On Thu, 29 Oct 2020 19:34:48 +0800 Yunsheng Lin wrote:
> 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 a in_softirq() debug checking in napi_consume_skb() to catch
> this kind of error.
>
> Suggested-by: Eric Dumazet <eduma...@google.com>
> Signed-off-by: Yunsheng Lin <linyunsh...@huawei.com>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 1ba8f01..1834007 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -897,6 +897,10 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
> return;
> }
>
> + DEBUG_NET_WARN(!in_softirq(),
> + "%s is called with non-zero budget outside softirq
> context.\n",
> + __func__);
Can't we use lockdep instead of defining our own knobs?
Like this maybe?
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index f5594879175a..5253a167d00c 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -594,6 +594,14 @@ do {
\
this_cpu_read(hardirqs_enabled))); \
} while (0)
+#define lockdep_assert_in_softirq() \
+do { \
+ WARN_ON_ONCE(__lockdep_enabled && \
+ (softirq_count() == 0 || \
+ this_cpu_read(hardirq_context))); \
+} while (0)
> if (!skb_unref(skb))
> return;
>
