net: move xmit_recursion to per-task variable on -RT

ported to 5.9. original commit
6a66ae877a187c6c34abfd0aae2bacf6dd1ccb00

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jan Sondhauss <jan.sondhauss@wago.com>

include/linux/netdevice.h

@@ -3284,24 +3284,41 @@ DECLARE_PER_CPU_ALIGNED(struct softnet_data, softnet_data);
 
 static inline int dev_recursion_level(void)
 {
+#ifdef CONFIG_PREEMPT_RT
+	return atomic_read(&current->xmit_recursion);
+#else
 	return this_cpu_read(softnet_data.xmit.recursion);
+#endif
 }
 
 #define XMIT_RECURSION_LIMIT	8
 static inline bool dev_xmit_recursion(void)
 {
+#ifdef CONFIG_PREEMPT_RT
+	return unlikely(atomic_read(&current->xmit_recursion) >
+			XMIT_RECURSION_LIMIT);
+#else
 	return unlikely(__this_cpu_read(softnet_data.xmit.recursion) >
 			XMIT_RECURSION_LIMIT);
+#endif
 }
 
 static inline void dev_xmit_recursion_inc(void)
 {
+#ifdef CONFIG_PREEMPT_RT
+	atomic_inc(&current->xmit_recursion);
+#else
 	__this_cpu_inc(softnet_data.xmit.recursion);
+#endif
 }
 
 static inline void dev_xmit_recursion_dec(void)
 {
+#ifdef CONFIG_PREEMPT_RT
+	atomic_dec(&current->xmit_recursion);
+#else
 	__this_cpu_dec(softnet_data.xmit.recursion);
+#endif
 }
 
 void __netif_schedule(struct Qdisc *q);

include/linux/sched.h

@@ -1539,6 +1539,10 @@ struct task_struct {
 	struct user_event_mm		*user_event_mm;
 #endif
 
+#ifdef CONFIG_PREEMPT_RT
+	atomic_t			xmit_recursion;
+#endif
+
 	/*
 	 * New fields for task_struct should be added above here, so that
 	 * they are included in the randomized portion of task_struct.

kernel/fork.c

@@ -1166,6 +1166,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	tsk->wake_q.next = NULL;
 	tsk->worker_private = NULL;
 
+#ifdef CONFIG_PREEMPT_RT
+	atomic_set(&tsk->xmit_recursion, 0);
+#endif
+
 	kcov_task_init(tsk);
 	kmsan_task_create(tsk);
 	kmap_local_fork(tsk);