linux-kernel - Re: [PATCH v5 12/18] watchdog/hardlockup: Rename some "NMI watchdog" constants/function

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Date:   Wed, 24 May 2023 15:38:35 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        Stephane Eranian <eranian@...gle.com>, mpe@...erman.id.au,
        Tzung-Bi Shih <tzungbi@...omium.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        linuxppc-dev@...ts.ozlabs.org, Sumit Garg <sumit.garg@...aro.org>,
        npiggin@...il.com, davem@...emloft.net,
        Marc Zyngier <maz@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>, sparclinux@...r.kernel.org,
        christophe.leroy@...roup.eu,
        Catalin Marinas <catalin.marinas@....com>,
        ravi.v.shankar@...el.com, Randy Dunlap <rdunlap@...radead.org>,
        Pingfan Liu <kernelfans@...il.com>,
        Guenter Roeck <groeck@...omium.org>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Ian Rogers <irogers@...gle.com>, ito-yuichi@...itsu.com,
        ricardo.neri@...el.com, linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, Will Deacon <will@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v5 12/18] watchdog/hardlockup: Rename some "NMI watchdog"
 constants/function

On Fri 2023-05-19 10:18:36, Douglas Anderson wrote:
> Do a search and replace of:
> - NMI_WATCHDOG_ENABLED => WATCHDOG_HARDLOCKUP_ENABLED
> - SOFT_WATCHDOG_ENABLED => WATCHDOG_SOFTOCKUP_ENABLED
> - watchdog_nmi_ => watchdog_hardlockup_
> - nmi_watchdog_available => watchdog_hardlockup_available
> - nmi_watchdog_user_enabled => watchdog_hardlockup_user_enabled
> - soft_watchdog_user_enabled => watchdog_softlockup_user_enabled
> - NMI_WATCHDOG_DEFAULT => WATCHDOG_HARDLOCKUP_DEFAULT
> 
> Then update a few comments near where names were changed.
> 
> This is specifically to make it less confusing when we want to
> introduce the buddy hardlockup detector, which isn't using NMIs. As
> part of this, we sanitized a few names for consistency.
> 
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -30,17 +30,17 @@
>  static DEFINE_MUTEX(watchdog_mutex);
>  
>  #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
> -# define NMI_WATCHDOG_DEFAULT	1
> +# define WATCHDOG_HARDLOCKUP_DEFAULT	1
>  #else
> -# define NMI_WATCHDOG_DEFAULT	0
> +# define WATCHDOG_HARDLOCKUP_DEFAULT	0
>  #endif
>  
>  unsigned long __read_mostly watchdog_enabled;
>  int __read_mostly watchdog_user_enabled = 1;
> -int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
> -int __read_mostly soft_watchdog_user_enabled = 1;
> +int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
> +int __read_mostly watchdog_softlockup_user_enabled = 1;

I still see nmi_watchdog_user_enabled and soft_watchdog_user_enabled
in include/linux/nmi.h. They are declared there and also mentioned
in a comment.

It seems that they do not actually need to be declared there.
I guess that it was need for the /proc stuff. But it was
moved into kernel/watchdog.c by the commit commit dd0693fdf054f2ed37
("watchdog: move watchdog sysctl interface to watchdog.c").

>  int __read_mostly watchdog_thresh = 10;
> -static int __read_mostly nmi_watchdog_available;
> +static int __read_mostly watchdog_hardlockup_available;
>  
>  struct cpumask watchdog_cpumask __read_mostly;
>  unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);

Otherwise, I like the changes.

With the following:

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 83076bf70ce8..d14fe345eae9 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -17,8 +17,6 @@ void lockup_detector_soft_poweroff(void);
 void lockup_detector_cleanup(void);
 
 extern int watchdog_user_enabled;
-extern int nmi_watchdog_user_enabled;
-extern int soft_watchdog_user_enabled;
 extern int watchdog_thresh;
 extern unsigned long watchdog_enabled;
 
@@ -68,8 +66,8 @@ static inline void reset_hung_task_detector(void) { }
  * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
  * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
  *
- * 'watchdog_user_enabled', 'nmi_watchdog_user_enabled' and
- * 'soft_watchdog_user_enabled' are variables that are only used as an
+ * 'watchdog_user_enabled', 'watchdog_hardlockup_user_enabled' and
+ * 'watchdog_softlockup_user_enabled' are variables that are only used as an
  * 'interface' between the parameters in /proc/sys/kernel and the internal
  * state bits in 'watchdog_enabled'. The 'watchdog_thresh' variable is
  * handled differently because its value is not boolean, and the lockup

Reviewed-by: Petr Mladek <pmladek@...e.com>

Even better might be to remove the unused declaration in a separate
patch. I think that more declarations are not needed after moving
the /proc stuff into kernel/watchdog.c.

But it might also be fixed later.

Best Regards,
Petr