Re: [PATCH net-next] net: add in_softirq() debug checking in napi_consume_skb()
From: Jakub Kicinski <kuba@kernel.org>
Date: 2020-10-31 22:44:42
Also in:
lkml
Subsystem:
locking primitives, the rest · Maintainers:
Peter Zijlstra, Ingo Molnar, Will Deacon, Boqun Feng, Linus Torvalds
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 <edumazet@google.com> Signed-off-by: Yunsheng Lin <redacted>
quoted hunk ↗ jump to hunk
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;