linux-kernel - Re: [PATCH v2 2/2] x86/panic: Add x86_panic_handler as default post-panic behavior

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Message-ID: <575bdc12-be65-42a9-9581-e2a31e6ce810@gmail.com>
Date: Tue, 29 Apr 2025 09:25:35 -0500
From: Carlos Bilbao <carlos.bilbao.osdev@...il.com>
To: Sean Christopherson <seanjc@...gle.com>, carlos.bilbao@...nel.org
Cc: tglx@...utronix.de, jan.glauber@...il.com, bilbao@...edu,
 pmladek@...e.com, akpm@...ux-foundation.org, jani.nikula@...el.com,
 linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
 takakura@...inux.co.jp, john.ogness@...utronix.de
Subject: Re: [PATCH v2 2/2] x86/panic: Add x86_panic_handler as default
 post-panic behavior

Hello,

On 4/29/25 09:57, Sean Christopherson wrote:
> On Mon, Apr 28, 2025, carlos.bilbao@...nel.org wrote:
>> From: Carlos Bilbao <carlos.bilbao@...nel.org>
>>
>> Add function x86_panic_handler() as the default behavior for x86 for
>> post-panic stage via panic_set_handling(). Instead of busy-wait loop, it
>> will halt if there's no console to save CPU cycles.
>>
>> Signed-off-by: Carlos Bilbao (DigitalOcean) <carlos.bilbao@...nel.org>
>> ---
>>  arch/x86/kernel/setup.c | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index 9d2a13b37833..3bfef55e9adb 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -16,6 +16,7 @@
>>  #include <linux/initrd.h>
>>  #include <linux/iscsi_ibft.h>
>>  #include <linux/memblock.h>
>> +#include <linux/panic.h>
>>  #include <linux/panic_notifier.h>
>>  #include <linux/pci.h>
>>  #include <linux/root_dev.h>
>> @@ -837,6 +838,15 @@ static void __init x86_report_nx(void)
>>  	}
>>  }
>>  
>> +
> Spurious newline.
>
>> +static void x86_panic_handler(void)
>> +{
>> +	if (console_trylock()) {
> A comment here would be very helpful.  Even with the changelog saying "if there's
> no console", as an unfamiliar reader of console code, I have zero idea why being
> able to lock the console is an effective test for no console.


Agree, will fix in v3.


>
>> +		console_unlock();
>> +		safe_halt();
>> +	}
>> +}


Thanks,

Carlos