Re: [edk2-devel] [PATCH] MdePkg/Include: AARCH64: disable outline atomics on GCC 10.2+

["Ard Biesheuvel" <ard.biesheuvel@arm.com>]

On 5/29/20 5:18 AM, Liming Gao via groups.io wrote:
> Leif:
>   I get the point that the linux distribution default GCC version may be 10 or above. Without this fix, those developers can’t pass build edk2-stable202005. So, you think this is a critical issue to catch stable tag 202005.
> 
> Ard:
>    For this patch, I have two minor comments.
> 1) I suggest to remove Link: https://bugzilla.tianocore.org/show_bug.cgi?id=2723 from comments, because this information has been in the commit message.

I think it would be helpful to keep it but I won't insist.

> 2) Can we think __GNUC_MINOR__ is always defined? Do we need to check its value after check whether it is defined or not?
>

Yes __GNUC_MINOR__ is always defined.



> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Laszlo Ersek
> Sent: 2020年5月29日 4:03
> To: Leif Lindholm <leif@nuviainc.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>; devel@edk2.groups.io; Gao, Liming <liming.gao@intel.com>; philmd@redhat.com; mliska@suse.cz
> Subject: Re: [edk2-devel] [PATCH] MdePkg/Include: AARCH64: disable outline atomics on GCC 10.2+
> 
> On 05/28/20 12:05, Leif Lindholm wrote:
>> On Wed, May 27, 2020 at 11:12:23 +0200, Laszlo Ersek wrote:
>>>>>> Oh and I think both this patch and the assembly language
>>>>>> implementation for the atomics should be delayed after the stable
>>>>>> tag. gcc-10 is a new toolchain; so even if we don't introduce a
>>>>>> new toolchain tag such as
>>>>>> GCC10 for it, whatever we do in order to make it work, that's
>>>>>> feature enablement in my book.
>>>>>
>>>>> Works for me. By the time the next stable tag comes around, early
>>>>> adopters that are now on GCC 10.1 will likely have moved to 10.2 by
>>>>> that time, and so we may not need the assembly patch at all.
>>>>
>>>> I'm not ecstatic that we'll be releasing the first stable tag known
>>>> to break with current toolchains.
>>>
>>> If this breakage affects "current toolchains", then why was
>>> <https://bugzilla.tianocore.org/show_bug.cgi?id=2723> only reported
>>> on 2020-May-19, four days into the soft feature freeze?
>>
>> I agree the timing is crap.
>>
>>>> This isn't just affecting random crazies pulling latest toolchains
>>>> down, but people using their distro defaults (native or cross).
>>>
>>> ... "people using their distro defaults" to *not* build upstream edk2
>>> until 2020-May-19, apparently.
>>
>> Or distro defaults changing in between. I mean, we could say "Arch is
>> the same as any other distro's unstable", but I wouldn't want to go
>> down that route - I know people who use it for developing also for
>> qemu and linux.
>>
>> Argh, I also just realised the error report I saw two days after Ard's
>> intrinsics patch hit the list was not a public report. Yes, if this
>> had affected only in-development/unstable distributions, I agree this
>> isn't something we should try to deal with upstream.
>>
>>>> I don't recall if 10.1 ended up being default in F32, but it was
>>>> definitely included. In Arch, it does appear default.
>>>>
>>>> Debian/Ubuntu are unaffected in their stable releases.
>>>>
>>>> I agree it's a transitional issue, but I would really prefer to have
>>>> the intrinsics included in the release.
>>>
>>> OK, let's delay the release then, by a few days. I agree the present
>>> patch may qualify as a bugfix, but the other patch with the assembly
>>> language intrinsics doesn't. If it's really that important to have in
>>> the upcoming stable tag, then it's worth delaying the tag for. I'm
>>> fine delaying the release for it; it wouldn't be without precedent.
>>
>> I would argue it *is* a bugfix, since it only has an effect on builds
>> that would otherwise fail.
> 
> OK. That's a good argument. From my POV, feel free to merge (both patches).
> 
> Thanks
> Laszlo
> 
>> But I also do think it is important enough to delay the release if we
>> feel that is necessary.
>>
>> /
>>      Leif
>>
>>> Also, I think Ard's assembly language patch needs a Tested-by from
>>> Gary at the least (reporter of TianoCore#2723). Please reach out to
>>> him in that thread.
>>>
>>> ... More precisely, please *ping* Gary for a Tested-by in that
>>> thread, because Ard CC'd him from the start, and even credited Gary
>>> in the commit message.
>>>
>>> Thanks,
>>> Laszlo
>>>
>>
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