268 lines
6.8 KiB
Diff
268 lines
6.8 KiB
Diff
From 4614b75f982f6d986f99de8d4d35afd3da7140b4 Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 13 Jan 2016 15:55:02 +0100
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Subject: [PATCH 199/291] net: move xmit_recursion to per-task variable on -RT
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.90-rt35.tar.xz
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A softirq on -RT can be preempted. That means one task is in
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__dev_queue_xmit(), gets preempted and another task may enter
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__dev_queue_xmit() aw well. netperf together with a bridge device
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will then trigger the `recursion alert` because each task increments
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the xmit_recursion variable which is per-CPU.
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A virtual device like br0 is required to trigger this warning.
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This patch moves the lock owner and counter to be per task instead per-CPU so
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it counts the recursion properly on -RT. The owner is also a task now and not a
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CPU number.
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Cc: stable-rt@vger.kernel.org
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/netdevice.h | 95 ++++++++++++++++++++++++++++++++++++---
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include/linux/sched.h | 3 ++
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net/core/dev.c | 15 ++++---
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net/core/filter.c | 6 +--
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4 files changed, 104 insertions(+), 15 deletions(-)
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--- a/include/linux/netdevice.h
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+++ b/include/linux/netdevice.h
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@@ -587,7 +587,11 @@
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* write-mostly part
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*/
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spinlock_t _xmit_lock ____cacheline_aligned_in_smp;
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ struct task_struct *xmit_lock_owner;
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+#else
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int xmit_lock_owner;
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+#endif
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/*
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* Time (in jiffies) of last Tx
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*/
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@@ -2620,14 +2624,53 @@
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void synchronize_net(void);
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int init_dummy_netdev(struct net_device *dev);
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-DECLARE_PER_CPU(int, xmit_recursion);
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#define XMIT_RECURSION_LIMIT 10
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+static inline int dev_recursion_level(void)
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+{
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+ return current->xmit_recursion;
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+}
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+
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+static inline int xmit_rec_read(void)
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+{
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+ return current->xmit_recursion;
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+}
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+
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+static inline void xmit_rec_inc(void)
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+{
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+ current->xmit_recursion++;
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+}
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+
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+static inline void xmit_rec_dec(void)
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+{
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+ current->xmit_recursion--;
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+}
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+
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+#else
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+
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+DECLARE_PER_CPU(int, xmit_recursion);
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static inline int dev_recursion_level(void)
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{
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return this_cpu_read(xmit_recursion);
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}
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+static inline int xmit_rec_read(void)
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+{
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+ return __this_cpu_read(xmit_recursion);
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+}
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+
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+static inline void xmit_rec_inc(void)
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+{
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+ __this_cpu_inc(xmit_recursion);
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+}
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+
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+static inline void xmit_rec_dec(void)
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+{
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+ __this_cpu_dec(xmit_recursion);
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+}
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+#endif
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+
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struct net_device *dev_get_by_index(struct net *net, int ifindex);
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struct net_device *__dev_get_by_index(struct net *net, int ifindex);
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struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
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@@ -3803,10 +3846,48 @@
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return (1U << debug_value) - 1;
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}
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+static inline void netdev_queue_set_owner(struct netdev_queue *txq, int cpu)
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+{
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+ txq->xmit_lock_owner = current;
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+}
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+
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+static inline void netdev_queue_clear_owner(struct netdev_queue *txq)
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+{
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+ txq->xmit_lock_owner = NULL;
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+}
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+
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+static inline bool netdev_queue_has_owner(struct netdev_queue *txq)
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+{
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+ if (txq->xmit_lock_owner != NULL)
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+ return true;
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+ return false;
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+}
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+
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+#else
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+
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+static inline void netdev_queue_set_owner(struct netdev_queue *txq, int cpu)
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+{
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+ txq->xmit_lock_owner = cpu;
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+}
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+
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+static inline void netdev_queue_clear_owner(struct netdev_queue *txq)
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+{
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+ txq->xmit_lock_owner = -1;
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+}
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+
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+static inline bool netdev_queue_has_owner(struct netdev_queue *txq)
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+{
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+ if (txq->xmit_lock_owner != -1)
