lockdep: Introduce in_softirq lockdep assert

The current semantic for napi_consume_skb() is that caller need
to provide non-zero budget when calling from NAPI context, and
breaking this semantic will cause hard to debug problem, because
_kfree_skb_defer() need to run in atomic context in order to push
the skb to the particular cpu' napi_alloc_cache atomically.

So add the lockdep_assert_in_softirq() to assert when the running
context is not in_softirq, in_softirq means softirq is serving or
BH is disabled, which has a ambiguous semantics due to the BH
disabled confusion, so add a comment to emphasize that.

And the softirq context can be interrupted by hard IRQ or NMI
context, lockdep_assert_in_softirq() need to assert about hard
IRQ or NMI context too.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index f5594879175a6dc2833744565b15465d713f9322..92771bc1791f40177b074fa6309051a528673dde 100644 (file)
--- a/include/linux/lockdep.h
+++ b/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