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[5.15.y,1/2] rcu-tasks: Idle tasks on offline CPUs are in quiescent states

Message ID c56243da5c8b4451097b39468166248790f9a1de.1732237776.git.kjlx@templeofstupid.com (mailing list archive)
State New
Headers show
Series rcu-tasks: Idle tasks on offline CPUs are in quiescent states | expand

Commit Message

Krister Johansen Nov. 22, 2024, 8:47 a.m. UTC 
From: Paul E. McKenney <paulmck@kernel.org>

commit 5c9a9ca44fda41c5e82f50efced5297a9c19760d upstream

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

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.