linux-kernel - Re: [PATCH v4 05/27] x86: Replace ist_enter() with nmi

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Message-ID: <20200226102031.15664d19@gandalf.local.home>
Date:   Wed, 26 Feb 2020 10:20:31 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Greg KH <gregkh@...uxfoundation.org>, gustavo@...eddedor.com,
        Thomas Gleixner <tglx@...utronix.de>, paulmck@...nel.org,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Tony Luck <tony.luck@...el.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH v4 05/27] x86: Replace ist_enter() with nmi_enter()

On Wed, 26 Feb 2020 11:27:58 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Mon, Feb 24, 2020 at 05:02:31PM -0500, Steven Rostedt wrote:
> 
> > The other is for the hwlat detector that measures the time it was in an
> > NMI, as NMIs appear as a hardware latency too.  
> 
> Yeah,.. I hate that one. But I ended up with this patch.
> 
> And yes, I know some of those notrace annotations are strictly
> unnessecary due to Makefile crap, but having them is _SO_ much easier.
> 
> ---
> Subject: x86,tracing: Robustify ftrace_nmi_enter()
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Mon Feb 24 23:40:29 CET 2020
> 
>   ftrace_nmi_enter()
>      trace_hwlat_callback()
>        trace_clock_local()
>          sched_clock()
>            paravirt_sched_clock()
>            native_sched_clock()
> 
> All must not be traced or kprobed, it will be called from do_debug()
> before the kprobe handler.
> 

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/include/asm/paravirt.h |    2 +-
>  arch/x86/kernel/tsc.c           |    7 +++++--
>  include/linux/ftrace_irq.h      |    4 ++--
>  kernel/trace/trace_clock.c      |    2 ++
>  kernel/trace/trace_hwlat.c      |    4 +++-
>  5 files changed, 13 insertions(+), 6 deletions(-)
>