3.18.27-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
include/linux/netdevice.h | 9 +++++++++
include/linux/sched.h | 1 +
net/core/dev.c | 41 ++++++++++++++++++++++++++++++++++++++---
3 files changed, 48 insertions(+), 3 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ff0f50dcea4a..dab2603bcdba 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2130,11 +2130,20 @@ void netdev_freemem(struct net_device *dev);
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);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index bdc27dbffbe2..d05f52dcc0f4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1523,6 +1523,7 @@ struct task_struct {
struct mutex_waiter *blocked_on;
#endif
#ifdef CONFIG_PREEMPT_RT_FULL
+ int xmit_recursion;
int pagefault_disabled;
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
diff --git a/net/core/dev.c b/net/core/dev.c
index 39d2a0ba38ed..b89a1dd9f4d8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2861,9 +2861,44 @@ static void skb_update_prio(struct sk_buff *skb)
#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
/**
@@ -2965,7 +3000,7 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
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);
@@ -2975,9 +3010,9 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
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;
--
2.7.0
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