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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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