linux-kernel - Re: [patch 01/29] hardlockup_detector: Provide interface to stop/restart perf events

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Date:   Wed, 6 Sep 2017 18:14:06 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Nicholas Piggin <npiggin@...il.com>,
        Don Zickus <dzickus@...hat.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Ulrich Obergfell <uobergfe@...hat.com>
Subject: Re: [patch 01/29] hardlockup_detector: Provide interface to
 stop/restart perf events

On Thu, Aug 31, 2017 at 09:15:59AM +0200, Thomas Gleixner wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> 
> Provide a interface to stop and restart perf NMI watchdog events on all

"an interface"

> CPUs. This is only useable during init and especially for handling the perf

"usable"

> HT bug on Intel machines. It's safe to use it this way as nothing can
> start/stop the NMI watchdog in parallel.
> 
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  include/linux/nmi.h   |    4 ++++
>  kernel/watchdog_hld.c |   41 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 45 insertions(+)
> 
> --- a/include/linux/nmi.h
> +++ b/include/linux/nmi.h
> @@ -75,7 +75,11 @@ static inline void hardlockup_detector_d
>  
>  #if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
>  extern void arch_touch_nmi_watchdog(void);
> +extern void hardlockup_detector_perf_stop(void);
> +extern void hardlockup_detector_perf_restart(void);
>  #else
> +static inline void hardlockup_detector_perf_stop(void) { }
> +static inline void hardlockup_detector_perf_restart(void) { }
>  #if !defined(CONFIG_HAVE_NMI_WATCHDOG)
>  static inline void arch_touch_nmi_watchdog(void) {}
>  #endif
> --- a/kernel/watchdog_hld.c
> +++ b/kernel/watchdog_hld.c
> @@ -261,3 +261,44 @@ void watchdog_nmi_disable(unsigned int c
>  			firstcpu_err = 0;
>  	}
>  }
> +
> +/**
> + * hardlockup_detector_perf_stop - Globally stop watchdog events
> + *
> + * Special interface for x86 to handle the perf HT bug.
> + */
> +void __init hardlockup_detector_perf_stop(void)

Right, can we make those naming prefixes shorter? Something like
hld_perf_stop() and hld_perf_restart()?

File has already "hld" in the name so ...

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.