From 0909fc2b2c41aae50a18a36ac2858d156f521871 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 25 Feb 2021 17:36:06 -0800 Subject: rcu: Provide polling interfaces for Tiny RCU grace periods There is a need for a non-blocking polling interface for RCU grace periods, so this commit supplies start_poll_synchronize_rcu() and poll_state_synchronize_rcu() for this purpose. Note that the existing get_state_synchronize_rcu() may be used if future grace periods are inevitable (perhaps due to a later call_rcu() invocation). The new start_poll_synchronize_rcu() is to be used if future grace periods might not otherwise happen. Finally, poll_state_synchronize_rcu() provides a lockless check for a grace period having elapsed since the corresponding call to either of the get_state_synchronize_rcu() or start_poll_synchronize_rcu(). As with get_state_synchronize_rcu(), the return value from either get_state_synchronize_rcu() or start_poll_synchronize_rcu() is passed in to a later call to either poll_state_synchronize_rcu() or the existing (might_sleep) cond_synchronize_rcu(). [ paulmck: Revert cond_synchronize_rcu() to might_sleep() per Frederic Weisbecker feedback. ] Reviewed-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney --- include/linux/rcutiny.h | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'include/linux/rcutiny.h') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 2a97334eb786..35e0be326ffc 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -17,10 +17,9 @@ /* Never flag non-existent other CPUs! */ static inline bool rcu_eqs_special_set(int cpu) { return false; } -static inline unsigned long get_state_synchronize_rcu(void) -{ - return 0; -} +unsigned long get_state_synchronize_rcu(void); +unsigned long start_poll_synchronize_rcu(void); +bool poll_state_synchronize_rcu(unsigned long oldstate); static inline void cond_synchronize_rcu(unsigned long oldstate) { -- cgit v1.2.3-73-gaa49b