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sched/debug: Try trigger_single_cpu_backtrace(cpu) in dump_cpu_task()

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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@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
This commit is contained in:
Zhen Lei 2022-08-04 10:34:19 +08:00 committed by Paul E. McKenney
parent d8f3f5834f
commit e73dfe3093
3 changed files with 6 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/rcu/tree_stall.h
View File

@ -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);

3
kernel/sched/core.c
View File

@ -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));
}

3
kernel/smp.c
View File

@ -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);