linux-kernel - Re: [PATCH v2 02/22] scsi: hisi_sas: optimise the usage of hisi

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Message-ID: <CAK8P3a2skEcBm+F4CjaTGCxGfRXWsrz8zCd3sRcfQXGF=9K3tg@mail.gmail.com>
Date:   Fri, 26 May 2017 10:52:26 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     kbuild test robot <lkp@...el.com>
Cc:     John Garry <john.garry@...wei.com>, kbuild-all@...org,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        John Garry <john.garry2@...l.dcu.ie>, linuxarm@...wei.com,
        linux-scsi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xiang Chen <chenxiang66@...ilicon.com>
Subject: Re: [PATCH v2 02/22] scsi: hisi_sas: optimise the usage of hisi_hba.lock

On Fri, May 26, 2017 at 2:23 AM, kbuild test robot <lkp@...el.com> wrote:
> Hi Xiang,
>
> [auto build test ERROR on mkp-scsi/for-next]
> [also build test ERROR on v4.12-rc2 next-20170525]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url:    https://github.com/0day-ci/linux/commits/John-Garry/hisi_sas-hip08-support/20170526-011153
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next
> config: i386-allmodconfig (attached as .config)
> compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=i386
>
> All errors (new ones prefixed by >>):
>
>>> ERROR: "__umoddi3" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!

I think it must come from this line:

+       int queue_id = sas_dev->device_id % hisi_hba->queue_count;

Doing a 64-bit division seems like a rather inefficient way to
pick a queue, especially if you do it on each request. Can you
store the queue_id in sas_dev itself, or use a mask to generate
it instead?

      Arnd