From: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
The trigger_all_cpu_backtrace() function attempts to send an NMI to the
target CPU, which usually provides much better stack traces than the
dump_cpu_task() function's approach of dumping that stack from some other
CPU. So much so that most calls to dump_cpu_task() only happen after
a call to trigger_all_cpu_backtrace() has failed. And the exception to
this rule really should attempt to use trigger_all_cpu_backtrace() first.
Therefore, move the trigger_all_cpu_backtrace() invocation into
dump_cpu_task().
Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
---
kernel/rcu/tree_stall.h | 5 ++---
kernel/sched/core.c | 3 +++
kernel/smp.c | 3 +--
3 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index c3fbbcc09327f..5653560573e22 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -368,7 +368,7 @@ static void rcu_dump_cpu_stacks(void)
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))
+ else
dump_cpu_task(cpu);
}
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -511,8 +511,7 @@ static void rcu_check_gp_kthread_starvation(void)
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);
+ dump_cpu_task(cpu);
}
}
wake_up_process(gpk);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ee28253c9ac0c..e15b6a7f34f47 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11183,6 +11183,9 @@ struct cgroup_subsys cpu_cgrp_subsys = {
void dump_cpu_task(int cpu)
{
+ if (trigger_single_cpu_backtrace(cpu))
+ return;
+
pr_info("Task dump for CPU %d:\n", cpu);
sched_show_task(cpu_curr(cpu));
}
diff --git a/kernel/smp.c b/kernel/smp.c
index 650810a6f29b3..e8cdc025a046f 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -370,8 +370,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *
if (cpu >= 0) {
if (static_branch_unlikely(&csdlock_debug_extended))
csd_lock_print_extended(csd, cpu);
- if (!trigger_single_cpu_backtrace(cpu))
- dump_cpu_task(cpu);
+ dump_cpu_task(cpu);
if (!cpu_cur_csd) {
pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
arch_send_call_function_single_ipi(cpu);
--
2.31.1.189.g2e36527f23
