From f90f19da88bfe32dd1fdfd104de4c0526a3be701 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 25 May 2022 09:49:26 -0700 Subject: [PATCH] rcu-tasks: Make RCU Tasks Trace stall warning handle idle offline tasks 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 Cc: Peter Zijlstra Cc: Neeraj Upadhyay Cc: Eric Dumazet Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: KP Singh --- 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 5eefbab7f2ed..64eb4d7b142e 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); -- 2.20.1