net/core/dev.c index 16fbef81024d..7d8ad99de55f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2883,9 +2883,44 @@ static void skb_update_prio(struct sk_buff *skb) #define skb_update_prio(skb) #endif +#ifdef CONFIG_PREEMPT_RT_FULL + +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 + DEFINE_PER_CPU(int, xmit_recursion); EXPORT_SYMBOL(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 int xmit_rec_dec(void) +{ + __this_cpu_dec(xmit_recursion); +} +#endif + #define RECURSION_LIMIT 10 /** @@ -2987,7 +3022,7 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv) if (txq->xmit_lock_owner != cpu) { - if (__this_cpu_read(xmit_recursion) > RECURSION_LIMIT) + if (xmit_rec_read() > RECURSION_LIMIT) goto recursion_alert; skb = validate_xmit_skb(skb, dev); @@ -2997,9 +3032,9 @@ 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; -- 2.7.0
