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rcu: Do not NMI offline CPUs 

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>
This commit is contained in:
Paul E. McKenney 2020-11-12 12:19:47 -08:00
parent 243027a3c8
commit 725969ac11
1 changed files with 12 additions and 5 deletions
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17
kernel/rcu/tree_stall.h
View File

@ -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);
}