From 3bc97a782cc8c112f64a25143452b06206364cc8 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 29 Nov 2012 16:46:05 +0800 Subject: [PATCH] srcu: Remove checks preventing offline CPUs from calling srcu_read_lock() SRCU has its own statemachine and no longer relies on normal RCU. Its read-side critical section can now be used by an offline CPU, so this commit removes the check and the comments, reverting the SRCU portion of c0d6d01b (rcu: Check for illegal use of RCU from offlined CPUs). It also makes the code match the comments in whatisRCU.txt: g. Do you need read-side critical sections that are respected even though they are in the middle of the idle loop, during user-mode execution, or on an offlined CPU? If so, SRCU is the only choice that will work for you. [ paulmck: There is at least one remaining issue, namely use of lockdep with tracing enabled. ] Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 5 ----- 1 file changed, 5 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 6eb691b08358..ae3ee39eb699 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -163,9 +163,6 @@ void srcu_barrier(struct srcu_struct *sp); * power mode. This way we can notice an extended quiescent state to * other CPUs that started a grace period. Otherwise we would delay any * grace period as long as we run in the idle task. - * - * Similarly, we avoid claiming an SRCU read lock held if the current - * CPU is offline. */ static inline int srcu_read_lock_held(struct srcu_struct *sp) { @@ -173,8 +170,6 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp) return 1; if (rcu_is_cpu_idle()) return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; return lock_is_held(&sp->dep_map); } -- 2.34.1