Re: [PATCH v4 08/17] watchdog/hardlockup: Style changes to watchdog_hardlockup_check() / ..._is_lockedup()

["Nicholas Piggin" <npiggin@gmail.com>]

On Fri May 5, 2023 at 8:13 AM AEST, Douglas Anderson wrote:
> These are tiny style changes:
> - Add a blank line before a "return".
> - Renames two globals to use the "watchdog_hld" prefix.

Particularly static ones don't really need the namespace prefixes.

Not sure if processed is better than warn. allcpu_dumped is better
than dumped_stacks though because the all-CPUs-dump is a particular
thing.

Other style bits seem fine.

Thanks,
Nick

> - Store processor id in "unsigned int" rather than "int".
> - Minor comment rewording.
> - Use "else" rather than extra returns since it seemed more symmetric.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> Changes in v4:
> - ("Style changes to watchdog_hardlockup_check ...") new for v4.
>
>  kernel/watchdog.c | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 2d319cdf64b9..f46669c1671d 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -89,8 +89,8 @@ __setup("nmi_watchdog=", hardlockup_panic_setup);
>  
>  static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
>  static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
> -static DEFINE_PER_CPU(bool, hard_watchdog_warn);
> -static unsigned long hardlockup_allcpu_dumped;
> +static DEFINE_PER_CPU(bool, watchdog_hardlockup_processed);
> +static unsigned long watchdog_hardlockup_dumped_stacks;
>  
>  static bool watchdog_hardlockup_is_lockedup(void)
>  {
> @@ -100,6 +100,7 @@ static bool watchdog_hardlockup_is_lockedup(void)
>  		return true;
>  
>  	__this_cpu_write(hrtimer_interrupts_saved, hrint);
> +
>  	return false;
>  }
>  
> @@ -110,21 +111,20 @@ static void watchdog_hardlockup_interrupt_count(void)
>  
>  void watchdog_hardlockup_check(struct pt_regs *regs)
>  {
> -	/* check for a hardlockup
> -	 * This is done by making sure our timer interrupt
> -	 * is incrementing.  The timer interrupt should have
> -	 * fired multiple times before we overflow'd.  If it hasn't
> +	/*
> +	 * Check for a hardlockup by making sure the CPU's timer
> +	 * interrupt is incrementing. The timer interrupt should have
> +	 * fired multiple times before we overflow'd. If it hasn't
>  	 * then this is a good indication the cpu is stuck
>  	 */
>  	if (watchdog_hardlockup_is_lockedup()) {
> -		int this_cpu = smp_processor_id();
> +		unsigned int this_cpu = smp_processor_id();
>  
> -		/* only print hardlockups once */
> -		if (__this_cpu_read(hard_watchdog_warn) == true)
> +		/* Only handle hardlockups once. */
> +		if (__this_cpu_read(watchdog_hardlockup_processed))
>  			return;
>  
> -		pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n",
> -			 this_cpu);
> +		pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", this_cpu);
>  		print_modules();
>  		print_irqtrace_events(current);
>  		if (regs)
> @@ -137,18 +137,16 @@ void watchdog_hardlockup_check(struct pt_regs *regs)
>  		 * generating interleaving traces
>  		 */
>  		if (sysctl_hardlockup_all_cpu_backtrace &&
> -				!test_and_set_bit(0, &hardlockup_allcpu_dumped))
> +		    !test_and_set_bit(0, &watchdog_hardlockup_dumped_stacks))
>  			trigger_allbutself_cpu_backtrace();
>  
>  		if (hardlockup_panic)
>  			nmi_panic(regs, "Hard LOCKUP");
>  
> -		__this_cpu_write(hard_watchdog_warn, true);
> -		return;
> +		__this_cpu_write(watchdog_hardlockup_processed, true);
> +	} else {
> +		__this_cpu_write(watchdog_hardlockup_processed, false);
>  	}
> -
> -	__this_cpu_write(hard_watchdog_warn, false);
> -	return;
>  }
>  
>  #else /* CONFIG_HARDLOCKUP_DETECTOR_PERF */
> -- 
> 2.40.1.521.gf1e218fcd8-goog