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Date: Wed, 7 Feb 2024 14:19:08 +0800
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From: Bitao Hu <yaoma@linux.alibaba.com>
Subject: Re: [PATCHv5 3/3] watchdog/softlockup: add
 SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob
To: Doug Anderson <dianders@chromium.org>
Cc: akpm@linux-foundation.org, pmladek@suse.com, kernelfans@gmail.com,
 liusong@linux.alibaba.com, linux-kernel@vger.kernel.org,
 yaoma@linux.alibaba.com
References: <20240206095902.56406-1-yaoma@linux.alibaba.com>
 <20240206095902.56406-4-yaoma@linux.alibaba.com>
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On 2024/2/7 05:42, Doug Anderson wrote:
> Hi,
> 
> On Tue, Feb 6, 2024 at 1:59 AM Bitao Hu <yaoma@linux.alibaba.com> wrote:
>>
>> The interrupt storm detection mechanism we implemented requires a
>> considerable amount of global storage space when configured for
>> the maximum number of CPUs.
>> Therefore, adding a SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob that
>> defaults to "yes" if the max number of CPUs is <= 128.
>>
>> Signed-off-by: Bitao Hu <yaoma@linux.alibaba.com>
>> ---
>>   kernel/watchdog.c |  2 +-
>>   lib/Kconfig.debug | 13 +++++++++++++
>>   2 files changed, 14 insertions(+), 1 deletion(-)
> 
> IMO this should be squashed into patch #1, though I won't insist.
Agree.
> 
> 
>> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
>> index 26dc1ad86276..1595e4a94774 100644
>> --- a/kernel/watchdog.c
>> +++ b/kernel/watchdog.c
>> @@ -338,7 +338,7 @@ __setup("watchdog_thresh=", watchdog_thresh_setup);
>>
>>   static void __lockup_detector_cleanup(void);
>>
>> -#ifdef CONFIG_IRQ_TIME_ACCOUNTING
>> +#ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM
>>   #define NUM_STATS_GROUPS       5
>>   #define NUM_STATS_PER_GROUP    4
>>   enum stats_per_group {
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 975a07f9f1cc..74002ba7c42d 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -1029,6 +1029,19 @@ config SOFTLOCKUP_DETECTOR
>>            chance to run.  The current stack trace is displayed upon
>>            detection and the system will stay locked up.
>>
>> +config SOFTLOCKUP_DETECTOR_INTR_STORM
>> +       bool "Detect Interrupt Storm in Soft Lockups"
>> +       depends on SOFTLOCKUP_DETECTOR && IRQ_TIME_ACCOUNTING
>> +       default y if NR_CPUS <= 128
>> +       help
>> +         Say Y here to enable the kernel to detect interrupt storm
>> +         during "soft lockups".
>> +
>> +         "soft lockups" can be caused by a variety of reasons. If one is caused by
>> +         an interrupt storm, then the storming interrupts will not be on the
>> +         callstack. To detect this case, it is necessary to report the CPU stats
>> +         and the interrupt counts during the "soft lockups".
> 
> It's probably not terribly important, but I notice that the other help
> text in this file is generally wrapped to 80 columns. Even though the
> kernel has relaxed the 80 column rule a bit, it still feels like this
> could easily be wrapped to 80 columns without sacrificing any
> readability.
OK.
> 
> In any case:
> 
> Reviewed-by: Douglas Anderson <dianders@chromium.org>