Re: [PATCH v3] x86, irq: get correct available vectors for cpu disable

[Linn Crosetto]

On Wed, Mar 26, 2014 at 10:04:52AM -0700, Yinghai Lu wrote:
> On Wed, Mar 26, 2014 at 9:50 AM, Linn Crosetto <linn@xxxxxx> wrote:
> > On Tue, Mar 25, 2014 at 05:18:53PM -0700, Yinghai Lu wrote:
> >
> > Just noting that not all bits above first_system_vector are set in the bitmap,
> > so the comment in asm/desc.h and the change log could be misleading:
> >
> > /* used_vectors is BITMAP for irq is not managed by percpu vector_irq */
> >
> 
> Do you mean some vector that is neither used by percpu_vector_irq nor
> system_vector
> after first_system_vector ?

Yes, that is the case. In my previous example, first_system_vector is 239, but
test_bit(240, used_vectors) would return unset, though it cannot be used by
percpu vector_irq. If it marked all vectors unusable by percpu vector_irq, then
all bits above first_system_vector would be set.

> Anyway if bit is set in used_vectors, that vector can not be used by
> percpu vector_irq.
> 
> so that statement looks still right.
> 
> Feel free to suggest right comment or changelog.

The following might be more accurate:

/* 
 * The used_vectors BITMAP marks IRQs not managed by percpu vector_irq, below
 * first_system_vector. Vectors above first_system_vector are not managed by
 * percpu vector_irq.
 */
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