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+ return true;
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+ return false;
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+}
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+#endif
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+
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static inline void __netif_tx_lock(struct netdev_queue *txq, int cpu)
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{
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spin_lock(&txq->_xmit_lock);
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- txq->xmit_lock_owner = cpu;
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+ netdev_queue_set_owner(txq, cpu);
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}
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static inline bool __netif_tx_acquire(struct netdev_queue *txq)
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@@ -3823,32 +3904,32 @@
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static inline void __netif_tx_lock_bh(struct netdev_queue *txq)
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{
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spin_lock_bh(&txq->_xmit_lock);
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- txq->xmit_lock_owner = smp_processor_id();
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+ netdev_queue_set_owner(txq, smp_processor_id());
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}
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static inline bool __netif_tx_trylock(struct netdev_queue *txq)
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{
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bool ok = spin_trylock(&txq->_xmit_lock);
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if (likely(ok))
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- txq->xmit_lock_owner = smp_processor_id();
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+ netdev_queue_set_owner(txq, smp_processor_id());
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return ok;
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}
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static inline void __netif_tx_unlock(struct netdev_queue *txq)
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{
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- txq->xmit_lock_owner = -1;
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+ netdev_queue_clear_owner(txq);
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spin_unlock(&txq->_xmit_lock);
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}
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static inline void __netif_tx_unlock_bh(struct netdev_queue *txq)
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{
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- txq->xmit_lock_owner = -1;
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+ netdev_queue_clear_owner(txq);
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spin_unlock_bh(&txq->_xmit_lock);
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}
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static inline void txq_trans_update(struct netdev_queue *txq)
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{
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- if (txq->xmit_lock_owner != -1)
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+ if (netdev_queue_has_owner(txq))
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txq->trans_start = jiffies;
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}
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -1217,6 +1217,9 @@
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#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
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unsigned long task_state_change;
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#endif
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ int xmit_recursion;
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+#endif
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int pagefault_disabled;
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#ifdef CONFIG_MMU
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struct task_struct *oom_reaper_list;
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -3538,8 +3538,10 @@
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#define skb_update_prio(skb)
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#endif
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+#ifndef CONFIG_PREEMPT_RT_FULL
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DEFINE_PER_CPU(int, xmit_recursion);
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EXPORT_SYMBOL(xmit_recursion);
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+#endif
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/**
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* dev_loopback_xmit - loop back @skb
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@@ -3830,9 +3832,12 @@
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if (dev->flags & IFF_UP) {
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int cpu = smp_processor_id(); /* ok because BHs are off */
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ if (txq->xmit_lock_owner != current) {
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+#else
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if (txq->xmit_lock_owner != cpu) {
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- if (unlikely(__this_cpu_read(xmit_recursion) >
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- XMIT_RECURSION_LIMIT))
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+#endif
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+ if (unlikely(xmit_rec_read() > XMIT_RECURSION_LIMIT))
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goto recursion_alert;
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skb = validate_xmit_skb(skb, dev, &again);
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@@ -3842,9 +3847,9 @@
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HARD_TX_LOCK(dev, txq, cpu);
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if (!netif_xmit_stopped(txq)) {
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- __this_cpu_inc(xmit_recursion);
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+ xmit_rec_inc();
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skb = dev_hard_start_xmit(skb, dev, txq, &rc);
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- __this_cpu_dec(xmit_recursion);
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+ xmit_rec_dec();
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if (dev_xmit_complete(rc)) {
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HARD_TX_UNLOCK(dev, txq);
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goto out;
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@@ -8583,7 +8588,7 @@
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/* Initialize queue lock */
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spin_lock_init(&queue->_xmit_lock);
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netdev_set_xmit_lockdep_class(&queue->_xmit_lock, dev->type);
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- queue->xmit_lock_owner = -1;
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+ netdev_queue_clear_owner(queue);
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netdev_queue_numa_node_write(queue, NUMA_NO_NODE);
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queue->dev = dev;
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#ifdef CONFIG_BQL
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--- a/net/core/filter.c
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+++ b/net/core/filter.c
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@@ -2000,7 +2000,7 @@
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{
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int ret;
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- if (unlikely(__this_cpu_read(xmit_recursion) > XMIT_RECURSION_LIMIT)) {
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+ if (unlikely(xmit_rec_read() > XMIT_RECURSION_LIMIT)) {
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net_crit_ratelimited("bpf: recursion limit reached on datapath, buggy bpf program?\n");
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kfree_skb(skb);
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return -ENETDOWN;
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@@ -2009,9 +2009,9 @@
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skb->dev = dev;
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skb->tstamp = 0;
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- __this_cpu_inc(xmit_recursion);
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+ xmit_rec_inc();
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ret = dev_queue_xmit(skb);
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- __this_cpu_dec(xmit_recursion);
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+ xmit_rec_dec();
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return ret;
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}
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