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rcu-tasks: Make RCU Tasks Trace stall warning handle idle offline tasks

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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>
This commit is contained in:
Paul E. McKenney 2022-05-25 09:49:26 -07:00
parent be15a16486
commit f90f19da88
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tasks.h
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@ -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);