Re: [PATCH 2/9] irq-remove: arch non-trivial

[Jeff Garzik <jeff@garzik.org>]

Jeremy Fitzhardinge wrote:
> Jeff Garzik wrote:
>> commit 8d45690dd90b18daaa21b981ab20caf393220bf0
>> Author: Jeff Garzik <jeff@garzik.org>
>> Date:   Fri Oct 19 00:46:23 2007 -0400
>>
>>     [IRQ ARG REMOVAL] various non-trivial arch updates
>>
>>  arch/x86/kernel/vm86_32.c     |    3 ++-
>>  include/asm-x86/irq_regs_32.h |   25 +++++++++++++++++++++++++
>>  2 files changed, 27 insertions(+), 1 deletion(-)
>>
>> 8d45690dd90b18daaa21b981ab20caf393220bf0
>> diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
>> index 157e4be..18aae9e 100644
>> --- a/arch/x86/kernel/vm86_32.c
>> +++ b/arch/x86/kernel/vm86_32.c
>> @@ -739,10 +739,11 @@ static int irqbits;
>>  	| (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
>>  	| (1 << SIGUNUSED) )
>>  	
>> -static irqreturn_t irq_handler(int intno, void *dev_id)
>> +static irqreturn_t irq_handler(void *dev_id)
>>  {
>>  	int irq_bit;
>>  	unsigned long flags;
>> +	unsigned int intno = get_irqfunc_irq();
>>  
>>  	spin_lock_irqsave(&irqbits_lock, flags);	
>>  	irq_bit = 1 << intno;
>> diff --git a/include/asm-x86/irq_regs_32.h b/include/asm-x86/irq_regs_32.h
>> index 3368b20..68a531d 100644
>> --- a/include/asm-x86/irq_regs_32.h
>> +++ b/include/asm-x86/irq_regs_32.h
>> @@ -26,4 +26,29 @@ static inline struct pt_regs *set_irq_regs(struct pt_regs *new_regs)
>>  	return old_regs;
>>  }
>>  
>> +DECLARE_PER_CPU(unsigned int, __irqfunc_irqs);
>> +
>> +static inline unsigned int get_irqfunc_irq(void)
>> +{
>> +	return __get_cpu_var(__irqfunc_irqs);
>> +}
>> +
>> +#if 0
>> +static inline unsigned int set_irqfunc_irq(unsigned int new_irq)
>> +{
>> +	unsigned int old_irq, *pirq = &__get_cpu_var(__irqfunc_irqs);
>> +
>> +	old_irq = *pirq;
>> +	*pirq = new_irq;
>> +	return old_irq;
>> +}
>> +#else
>> +static inline void set_irqfunc_irq(unsigned int new_irq)
>> +{
>> +	int *pirq = &__get_cpu_var(__irqfunc_irqs);
>> +
>> +	*pirq = new_irq;
>>   
> 
> x86_write_percpu(__irqfunc_irqs, new_irq) would be slightly more
> efficient here.  Any why the pointer anyway?

Answering the latter question -- that's the way 
include/asm-generic/irq_regs.h was written, and I simply followed their 
lead.

One attribute of this method is to avoid preemption, which is probably 
necessary in the bowels of irq handling.

	Jeff