Commit 8b5536ad authored Nov 24, 2020 by Yunsheng Lin Committed by Jakub Kicinski Nov 25, 2020

lockdep: Introduce in_softirq lockdep assert



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 <kuba@kernel.org>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent b5094a3b

include/linux/lockdep.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -594,6 +594,16 @@ do { \
		this_cpu_read(hardirqs_enabled))); \
		} while (0)

		/*
		* Acceptable for protecting per-CPU resources accessed from BH.
		* 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 +615,7 @@ 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

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