[PATCH RFC] net: add in_softirq() debug checking in napi_consume_skb()
From: Yunsheng Lin <hidden>
Date: 2020-09-22 11:40:17
Also in:
lkml
Subsystem:
networking drivers, networking [general], the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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> --- include/linux/netdevice.h | 6 ++++++ net/Kconfig | 7 +++++++ net/core/skbuff.c | 4 ++++ 3 files changed, 17 insertions(+)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fef0eb9..e06d5e5 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h@@ -5095,6 +5095,12 @@ do { \ }) #endif +#if defined(CONFIG_DEBUG_NET) +#define DEBUG_NET_WARN(condition, ...) WARN(condition, ##__VA_ARGS__) +#else +#define DEBUG_NET_WARN(condition, ...) +#endif + /* * The list of packet types we will receive (as opposed to discard) * and the routines to invoke.
diff --git a/net/Kconfig b/net/Kconfig
index 3831206..b176670 100644
--- a/net/Kconfig
+++ b/net/Kconfig@@ -460,6 +460,13 @@ config ETHTOOL_NETLINK netlink. It provides better extensibility and some new features, e.g. notification messages. +config DEBUG_NET + bool "Net debugging and diagnostics" + depends on DEBUG_KERNEL + default n + help + Say Y here to add some extra checks and diagnostics to networking. + endif # if NET # Used by archs to tell that they support BPF JIT compiler plus which flavour.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e077447..378e66c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c@@ -901,6 +901,10 @@ 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__); + if (!skb_unref(skb)) return;
--
2.8.1