From 80cd613a9ae091dbf52e27a409d58da988ffc8f3 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 25 Mar 2024 18:39:08 +0100 Subject: [PATCH] rcu: Mollify sparse with RCU guard When using "guard(rcu)();" sparse will complain, because even though it now understands the cleanup attribute, it doesn't evaluate the calls from it at function exit, and thus doesn't count the context correctly. Given that there's a conditional in the resulting code: static inline void class_rcu_destructor(class_rcu_t *_T) { if (_T->lock) { rcu_read_unlock(); } } it seems that even trying to teach sparse to evalulate the cleanup attribute function it'd still be difficult to really make it understand the full context here. Suppress the sparse warning by just releasing the context in the acquisition part of the function, after all we know it's safe with the guard, that's the whole point of it. Signed-off-by: Johannes Berg Reviewed-by: Boqun Feng Signed-off-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- include/linux/rcupdate.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 382780bb60f4e..dfd2399f2cde0 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1090,6 +1090,18 @@ rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) extern int rcu_expedited; extern int rcu_normal; -DEFINE_LOCK_GUARD_0(rcu, rcu_read_lock(), rcu_read_unlock()) +DEFINE_LOCK_GUARD_0(rcu, + do { + rcu_read_lock(); + /* + * sparse doesn't call the cleanup function, + * so just release immediately and don't track + * the context. We don't need to anyway, since + * the whole point of the guard is to not need + * the explicit unlock. + */ + __release(RCU); + } while (0), + rcu_read_unlock()) #endif /* __LINUX_RCUPDATE_H */