diff options
Diffstat (limited to 'patches/net-move-xmit_recursion-to-per-task-variable-on-RT.patch')
| -rw-r--r-- | patches/net-move-xmit_recursion-to-per-task-variable-on-RT.patch | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/patches/net-move-xmit_recursion-to-per-task-variable-on-RT.patch b/patches/net-move-xmit_recursion-to-per-task-variable-on-RT.patch new file mode 100644 index 000000000000..cfce7cb0de64 --- /dev/null +++ b/patches/net-move-xmit_recursion-to-per-task-variable-on-RT.patch @@ -0,0 +1,125 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Wed, 13 Jan 2016 15:55:02 +0100 +Subject: 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> +--- + include/linux/netdevice.h | 9 +++++++++ + include/linux/sched.h | 3 +++ + net/core/dev.c | 41 ++++++++++++++++++++++++++++++++++++++--- + 3 files changed, 50 insertions(+), 3 deletions(-) + +--- a/include/linux/netdevice.h ++++ b/include/linux/netdevice.h +@@ -2249,11 +2249,20 @@ void netdev_freemem(struct net_device *d + 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); +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -1851,6 +1851,9 @@ 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; +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -2940,9 +2940,44 @@ static void skb_update_prio(struct sk_bu + #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 + + /** +@@ -3135,7 +3170,7 @@ static int __dev_queue_xmit(struct sk_bu + + 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); +@@ -3145,9 +3180,9 @@ static int __dev_queue_xmit(struct sk_bu + 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; |