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Subject: Re: [PATCH v3] x86, irq: get correct available vectors for cpu disable
From: Yinghai Lu <yinghai@kernel.org>
To: Linn Crosetto <linn@hp.com>
Cc: Ingo Molnar <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Prarit Bhargava <prarit@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Mar 25, 2014 at 1:03 PM, Linn Crosetto <linn@hp.com> wrote:
> Thanks for the patch.
>
> On Tue, Jan 28, 2014 at 01:54:05PM -0800, Yinghai Lu wrote:
>> used_vectors is a bitmap for vectors that are not tracked in per_cpu
>> vector_irq.
>
> I feel like this comment (also in the code) could be misleading because vectors
> above first_system_vector are effectively not tracked in per_cpu vector_irq, but
> also may not have the bit set in used_vectors. For example, used_vectors from a
> system that I am looking at now:
>
> first_system_vector
>                 239                  255
>                   |                  |
>                   10 01000 11111 11111
>
> test_bit(240, used_vectors) does not return the correct answer to the question
> about whether the vector is tracked in per_cpu vector_irq. This leads to two
> meanings for the bitmap; for vectors less than first_system_vector whether or
> not they are tracked in per_cpu vector_irq, and for vectors above
> first_system_vector, whether or not they are in use:
>
> static inline int is_per_cpu_vector(int vector) {
>         return !test_bit(vector, used_vectors) &&
>                         vector < first_system_vector;
> }

sorry, I can not catch what you want to say.

Do you mean the change log or comment in the patch is not right?

Thanks

Yinghai