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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
|
