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Subject[PATCH net] u64_stats: fix u64_stats_init() for lockdep when used repeatedly in one file
Date
Fix bogus lockdep warnings if multiple u64_stats_sync variables are
initialized in the same file.

With CONFIG_LOCKDEP, seqcount_init() is a macro which declares:

static struct lock_class_key __key;

Since u64_stats_init() is a function (albeit an inline one), all calls
within the same file end up using the same instance, effectively treating
them all as a single lock-class.

Fixes: 9464ca650008 ("net: make u64_stats_init() a function")
Closes: https://lore.kernel.org/netdev/ea1567d9-ce66-45e6-8168-ac40a47d1821@roeck-us.net/
Signed-off-by: Petr Tesarik <petr@tesarici.cz>
---
include/linux/u64_stats_sync.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index ffe48e69b3f3..457879938fc1 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -135,10 +135,11 @@ static inline void u64_stats_inc(u64_stats_t *p)
p->v++;
}

-static inline void u64_stats_init(struct u64_stats_sync *syncp)
-{
- seqcount_init(&syncp->seq);
-}
+#define u64_stats_init(syncp) \
+ do { \
+ struct u64_stats_sync *__s = (syncp); \
+ seqcount_init(&__s->seq); \
+ } while (0)

static inline void __u64_stats_update_begin(struct u64_stats_sync *syncp)
{
--
2.44.0

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