[SRU][J][PATCH 2/2] rcu-tasks: Idle tasks on offline CPUs are in quiescent states

[Krister Johansen]

From: Paul E. McKenney <paulmck at kernel.org>

Any idle task corresponding to an offline CPU is in an RCU Tasks Trace
quiescent state.  This commit causes rcu_tasks_trace_postscan() to ignore
idle tasks for offline CPUs, which it can do safely due to CPU-hotplug
operations being disabled.

Signed-off-by: Paul E. McKenney <paulmck at kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju at quicinc.com>
Cc: Eric Dumazet <edumazet at google.com>
Cc: Alexei Starovoitov <ast at kernel.org>
Cc: Andrii Nakryiko <andrii at kernel.org>
Cc: Martin KaFai Lau <kafai at fb.com>
Cc: KP Singh <kpsingh at kernel.org>
(cherry picked from commit 5c9a9ca44fda41c5e82f50efced5297a9c19760d)
Signed-off-by: Krister Johansen <kjlx at templeofstupid.com>
---
 kernel/rcu/tasks.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 5528c172570b..8648685e7dfa 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1090,7 +1090,7 @@ static void rcu_tasks_trace_postscan(struct list_head *hop)
 {
 	int cpu;
 
-	for_each_possible_cpu(cpu)
+	for_each_online_cpu(cpu)
 		rcu_tasks_trace_pertask(idle_task(cpu), hop);
 
 	// Re-enable CPU hotplug now that the tasklist scan has completed.
-- 
2.25.1