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



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