From 26ece8ef6eca97f19eb5ad5186b8c1a29ab25d76 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 28 Jan 2016 18:48:37 -0800 Subject: rcu: Fix synchronize_rcu_expedited() header comment This commit brings the synchronize_rcu_expedited() function's header comment into line with the new implementation. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) (limited to 'kernel/rcu') diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index efdf7b61ce12..a2ac2628ef8e 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -722,13 +722,19 @@ static void sync_rcu_exp_handler(void *info) * synchronize_rcu_expedited - Brute-force RCU grace period * * Wait for an RCU-preempt grace period, but expedite it. The basic - * idea is to invoke synchronize_sched_expedited() to push all the tasks to - * the ->blkd_tasks lists and wait for this list to drain. This consumes - * significant time on all CPUs and is unfriendly to real-time workloads, - * so is thus not recommended for any sort of common-case code. - * In fact, if you are using synchronize_rcu_expedited() in a loop, - * please restructure your code to batch your updates, and then Use a - * single synchronize_rcu() instead. + * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler + * checks whether the CPU is in an RCU-preempt critical section, and + * if so, it sets a flag that causes the outermost rcu_read_unlock() + * to report the quiescent state. On the other hand, if the CPU is + * not in an RCU read-side critical section, the IPI handler reports + * the quiescent state immediately. + * + * Although this is a greate improvement over previous expedited + * implementations, it is still unfriendly to real-time workloads, so is + * thus not recommended for any sort of common-case code. In fact, if + * you are using synchronize_rcu_expedited() in a loop, please restructure + * your code to batch your updates, and then Use a single synchronize_rcu() + * instead. */ void synchronize_rcu_expedited(void) { -- cgit v1.2.3-59-g8ed1b