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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0198-net-move-xmit_recursion-to-per-task-variable-on-RT.patch | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/debian/patches-rt/0198-net-move-xmit_recursion-to-per-task-variable-on-RT.patch b/debian/patches-rt/0198-net-move-xmit_recursion-to-per-task-variable-on-RT.patch new file mode 100644 index 000000000..242d9fd91 --- /dev/null +++ b/debian/patches-rt/0198-net-move-xmit_recursion-to-per-task-variable-on-RT.patch @@ -0,0 +1,189 @@ +From 5b1c12f86da1a979d45cda068adc9b597bc37e53 Mon Sep 17 00:00:00 2001 +From: Clark Williams <williams@redhat.com> +Date: Fri, 17 Dec 2021 14:31:31 -0600 +Subject: [PATCH 198/347] net: move xmit_recursion to per-task variable on -RT +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +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 lock owner and counter to be per task instead per-CPU so +it counts the recursion properly on -RT. The owner is also a task now and not a +CPU number. + +Cc: stable-rt@vger.kernel.org +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Signed-off-by: Clark Williams <williams@redhat.com> +--- + include/linux/netdevice.h | 71 +++++++++++++++++++++++++++++++++++++-- + include/linux/sched.h | 3 ++ + net/core/dev.c | 6 +++- + 3 files changed, 77 insertions(+), 3 deletions(-) + +diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h +index d893dc112afc..dfec34087039 100644 +--- a/include/linux/netdevice.h ++++ b/include/linux/netdevice.h +@@ -588,7 +588,11 @@ struct netdev_queue { + * write-mostly part + */ + spinlock_t _xmit_lock ____cacheline_aligned_in_smp; ++#ifdef CONFIG_PREEMPT_RT_FULL ++ struct task_struct *xmit_lock_owner; ++#else + int xmit_lock_owner; ++#endif + /* + * Time (in jiffies) of last Tx + */ +@@ -3009,14 +3013,38 @@ static inline void input_queue_tail_incr_save(struct softnet_data *sd, + #endif + } + ++#define XMIT_RECURSION_LIMIT 8 + DECLARE_PER_CPU_ALIGNED(struct softnet_data, softnet_data); + ++#ifdef CONFIG_PREEMPT_RT_FULL ++static inline int dev_recursion_level(void) ++{ ++ return current->xmit_recursion; ++} ++ ++static inline bool dev_xmit_recursion(void) ++{ ++ return unlikely(current->xmit_recursion > ++ XMIT_RECURSION_LIMIT); ++} ++ ++static inline void dev_xmit_recursion_inc(void) ++{ ++ current->xmit_recursion++; ++} ++ ++static inline void dev_xmit_recursion_dec(void) ++{ ++ current->xmit_recursion--; ++} ++ ++#else ++ + static inline int dev_recursion_level(void) + { + return this_cpu_read(softnet_data.xmit.recursion); + } + +-#define XMIT_RECURSION_LIMIT 8 + static inline bool dev_xmit_recursion(void) + { + return unlikely(__this_cpu_read(softnet_data.xmit.recursion) > +@@ -3032,6 +3060,7 @@ static inline void dev_xmit_recursion_dec(void) + { + __this_cpu_dec(softnet_data.xmit.recursion); + } ++#endif + + void __netif_schedule(struct Qdisc *q); + void netif_schedule_queue(struct netdev_queue *txq); +@@ -3841,6 +3870,44 @@ static inline u32 netif_msg_init(int debug_value, int default_msg_enable_bits) + return (1U << debug_value) - 1; + } + ++#ifdef CONFIG_PREEMPT_RT_FULL ++static inline void netdev_queue_set_owner(struct netdev_queue *txq, int cpu) ++{ ++ txq->xmit_lock_owner = current; ++} ++ ++static inline void netdev_queue_clear_owner(struct netdev_queue *txq) ++{ ++ txq->xmit_lock_owner = NULL; ++} ++ ++static inline bool netdev_queue_has_owner(struct netdev_queue *txq) ++{ ++ if (txq->xmit_lock_owner != NULL) ++ return true; ++ return false; ++} ++ ++#else ++ ++static inline void netdev_queue_set_owner(struct netdev_queue *txq, int cpu) ++{ ++ txq->xmit_lock_owner = cpu; ++} ++ ++static inline void netdev_queue_clear_owner(struct netdev_queue *txq) ++{ ++ txq->xmit_lock_owner = -1; ++} ++ ++static inline bool netdev_queue_has_owner(struct netdev_queue *txq) ++{ ++ if (txq->xmit_lock_owner != -1) ++ return true; ++ return false; ++} ++#endif ++ + static inline void __netif_tx_lock(struct netdev_queue *txq, int cpu) + { + spin_lock(&txq->_xmit_lock); +@@ -3893,7 +3960,7 @@ static inline void __netif_tx_unlock_bh(struct netdev_queue *txq) + + static inline void txq_trans_update(struct netdev_queue *txq) + { +- if (txq->xmit_lock_owner != -1) ++ if (netdev_queue_has_owner(txq)) + txq->trans_start = jiffies; + } + +diff --git a/include/linux/sched.h b/include/linux/sched.h +index ceb3bdfb6bc4..b7a357635d60 100644 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -1218,6 +1218,9 @@ struct task_struct { + #endif + #ifdef CONFIG_DEBUG_ATOMIC_SLEEP + unsigned long task_state_change; ++#endif ++#ifdef CONFIG_PREEMPT_RT_FULL ++ int xmit_recursion; + #endif + int pagefault_disabled; + #ifdef CONFIG_MMU +diff --git a/net/core/dev.c b/net/core/dev.c +index c279375fa5b9..a59b1db02f8b 100644 +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -3833,10 +3833,14 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev) + if (dev->flags & IFF_UP) { + int cpu = smp_processor_id(); /* ok because BHs are off */ + ++#ifdef CONFIG_PREEMPT_RT_FULL ++ if (READ_ONCE(txq->xmit_lock_owner) != current) { ++#else + /* Other cpus might concurrently change txq->xmit_lock_owner + * to -1 or to their cpu id, but not to our id. + */ + if (READ_ONCE(txq->xmit_lock_owner) != cpu) { ++#endif + if (dev_xmit_recursion()) + goto recursion_alert; + +@@ -8594,7 +8598,7 @@ static void netdev_init_one_queue(struct net_device *dev, + /* Initialize queue lock */ + spin_lock_init(&queue->_xmit_lock); + netdev_set_xmit_lockdep_class(&queue->_xmit_lock, dev->type); +- queue->xmit_lock_owner = -1; ++ netdev_queue_clear_owner(queue); + netdev_queue_numa_node_write(queue, NUMA_NO_NODE); + queue->dev = dev; + #ifdef CONFIG_BQL +-- +2.36.1 + |