From: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Previously, threads blocked on offlining CPUS were migrated to the
root rcu_node structure, thus requiring RCU priority boosting on this
structure. However, since commit d19fb8d1f3f6 ("rcu: Don't migrate
blocked tasks even if all corresponding CPUs offline"), RCU does not
migrate blocked tasks. Consequently, RCU no longer does RCU priority
boosting on the root rcu_node structure as of commit 1be0085b515e ("rcu:
Don't initiate RCU priority boosting on root rcu_node").
This commit therefore brings comments for the force_qs_rnp() function's
header comment in line with this new no-root-boosting reality.
Signed-off-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
[ paulmck: Also remove obsolete comment on suppressing new grace periods. ]
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e117732bcd5d..abc8512ceb5f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2548,11 +2548,11 @@ void rcu_sched_clock_irq(int user)
}
/*
- * Scan the leaf rcu_node structures, processing dyntick state for any that
- * have not yet encountered a quiescent state, using the function specified.
- * Also initiate boosting for any threads blocked on the root rcu_node.
- *
- * The caller must have suppressed start of new grace periods.
+ * Scan the leaf rcu_node structures. For each structure on which all
+ * CPUs have reported a quiescent state and on which there are tasks
+ * blocking the current grace period, initiate RCU priority boosting.
+ * Otherwise, invoke the specified function to check dyntick state for
+ * each CPU that has not yet reported a quiescent state.
*/
static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
{
--
2.17.1
