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[16/32] rcu-tasks: Make RCU Tasks Trace stall warning handle idle offline tasks

Message ID 20220620225411.3842519-16-paulmck@kernel.org (mailing list archive)
State Mainlined
Commit f90f19da88bfe32dd1fdfd104de4c0526a3be701
Headers show
Series RCU Tasks updates for v5.20 | expand

Commit Message

Paul E. McKenney June 20, 2022, 10:53 p.m. UTC 
When a CPU is offline, its idle task can appear to be running, but it
cannot be doing anything while CPU-hotplug operations are excluded.
This commit takes advantage of that fact by making trc_check_slow_task()
check for task_curr(t) && cpu_online(task_cpu(t)), and recording
full information in that case.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.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>
---
 kernel/rcu/tasks.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 5eefbab7f2edb..64eb4d7b142e3 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1476,7 +1476,7 @@  static int trc_check_slow_task(struct task_struct *t, void *arg)
 {
 	struct trc_stall_chk_rdr *trc_rdrp = arg;
 
-	if (task_curr(t))
+	if (task_curr(t) && cpu_online(task_cpu(t)))
 		return false; // It is running, so decline to inspect it.
 	trc_rdrp->nesting = READ_ONCE(t->trc_reader_nesting);
 	trc_rdrp->ipi_to_cpu = READ_ONCE(t->trc_ipi_to_cpu);