linux-kernel - Re: [PATCH] x86: add handle_irq() to allow interrupt injection

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Date:	Tue, 16 Dec 2008 21:49:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: add handle_irq() to allow interrupt injection


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Xen uses a different interrupt path, so introduce handle_irq() to
> allow interrupts to be inserted into the normal interrupt path.  This
> is handled slightly differently on 32 and 64-bit.
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> ---
> arch/x86/include/asm/irq.h |    1 +
> arch/x86/kernel/irq_32.c   |   34 +++++++++++++++++++++-------------
> arch/x86/kernel/irq_64.c   |   23 ++++++++++++++++-------
> 3 files changed, 38 insertions(+), 20 deletions(-)
>
> ===================================================================
> --- a/arch/x86/include/asm/irq.h
> +++ b/arch/x86/include/asm/irq.h
> @@ -39,6 +39,7 @@
> extern unsigned int do_IRQ(struct pt_regs *regs);
> extern void init_IRQ(void);
> extern void native_init_IRQ(void);
> +extern bool handle_irq(unsigned irq, struct pt_regs *regs);
>
> /* Interrupt vector management */
> extern DECLARE_BITMAP(used_vectors, NR_VECTORS);
> ===================================================================
> --- a/arch/x86/kernel/irq_32.c
> +++ b/arch/x86/kernel/irq_32.c
> @@ -191,6 +191,26 @@
> execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq) { return 0; }
> #endif
>
> +bool handle_irq(unsigned irq, struct pt_regs *regs)
> +{
> +	struct irq_desc *desc;
> +	int overflow;
> +
> +	overflow = check_stack_overflow();
> +
> +	desc = irq_to_desc(irq);
> +	if (unlikely(!desc))
> +		return false;
> +
> +	if (!execute_on_irq_stack(overflow, desc, irq)) {
> +		if (unlikely(overflow))
> +			print_stack_overflow();
> +		desc->handle_irq(irq, desc);
> +	}
> +
> +	return true;
> +}
> +
> /*
>  * do_IRQ handles all normal device IRQ's (the special
>  * SMP cross-CPU interrupts have their own specific
> @@ -200,31 +220,19 @@
> {
> 	struct pt_regs *old_regs;
> 	/* high bit used in ret_from_ code */
> -	int overflow;
> 	unsigned vector = ~regs->orig_ax;
> -	struct irq_desc *desc;
> 	unsigned irq;
>
> -
> 	old_regs = set_irq_regs(regs);
> 	irq_enter();
> 	irq = __get_cpu_var(vector_irq)[vector];
>
> -	overflow = check_stack_overflow();
> -
> -	desc = irq_to_desc(irq);
> -	if (unlikely(!desc)) {
> +	if (!handle_irq(irq, regs)) {
> 		printk(KERN_EMERG "%s: cannot handle IRQ %d vector %#x cpu %d\n",
> 					__func__, irq, vector, smp_processor_id());
> 		BUG();
> 	}
>
> -	if (!execute_on_irq_stack(overflow, desc, irq)) {
> -		if (unlikely(overflow))
> -			print_stack_overflow();
> -		desc->handle_irq(irq, desc);
> -	}
> -
> 	irq_exit();
> 	set_irq_regs(old_regs);
> 	return 1;
> ===================================================================
> --- a/arch/x86/kernel/irq_64.c
> +++ b/arch/x86/kernel/irq_64.c
> @@ -40,6 +40,20 @@
> #endif
> }
>
> +bool handle_irq(unsigned irq, struct pt_regs *regs)
> +{
> +	struct irq_desc *desc;
> +
> +	stack_overflow_check(regs);
> +
> +	desc = irq_to_desc(irq);
> +	if (unlikely(!desc))
> +		return false;
> +
> +	generic_handle_irq_desc(irq, desc);
> +	return true;
> +}
> +
> /*
>  * do_IRQ handles all normal device IRQ's (the special
>  * SMP cross-CPU interrupts have their own specific
> @@ -48,7 +62,6 @@
> asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
> {
> 	struct pt_regs *old_regs = set_irq_regs(regs);
> -	struct irq_desc *desc;
>
> 	/* high bit used in ret_from_ code  */
> 	unsigned vector = ~regs->orig_ax;
> @@ -56,14 +69,10 @@
>
> 	exit_idle();
> 	irq_enter();
> +
> 	irq = __get_cpu_var(vector_irq)[vector];
>
> -	stack_overflow_check(regs);
> -
> -	desc = irq_to_desc(irq);
> -	if (likely(desc))
> -		generic_handle_irq_desc(irq, desc);
> -	else {
> +	if (!handle_irq(irq, regs)) {
> 		if (!disable_apic)
> 			ack_APIC_irq();
>

the changes look rather similar. Could you please look into unifying 
irq_*.c before adding more logic to it?

	Ingo
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