linux-kernel - Re: [V3 PATCH] x86: avoid calling arch_trigger_all_cpu

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Date:	Thu, 11 Nov 2010 19:23:41 +0800
From:	DDD <dongdong.deng@...driver.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	dzickus@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [V3 PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace()
 at the same time on SMP

Ingo Molnar wrote:
> Hm, another thing i noticed is that there's two of these:
> 
>>  #ifdef ARCH_HAS_NMI_WATCHDOG
>> +/* "in progress" flag of arch_trigger_all_cpu_backtrace */
>> +static unsigned long backtrace_flag;
>> +
>>  void arch_trigger_all_cpu_backtrace(void)
>>  {
>>  	int i;
>> +	unsigned long flags;
>> +
>> +	/*
>> +	 * Have to disable irq here, as the
>> +	 * arch_trigger_all_cpu_backtrace() could be
>> +	 * triggered by "spin_lock()" with irqs on.
>> +	 */
>> +	local_irq_save(flags);
> 
>> +/* "in progress" flag of arch_trigger_all_cpu_backtrace */
>> +static unsigned long backtrace_flag;
>> +
>>  void arch_trigger_all_cpu_backtrace(void)
>>  {
>>  	int i;
>> +	unsigned long flags;
>> +
>> +	/*
>> +	 * Have to disable irq here, as the
>> +	 * arch_trigger_all_cpu_backtrace() could be
>> +	 * triggered by "spin_lock()" with irqs on.
>> +	 */
>> +	local_irq_save(flags);
>> +
>> +	if (test_and_set_bit(0, &backtrace_flag))
> 
> A fair amount of code is being duplicated in two places - which is not nice. Lets 
> try to create a shared facility instead?

Yep, It is a good idea, I will try to do that. :-)

Dongdong

> 
> Thanks,
> 
> 	Ingo
> 

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