Re: [PATCH v2 3/9] crash_core: use panic_try_start() in crash_kexec()

[Jinchao Wang <wangjinchao600@gmail.com>]

On 8/29/25 10:30, Qianqiang Liu wrote:
> On Mon, Aug 25, 2025 at 10:29:31AM +0800, Jinchao Wang wrote:
>> crash_kexec() had its own code to exclude parallel execution by setting
>> panic_cpu. This is already handled by panic_try_start(). Switch to
>> panic_try_start() to remove the duplication and keep the logic consistent.
>>
>> Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
>> ---
>>   kernel/crash_core.c | 15 +++------------
>>   1 file changed, 3 insertions(+), 12 deletions(-)
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index a4ef79591eb2..bb38bbaf3a26 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -4,6 +4,7 @@
>>    * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
>>    */
>>   
>> +#include "linux/panic.h"
> 
> Can you change this line of code to #include <linux/panic.h>?
Yes, I will.
Thanks for the feedback.>
>>   #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>>   
>>   #include <linux/buildid.h>
>> @@ -143,17 +144,7 @@ STACK_FRAME_NON_STANDARD(__crash_kexec);
>>   
>>   __bpf_kfunc void crash_kexec(struct pt_regs *regs)
>>   {
>> -	int old_cpu, this_cpu;
>> -
>> -	/*
>> -	 * Only one CPU is allowed to execute the crash_kexec() code as with
>> -	 * panic().  Otherwise parallel calls of panic() and crash_kexec()
>> -	 * may stop each other.  To exclude them, we use panic_cpu here too.
>> -	 */
>> -	old_cpu = PANIC_CPU_INVALID;
>> -	this_cpu = raw_smp_processor_id();
>> -
>> -	if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) {
>> +	if (panic_try_start()) {
>>   		/* This is the 1st CPU which comes here, so go ahead. */
>>   		__crash_kexec(regs);
>>   
>> @@ -161,7 +152,7 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs)
>>   		 * Reset panic_cpu to allow another panic()/crash_kexec()
>>   		 * call.
>>   		 */
>> -		atomic_set(&panic_cpu, PANIC_CPU_INVALID);
>> +		panic_reset();
>>   	}
>>   }
>>   
>> -- 
>> 2.43.0
> 


-- 
Best regards,
Jinchao