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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-01-13 15:55:02 +0100 |
|---|---|---|
| committer | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-02-13 00:36:23 +0100 |
| commit | b2a4dd2ff01ea79757100a2c846c0a957213288c (patch) | |
| tree | 4d929bdc67d1e87c9445e39de4ac2928dc32be65 | |
| parent | 0c0a810b74b499a564accfe6c30ab8c767b18262 (diff) | |
| download | rt-linux-b2a4dd2ff01ea79757100a2c846c0a957213288c.tar.gz | |
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 <bigeasy@linutronix.de>
| -rw-r--r-- | include/linux/netdevice.h | 9 | ||||
| -rw-r--r-- | include/linux/sched.h | 3 | ||||
| -rw-r--r-- | 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 f14e39cb897c8..c0e12f7f0f132 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2249,11 +2249,20 @@ 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 d25e640036892..70b2ac2cb6b3e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1852,6 +1852,9 @@ 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; /* CPU-specific state of this task */ struct thread_struct thread; diff --git a/net/core/dev.c b/net/core/dev.c index c3246d24a3a5d..acb414aeeaa38 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2945,9 +2945,44 @@ 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 void xmit_rec_dec(void) +{ + __this_cpu_dec(xmit_recursion); +} +#endif + #define RECURSION_LIMIT 10 /** @@ -3140,7 +3175,7 @@ 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); @@ -3150,9 +3185,9 @@ 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; |