Subject: Re: Subject: [PATCH 1/2] x86: get back 15 vectors

From: [email-masked] (Eric W. Biederman)
Date: Mon, 04 Jan 2010 08:18:45 -0800

Yinghai Lu <[email-masked]> writes:

This patch is wrong.

> between FIRST_EXTERNAL_VECTOR (0x20) and FIRST_DEVICE_VECTOR (0x41)
>
> for 0x20 and 0x2f, we are safe be used_vectors will prevent it to use used one.

We can not use any of 0x20 - 0x2f for ioapic irqs.  We need the entire
priority level to ensure that the irq move cleanup ipi is of a lower
priority.

> also try to reuse 0x30 to 0x3f after smp_affinity for irq[0,15] is changed to other cpu.

There may be a point with 0x30 to 0x3f as I recall when those irqs come through a legacy
pic we need to reserve those vectors on all cpus.

Eric

> Signed-off-by: Yinghai Lu <[email-masked]>

> ---
>  arch/x86/kernel/apic/io_apic.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
> +++ linux-2.6/arch/x86/kernel/apic/io_apic.c
> @@ -1162,7 +1162,8 @@ __assign_irq_vector(int irq, struct irq_
>  	 * Also, we've got to be careful not to trash gate
>  	 * 0x80, because int 0x80 is hm, kind of importantish. ;)
>  	 */
> -	static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0;
> +	static int current_vector = FIRST_EXTERNAL_VECTOR + 1;
> +	static int current_offset = 0;
>  	unsigned int old_vector;
>  	int cpu, err;
>  	cpumask_var_t tmp_mask;
> @@ -1198,7 +1199,7 @@ next:
>  		if (vector >= first_system_vector) {
>  			/* If out of vectors on large boxen, must share them. */
>  			offset = (offset + 1) % 8;
> -			vector = FIRST_DEVICE_VECTOR + offset;
> +			vector = FIRST_EXTERNAL_VECTOR + 1 + offset;
>  		}
>  		if (unlikely(current_vector == vector))
>  			continue;