Merge branch 'add-an-assert-in-napi_consume_skb'

Yunsheng Lin says:

====================
Add an assert in napi_consume_skb()

This patch introduces a lockdep_assert_in_softirq() interface and
uses it to assert the case when napi_consume_skb() is not called in
the softirq context.
====================

Link: https://lore.kernel.org/r/1606214969-97849-1-git-send-email-linyunsheng@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/lockdep.h

@@ -594,6 +594,16 @@ do {									\
 		      this_cpu_read(hardirqs_enabled)));		\
 } while (0)
 
+/*
+ * Acceptable for protecting per-CPU resources accessed from BH.
+ * Much like in_softirq() - semantics are ambiguous, use carefully.
+ */
+#define lockdep_assert_in_softirq()					\
+do {									\
+	WARN_ON_ONCE(__lockdep_enabled			&&		\
+		     (!in_softirq() || in_irq() || in_nmi()));		\
+} while (0)
+
 #else
 # define might_lock(lock) do { } while (0)
 # define might_lock_read(lock) do { } while (0)
@@ -605,6 +615,7 @@ do {									\
 
 # define lockdep_assert_preemption_enabled() do { } while (0)
 # define lockdep_assert_preemption_disabled() do { } while (0)
+# define lockdep_assert_in_softirq() do { } while (0)
 #endif
 
 #ifdef CONFIG_PROVE_RAW_LOCK_NESTING

net/core/skbuff.c

@@ -902,6 +902,8 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
 		return;
 	}
 
+	lockdep_assert_in_softirq();
+
 	if (!skb_unref(skb))
 		return;