From c3ac7cf1847a4e68c909984f60d36adef2088e35 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 10 Sep 2015 16:29:02 -0700 Subject: [PATCH] rcu: Add rcu_pointer_handoff() This commit adds an rcu_pointer_handoff() that is intended to mark situations where a structure's protection transitions from RCU to some other mechanism (locking, reference counting, whatever). These markings should allow external tools to more easily spot bugs involving leaking pointers out of RCU read-side critical sections. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 6c3ceceb6148..587eb057e2fa 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -812,6 +812,28 @@ static inline void rcu_preempt_sleep_check(void) */ #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) +/** + * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism + * @p: The pointer to hand off + * + * This is simply an identity function, but it documents where a pointer + * is handed off from RCU to some other synchronization mechanism, for + * example, reference counting or locking. In C11, it would map to + * kill_dependency(). It could be used as follows: + * + * rcu_read_lock(); + * p = rcu_dereference(gp); + * long_lived = is_long_lived(p); + * if (long_lived) { + * if (!atomic_inc_not_zero(p->refcnt)) + * long_lived = false; + * else + * p = rcu_pointer_handoff(p); + * } + * rcu_read_unlock(); + */ +#define rcu_pointer_handoff(p) (p) + /** * rcu_read_lock() - mark the beginning of an RCU read-side critical section * -- 2.39.5