The task structure's->trc_ipi_to_cpu and percpu trc_ipi_to_cpu is
used to record whether the IPI is completed, if the percpu trc_ipi_to_cpu
is true and task structure's->trc_ipi_to_cpu is non-negative value,
indicates that IPI is not completed, if the IPI is unresponsive for
along time for some reason, there will be a possibility of causing
RCU-Tasks trace stall. this commit therefore allow dump late IPI CPU
stacks to show the path that current CPU is executing.
Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
---
In the real world, the IPI delay will be very small, so the
probability of triggering dump_cpu_stack() may be very low,
so if I makes noise, please ignore it.
kernel/rcu/tasks.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index baf7ec178155..85237fc1d0f0 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1658,8 +1658,13 @@ static void show_stalled_ipi_trace(void)
int cpu;
for_each_possible_cpu(cpu)
- if (per_cpu(trc_ipi_to_cpu, cpu))
+ if (per_cpu(trc_ipi_to_cpu, cpu)) {
pr_alert("\tIPI outstanding to CPU %d\n", cpu);
+ if (cpu_is_offline(cpu))
+ pr_alert("offline CPU %d blocking gp\n", cpu);
+ else
+ dump_cpu_task(cpu);
+ }
}
/* Do one scan of the holdout list. */
--
2.25.1
