127 lines
3.4 KiB
Diff
127 lines
3.4 KiB
Diff
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
|
|
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4-rt3.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 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;
|