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 <k...@kernel.org>
Signed-off-by: Yunsheng Lin <linyunsh...@huawei.com>
---
V3: add comment to emphasize the ambiguous semantics.
---
include/linux/lockdep.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index f559487..8d60f46 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -594,6 +594,13 @@ do {
\
this_cpu_read(hardirqs_enabled))); \
} while (0)
+/* 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 +612,7 @@ 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
--
2.8.1
