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From 4045ef54237d468b1594d2ce78dd9643bc3a91f0 Mon Sep 17 00:00:00 2001
Message-Id: <4045ef54237d468b1594d2ce78dd9643bc3a91f0.1601675152.git.zanussi@kernel.org>
In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 13 Jan 2016 15:55:02 +0100
Subject: [PATCH 198/333] net: move xmit_recursion to per-task variable on -RT
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.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>
---
include/linux/netdevice.h | 81 +++++++++++++++++++++++++++++++++++----
include/linux/sched.h | 3 ++
net/core/dev.c | 6 ++-
3 files changed, 82 insertions(+), 8 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8fff010fff6e..7bf58533f955 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -587,7 +587,11 @@ 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
*/
@@ -2998,14 +3002,38 @@ 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) >
@@ -3021,6 +3049,7 @@ 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);
@@ -3824,10 +3853,48 @@ 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);
- txq->xmit_lock_owner = cpu;
+ netdev_queue_set_owner(txq, cpu);
}
static inline bool __netif_tx_acquire(struct netdev_queue *txq)
@@ -3844,32 +3911,32 @@ static inline void __netif_tx_release(struct netdev_queue *txq)
static inline void __netif_tx_lock_bh(struct netdev_queue *txq)
{
spin_lock_bh(&txq->_xmit_lock);
- txq->xmit_lock_owner = smp_processor_id();
+ netdev_queue_set_owner(txq, smp_processor_id());
}
static inline bool __netif_tx_trylock(struct netdev_queue *txq)
{
bool ok = spin_trylock(&txq->_xmit_lock);
if (likely(ok))
- txq->xmit_lock_owner = smp_processor_id();
+ netdev_queue_set_owner(txq, smp_processor_id());
return ok;
}
static inline void __netif_tx_unlock(struct netdev_queue *txq)
{
- txq->xmit_lock_owner = -1;
+ netdev_queue_clear_owner(txq);
spin_unlock(&txq->_xmit_lock);
}
static inline void __netif_tx_unlock_bh(struct netdev_queue *txq)
{
- txq->xmit_lock_owner = -1;
+ netdev_queue_clear_owner(txq);
spin_unlock_bh(&txq->_xmit_lock);
}
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 4a4f03a8d8d4..37334ec1ab3e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1216,6 +1216,9 @@ 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 fc1dfd57d4c0..03572f1205c6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3825,7 +3825,11 @@ 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 (txq->xmit_lock_owner != current) {
+#else
if (txq->xmit_lock_owner != cpu) {
+#endif
if (dev_xmit_recursion())
goto recursion_alert;
@@ -8570,7 +8574,7 @@ 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
--
2.17.1
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