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Date:      Wed, 1 Dec 2021 09:23:29 -0500
From:      Alexander Motin <mav@FreeBSD.org>
To:        Andriy Gapon <avg@FreeBSD.org>, src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org
Subject:   Re: git: d3a8f98acbf5 - main - Make CPU children explicitly share parent unit numbers.
Message-ID:  <a656c309-1236-8ccb-6a8f-a0639f8e21f2@FreeBSD.org>
In-Reply-To: <3c211281-ce4a-3d99-ab45-4d8a6fbdbe55@FreeBSD.org>
References:  <202109250332.18P3W9UM008783@gitrepo.freebsd.org> <3c211281-ce4a-3d99-ab45-4d8a6fbdbe55@FreeBSD.org>

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Hi Andriy,

On 01.12.2021 01:39, Andriy Gapon wrote:
> On 25/09/2021 06:32, Alexander Motin wrote:
>> The branch main has been updated by mav:
>>
>> URL:
>> https://cgit.FreeBSD.org/src/commit/?id=d3a8f98acbf51e728411f10c5f179a30b9ca683c
>>
>>
>> commit d3a8f98acbf51e728411f10c5f179a30b9ca683c
>> Author:     Alexander Motin <mav@FreeBSD.org>
>> AuthorDate: 2021-09-25 03:25:46 +0000
>> Commit:     Alexander Motin <mav@FreeBSD.org>
>> CommitDate: 2021-09-25 03:31:51 +0000
>>
>>      Make CPU children explicitly share parent unit numbers.
>>           Before this device unit number match was coincidental and
>> broke if I
>>      disabled some CPU device(s).  Aside of cosmetics, for some drivers
>>      (may be considered broken) it caused talking to wrong CPUs.
>> ---
>>   sys/dev/acpica/acpi_perf.c       | 3 ++-
>>   sys/dev/acpica/acpi_throttle.c   | 3 ++-
>>   sys/dev/amdtemp/amdtemp.c        | 3 ++-
> 
> It seems that the amdtemp part of this change broke creation of
> dev.cpu.0.temperature sysctl node on my (old hardware) system.
> 
> I have 4 cores and amdtemp attaches under hostb4:
>     cpu0 pnpinfo _HID=none _UID=0 _CID=none at handle=\_PR_.P001
>       acpi_perf0
>       acpi_throttle0
>       hwpstate0
>       cpufreq0
>     cpu1 pnpinfo _HID=none _UID=0 _CID=none at handle=\_PR_.P002
>       acpi_perf1
>       hwpstate1
>     cpu2 pnpinfo _HID=none _UID=0 _CID=none at handle=\_PR_.P003
>       acpi_perf2
>       hwpstate2
>     cpu3 pnpinfo _HID=none _UID=0 _CID=none at handle=\_PR_.P004
>       acpi_perf3
>       hwpstate3
> ...
>     pcib0 pnpinfo _HID=PNP0A03 _UID=0 _CID=none at handle=\_SB_.PCI0
>       pci0
> ...
>         hostb4 pnpinfo vendor=0x1022 device=0x1203 subvendor=0x0000
> subdevice=0x0000 class=0x060000 at slot=24 function=3 dbsf=pci0:0:24:3
>           amdtemp4
> 
> 
> As you can see amdtemp attaches in a different sub-tree from cpus and
> its parent's unit number does not have any relation to any processor.

It seems you are right about the parent.  But I see that the driver does
care about its unit number when adding sysctls to CPUs.  I am not sure
that default sequential numbering is working by more than coincidence.

-- 
Alexander Motin



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