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

["Leif Lindholm" <leif@nuviainc.com>]

Hi Liming,

Apologies if I have caused confusion (since we have been discussing
the same bug on both patches). This patch is *not* required for the
stable tag. It will be useful to include *after* the stable tag.

The intrinsics patch on its own resolves the problem (by providing
resolutions for the generated function calls), whereas *this* patch
tells GCC 10.2 or later (not yet released) not to generate those calls
in the first place.

Best Regards,

Leif

On Sat, May 30, 2020 at 15:10:07 +0000, Gao, Liming wrote:
> Ard: 
>   Lefi requests to catch this change into 202005 stable tag. I also
>   highlight this request in hard feature freeze notice mail
>   https://edk2.groups.io/g/devel/message/60421.
> 
>   If no objection before the middle of next week (2020-06-03), this
>   patch can be merged with the updated comments.
> 
> Thanks
> Liming
> > -----Original Message-----
> > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Ard Biesheuvel
> > Sent: Saturday, May 30, 2020 12:51 AM
> > To: Gao, Liming <liming.gao@intel.com>; devel@edk2.groups.io; lersek@redhat.com; Leif Lindholm <leif@nuviainc.com>
> > Cc: philmd@redhat.com; mliska@suse.cz; Kinney, Michael D <michael.d.kinney@intel.com>; afish@apple.com
> > Subject: Re: [edk2-devel] [PATCH] MdePkg/Include: AARCH64: disable outline atomics on GCC 10.2+
> > 
> > On 5/29/20 4:29 PM, Gao, Liming wrote:
> > > Ard:
> > >
> > >> -----Original Message-----
> > >> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Ard Biesheuvel
> > >> Sent: Friday, May 29, 2020 1:47 PM
> > >> To: devel@edk2.groups.io; Gao, Liming <liming.gao@intel.com>; lersek@redhat.com; Leif Lindholm <leif@nuviainc.com>
> > >> Cc: philmd@redhat.com; mliska@suse.cz
> > >> Subject: Re: [edk2-devel] [PATCH] MdePkg/Include: AARCH64: disable outline atomics on GCC 10.2+
> > >>
> > >> 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.
> > >>
> > >
> > > I agree this is useful. But, we record it in the commit message. I prefer to remove this link from source code.
> > > With this change, Reviewed-by: Liming Gao <liming.gao@intel.com>
> > >
> > 
> > 
> > Works for me.
> > 
> > I will send a v2 after the stable tag is released.
> > 
> > 
> > >>> 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
> > >>>>>
> > >>>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >
> > 
> > 
> > 
>