net: Add lockdep asserts to ____napi_schedule().

____napi_schedule() needs to be invoked with disabled interrupts due to
__raise_softirq_irqoff (in order not to corrupt the per-CPU list).
____napi_schedule() needs also to be invoked from an interrupt context
so that the raised-softirq is processed while the interrupt context is
left.

Add lockdep asserts for both conditions.
While this is the second time the irq/softirq check is needed, provide a
generic lockdep_assert_softirq_will_run() which is used by both caller.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/lockdep.h

@@ -329,6 +329,12 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 
 #define lockdep_assert_none_held_once()		\
 	lockdep_assert_once(!current->lockdep_depth)
+/*
+ * Ensure that softirq is handled within the callchain and not delayed and
+ * handled by chance.
+ */
+#define lockdep_assert_softirq_will_run()	\
+	lockdep_assert_once(hardirq_count() | softirq_count())
 
 #define lockdep_recursing(tsk)	((tsk)->lockdep_recursion)
 
@@ -414,6 +420,7 @@ extern int lockdep_is_held(const void *);
 #define lockdep_assert_held_read(l)		do { (void)(l); } while (0)
 #define lockdep_assert_held_once(l)		do { (void)(l); } while (0)
 #define lockdep_assert_none_held_once()	do { } while (0)
+#define lockdep_assert_softirq_will_run()	do { } while (0)
 
 #define lockdep_recursing(tsk)			(0)
 

net/core/dev.c

@@ -4265,6 +4265,9 @@ static inline void ____napi_schedule(struct softnet_data *sd,
 {
 	struct task_struct *thread;
 
+	lockdep_assert_softirq_will_run();
+	lockdep_assert_irqs_disabled();
+
 	if (test_bit(NAPI_STATE_THREADED, &napi->state)) {
 		/* Paired with smp_mb__before_atomic() in
 		 * napi_enable()/dev_set_threaded().
@@ -4872,7 +4875,7 @@ int __netif_rx(struct sk_buff *skb)
 {
 	int ret;
 
-	lockdep_assert_once(hardirq_count() | softirq_count());
+	lockdep_assert_softirq_will_run();
 
 	trace_netif_rx_entry(skb);
 	ret = netif_rx_internal(skb);