RFR(S) 8074312: Enable hotspot builds on 4.x Linux kernels

[David Holmes]

Thanks Mikael.

This change is now being pushed.

David

On 10/03/2015 12:07 PM, Mikael Vidstedt wrote:
>
>
> On 2015-03-09 15:03, David Holmes wrote:
>> On 9/03/2015 10:29 PM, Severin Gehwolf wrote:
>>> Hi David,
>>>
>>> Thanks for getting back to me so quickly!
>>>
>>> On Fri, 2015-03-06 at 07:00 +1000, David Holmes wrote:
>>>> Hi Severin,
>>>>
>>>> On 6/03/2015 2:27 AM, Severin Gehwolf wrote:
>>>>> Hi,
>>>>>
>>>>> Could someone please review the following one-liner to the hotspot
>>>>> build
>>>>> files. This prevents someone from building on 4.x Linux kernels
>>>>> such as
>>>>> F22, which will become available in May 2015[1].
>>>>>
>>>>> Currently, a JDK 9 build fails for me with:
>>>>>> &2 echo "*** This OS is not supported:" `uname -a`; exit 1;
>>>>> ++ uname -a
>>>>> + echo '*** This OS is not supported:' Linux f22
>>>>> 4.0.0-0.rc1.git0.1.fc22.x86_64 '#1' SMP Mon Feb 23 21:15:25 UTC
>>>>> 2015 x86_64 x86_64 x86_64 GNU/Linux
>>>>> *** This OS is not supported: Linux f22
>>>>> 4.0.0-0.rc1.git0.1.fc22.x86_64 #1 SMP Mon Feb 23 21:15:25 UTC 2015
>>>>> x86_64 x86_64 x86_64 GNU/Linux
>>>>> + exit 1
>>>>>
>>>>> The fix is to add 4 to the list of Linux kernels, similar to what was
>>>>> done for 3.x kernels in JDK-7072341.
>>>>>
>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8074312
>>>>> webrev:
>>>>> http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8074312/webrev.00/
>>>>>
>>>>> I'd also please need a sponsor for this change.
>>>>
>>>> The whole purpose of those version checks is to ensure we know there is
>>>> a reasonable level of support for a platform before we enable it -
>>>> anyone can make the change locally to try for themselves (and deal with
>>>> the consequences). Otherwise we may as well just remove the version
>>>> checks.
>>>
>>> OK. Is there some form of definition for "reasonable level of support"?
>>> Is being able to build hotspot and being able to run simple Java
>>> programs enough? For the time being I'm fine with keeping this patch
>>> local, fwiw.
>>
>> The main thing is not to have something that might cause newcomers a
>> lot of grief trying to build/run OpenJDK on their brand new system
>> XYZ. Chances are they haven't checked to see if XYZ is on the
>> supported platform list. :) So if it builds and runs basic programs
>> okay it should be okay.
>>
>>>> So I can sponsor this change for you assuming that everything does
>>>> indeed build and run fine on the Linux 4 kernel.
>>>
>>> I can build JDK 8 fine on a F22 pre-release (x86_64):
>>> $ hg paths
>>> default = http://hg.openjdk.java.net/jdk8u/jdk8u
>>> $ hg tip
>>> changeset:   1284:e532f3672f63
>>> tag:         tip
>>> user:        katleman
>>> date:        Wed Feb 25 12:59:47 2015 -0800
>>> summary:     Added tag jdk8u60-b04 for changeset d8d408861c20
>>> $
>>> ./build/linux-x86_64-normal-server-release/images/j2sdk-image/bin/java -version
>>>
>>> openjdk version "1.8.0-internal"
>>> OpenJDK Runtime Environment (build
>>> 1.8.0-internal-sgeholf_2015_03_09_12_00-b00)
>>> OpenJDK 64-Bit Server VM (build 25.60-b05, mixed mode)
>>> $ cat /etc/fedora-release
>>> Fedora release 22 (Twenty Two)
>>> $ gcc --version
>>> gcc (GCC) 5.0.0 20150226 (Red Hat 5.0.0-0.17)
>>> Copyright (C) 2015 Free Software Foundation, Inc.
>>> This is free software; see the source for copying conditions. There
>>> is NO
>>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
>>> PURPOSE.
>>>
>>> Things get trickier with JDK 9. However, I don't think they're linux
>>> kernel version related, but rather GCC 5 related.
>>
>> Interesting ...
>>
>>>> Also it seems Fedora22 will have gcc 5 so do we need build changes to
>>>> support that as well?
>>>
>>> Very likely. At this point I'm still investigating what's necessary to
>>> build JDK 9 on F22. While JDK 8 builds fine with this patch, JDK 9 has
>>> more failures which I'm currently looking into too.
>>
>> ... Is that because we have additional warnings enabled in 9 and
>> -Werror ?
>>
>>>> Are there any major new or changed features in the linux 4 kernel that
>>>> may impact the JVM?
>>>
>>> I don't think so. FWIW, calling the kernel version 4.0-rc1 instead of
>>> 3.20 is just a majority decision from the crowd on G+[1] :) The 4.x
>>> version bump does not mean there are any breaking changes. That's
>>> similar to the 3.0.0.rc-1 naming instead of calling it 2.6.40, back in
>>> May 2011[2].
>>>
>>> That begs the question: Should hotspot really be doing this kernel
>>> version check? It does make sense for OS releases that use major version
>>> bumps to communicate breaking changes. Not so much for the linux kernel
>>> these days. There is no specific check for 3.18 or 3.16 in hotspot.
>>> AFAIUI there is only a global 3.x version check. Considering that
>>> 4.0-rc1 could have been called just as well 3.20 this kernel version
>>> checking by default seems arbitrary. Thoughts?
>>
>> Yes this does seem somewhat pointless if major version number changes
>> are not based on technical changes. But I'd probably just add the 4.x
>> support and not throw it out altogether - then revisit for 5 :)
>>
>> So I can accept this patch as-is.
>>
>> Still need a second reviewer.
>
> I agree that having the check is rather arbitrary to start with, but the
> suggested change looks good!
>
> Cheers,
> Mikael
>
>>
>> David
>>
>>> Cheers,
>>> Severin
>>>
>>> [1] http://lkml.iu.edu/hypermail/linux/kernel/1502.2/04059.html
>>> [2] https://lkml.org/lkml/2011/5/29/204
>>>
>>>> Thanks,
>>>> David
>>>>
>>>>
>>>>> Thanks,
>>>>> Severin
>>>>>
>>>>> [1] http://fedoraproject.org/wiki/Releases/22/Schedule
>>>>>
>>>
>>>
>>>
>