netdev - [PATCH net-next v4 5/6] page_pool: add a lockdep check for recycling in hardirq

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Date: Fri,  4 Aug 2023 20:05:28 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
	Larysa Zaremba <larysa.zaremba@...el.com>,
	Yunsheng Lin <linyunsheng@...wei.com>,
	Alexander Duyck <alexanderduyck@...com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Simon Horman <simon.horman@...igine.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net-next v4 5/6] page_pool: add a lockdep check for recycling in hardirq

From: Jakub Kicinski <kuba@...nel.org>

Page pool use in hardirq is prohibited, add debug checks
to catch misuses. IIRC we previously discussed using
DEBUG_NET_WARN_ON_ONCE() for this, but there were concerns
that people will have DEBUG_NET enabled in perf testing.
I don't think anyone enables lockdep in perf testing,
so use lockdep to avoid pushback and arguing :)

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
 include/linux/lockdep.h | 7 +++++++
 net/core/page_pool.c    | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 310f85903c91..dc2844b071c2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -625,6 +625,12 @@ do {									\
 	WARN_ON_ONCE(__lockdep_enabled && !this_cpu_read(hardirq_context)); \
 } while (0)
 
+#define lockdep_assert_no_hardirq()					\
+do {									\
+	WARN_ON_ONCE(__lockdep_enabled && (this_cpu_read(hardirq_context) || \
+					   !this_cpu_read(hardirqs_enabled))); \
+} while (0)
+
 #define lockdep_assert_preemption_enabled()				\
 do {									\
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)	&&		\
@@ -659,6 +665,7 @@ do {									\
 # define lockdep_assert_irqs_enabled() do { } while (0)
 # define lockdep_assert_irqs_disabled() do { } while (0)
 # define lockdep_assert_in_irq() do { } while (0)
+# define lockdep_assert_no_hardirq() do { } while (0)
 
 # define lockdep_assert_preemption_enabled() do { } while (0)
 # define lockdep_assert_preemption_disabled() do { } while (0)
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 03ad74d25959..77cb75e63aca 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -587,6 +587,8 @@ static __always_inline struct page *
 __page_pool_put_page(struct page_pool *pool, struct page *page,
 		     unsigned int dma_sync_size, bool allow_direct)
 {
+	lockdep_assert_no_hardirq();
+
 	/* This allocator is optimized for the XDP mode that uses
 	 * one-frame-per-page, but have fallbacks that act like the
 	 * regular page allocator APIs.
-- 
2.41.0