From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 3/4] rcu: Do not NMI offline CPUs
Date: Wed, 6 Jan 2021 08:52:30 -0800 [thread overview]
Message-ID: <20210106165231.20441-3-paulmck@kernel.org> (raw)
In-Reply-To: <20210106165210.GA20296@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@kernel.org>
Currently, RCU CPU stall warning messages will NMI whatever CPU looks
like it is blocking either the current grace period or the grace-period
kthread. This can produce confusing output if the target CPU is offline.
This commit therefore checks for offline CPUs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tree_stall.h | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 35c1355..29cf096 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -333,9 +333,12 @@ static void rcu_dump_cpu_stacks(void)
rcu_for_each_leaf_node(rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
for_each_leaf_node_possible_cpu(rnp, cpu)
- if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
- if (!trigger_single_cpu_backtrace(cpu))
+ if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {
+ if (cpu_is_offline(cpu))
+ pr_err("Offline CPU %d blocking current GP.\n", cpu);
+ else if (!trigger_single_cpu_backtrace(cpu))
dump_cpu_task(cpu);
+ }
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
}
@@ -466,9 +469,13 @@ static void rcu_check_gp_kthread_starvation(void)
pr_err("RCU grace-period kthread stack dump:\n");
sched_show_task(gpk);
if (cpu >= 0) {
- pr_err("Stack dump where RCU grace-period kthread last ran:\n");
- if (!trigger_single_cpu_backtrace(cpu))
- dump_cpu_task(cpu);
+ if (cpu_is_offline(cpu)) {
+ pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
+ } else {
+ pr_err("Stack dump where RCU GP kthread last ran:\n");
+ if (!trigger_single_cpu_backtrace(cpu))
+ dump_cpu_task(cpu);
+ }
}
wake_up_process(gpk);
}
--
2.9.5
next prev parent reply other threads:[~2021-01-06 16:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-06 16:52 [PATCH tip/core/rcu 0/4] Stall-warning updates for v5.12 Paul E. McKenney
2021-01-06 16:52 ` [PATCH tip/core/rcu 1/4] rcu: Mark obtuse portion of stall warning as internal debug paulmck
2021-01-06 16:52 ` [PATCH tip/core/rcu 2/4] rcu: For RCU grace-period kthread starvation, dump last CPU it ran on paulmck
2021-01-06 16:52 ` paulmck [this message]
2021-01-06 16:52 ` [PATCH tip/core/rcu 4/4] rcu: Check and report missed fqs timer wakeup on RCU stall paulmck
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