[PATCH RT 03/20] net: move xmit_recursion to per-task variable on -RT
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2016-03-02 15:42:27
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Subsystem:
networking drivers, networking [general], scheduler, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot, Linus Torvalds
3.18.27-rt27-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> 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> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- include/linux/netdevice.h | 9 +++++++++ include/linux/sched.h | 1 + net/core/dev.c | 41 ++++++++++++++++++++++++++++++++++++++--- 3 files changed, 48 insertions(+), 3 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ff0f50dcea4a..dab2603bcdba 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h@@ -2130,11 +2130,20 @@ 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 bdc27dbffbe2..d05f52dcc0f4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h@@ -1523,6 +1523,7 @@ struct task_struct { struct mutex_waiter *blocked_on; #endif #ifdef CONFIG_PREEMPT_RT_FULL + int xmit_recursion; int pagefault_disabled; #endif #ifdef CONFIG_TRACE_IRQFLAGS
diff --git a/net/core/dev.c b/net/core/dev.c
index 39d2a0ba38ed..b89a1dd9f4d8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -2861,9 +2861,44 @@ 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 /**
@@ -2965,7 +3000,7 @@ 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);
@@ -2975,9 +3010,9 @@ 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