linux-kernel - Re: [PATCH v2] sched/tracing: Show stacktrace for wakeup tracers

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Date:   Wed, 16 Jan 2019 16:05:06 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     mingo@...hat.com, corbet@....net, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched/tracing: Show stacktrace for wakeup tracers

On Thu, 17 Jan 2019 00:02:49 +0800
Changbin Du <changbin.du@...il.com> wrote:

> This align the behavior of wakeup tracers with irqsoff latency tracer
> that we record stacktrace at the beginning and end of waking up. The
> stacktrace shows us what is happening in the kernel.
> 
> Signed-off-by: Changbin Du <changbin.du@...il.com>

I've applied your patch, but it may be a while before you see it in
linux-next. I'll be traveling for a bit and wont be able to do the full
tests which I do before pushing to my linux-next branch.

You may see them soon in my ftrace/core branch on kernel.org.

-- Steve

> ---
>  kernel/trace/trace_sched_wakeup.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
> index da5b6e012840..f4fe7d1781e9 100644
> --- a/kernel/trace/trace_sched_wakeup.c
> +++ b/kernel/trace/trace_sched_wakeup.c
> @@ -475,6 +475,7 @@ probe_wakeup_sched_switch(void *ignore, bool preempt,
>  
>  	__trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
>  	tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
> +	__trace_stack(wakeup_trace, flags, 0, pc);
>  
>  	T0 = data->preempt_timestamp;
>  	T1 = ftrace_now(cpu);
> @@ -586,6 +587,7 @@ probe_wakeup(void *ignore, struct task_struct *p)
>  	data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);
>  	data->preempt_timestamp = ftrace_now(cpu);
>  	tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
> +	__trace_stack(wakeup_trace, flags, 0, pc);
>  
>  	/*
>  	 * We must be careful in using CALLER_ADDR2. But since wake_up