linux-kernel - Re: [patch V4 part 1 33/36] x86,tracing: Robustify ftrace_nmi

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Date:   Fri, 8 May 2020 15:19:42 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [patch V4 part 1 33/36] x86,tracing: Robustify
 ftrace_nmi_enter()

On Tue, 05 May 2020 15:16:35 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:

> From: Peter Zijlstra <peterz@...radead.org>
> 
>   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.
> 

Looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you,


> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  arch/x86/include/asm/paravirt.h |    2 +-
>  arch/x86/kernel/tsc.c           |    4 ++--
>  include/linux/ftrace_irq.h      |    4 ++--
>  kernel/trace/trace_clock.c      |    3 ++-
>  kernel/trace/trace_hwlat.c      |    2 +-
>  5 files changed, 8 insertions(+), 7 deletions(-)
> 
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -17,7 +17,7 @@
>  #include <linux/cpumask.h>
>  #include <asm/frame.h>
>  
> -static inline unsigned long long paravirt_sched_clock(void)
> +static __always_inline unsigned long long paravirt_sched_clock(void)
>  {
>  	return PVOP_CALL0(unsigned long long, time.sched_clock);
>  }
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -207,7 +207,7 @@ static void __init cyc2ns_init_secondary
>  /*
>   * Scheduler clock - returns current time in nanosec units.
>   */
> -u64 native_sched_clock(void)
> +noinstr u64 native_sched_clock(void)
>  {
>  	if (static_branch_likely(&__use_tsc)) {
>  		u64 tsc_now = rdtsc();
> @@ -240,7 +240,7 @@ u64 native_sched_clock_from_tsc(u64 tsc)
>  /* We need to define a real function for sched_clock, to override the
>     weak default version */
>  #ifdef CONFIG_PARAVIRT
> -unsigned long long sched_clock(void)
> +noinstr unsigned long long sched_clock(void)
>  {
>  	return paravirt_sched_clock();
>  }
> --- a/include/linux/ftrace_irq.h
> +++ b/include/linux/ftrace_irq.h
> @@ -7,7 +7,7 @@ extern bool trace_hwlat_callback_enabled
>  extern void trace_hwlat_callback(bool enter);
>  #endif
>  
> -static inline void ftrace_nmi_enter(void)
> +static __always_inline void ftrace_nmi_enter(void)
>  {
>  #ifdef CONFIG_HWLAT_TRACER
>  	if (trace_hwlat_callback_enabled)
> @@ -15,7 +15,7 @@ static inline void ftrace_nmi_enter(void
>  #endif
>  }
>  
> -static inline void ftrace_nmi_exit(void)
> +static __always_inline void ftrace_nmi_exit(void)
>  {
>  #ifdef CONFIG_HWLAT_TRACER
>  	if (trace_hwlat_callback_enabled)
> --- a/kernel/trace/trace_clock.c
> +++ b/kernel/trace/trace_clock.c
> @@ -22,6 +22,7 @@
>  #include <linux/sched/clock.h>
>  #include <linux/ktime.h>
>  #include <linux/trace_clock.h>
> +#include <linux/kprobes.h>
>  
>  /*
>   * trace_clock_local(): the simplest and least coherent tracing clock.
> @@ -29,7 +30,7 @@
>   * Useful for tracing that does not cross to other CPUs nor
>   * does it go through idle events.
>   */
> -u64 notrace trace_clock_local(void)
> +u64 noinstr trace_clock_local(void)
>  {
>  	u64 clock;
>  
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -139,7 +139,7 @@ static void trace_hwlat_sample(struct hw
>  #define init_time(a, b)	(a = b)
>  #define time_u64(a)	a
>  
> -void trace_hwlat_callback(bool enter)
> +noinstr void trace_hwlat_callback(bool enter)
>  {
>  	if (smp_processor_id() != nmi_cpu)
>  		return;
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>