RFR(s): 8212828: (process) Change the Process launch mechanism default on Linux to be posix_spawn

[Martin Buchholz]

Looks good to me.

It's true that these tests depending on external tools are very brittle.
In particular, strace is in the middle of a flag re-org

       -e trace=%process
       -e trace=process (deprecated)

Nevertheless, we have such tests - are they worth the maintenance burden?
My own Zombies.java test is a good example.


On Mon, Feb 11, 2019 at 10:50 AM Thomas Stüfe <thomas.stuefe at gmail.com>
wrote:

> Hi Roger, Martin,
>
> hopefully final version:
>
>
> http://cr.openjdk.java.net/~stuefe/webrevs/8213192--(process)-change-the-process-launch-mechanism-default-on-linux-to-be-posix_spawn/webrev.03/webrev/
>
> I removed the test and the changes in the test library made for the test.
> Test is just too brittle with too little nourishing value. Everything else
> is unchanged from webrev.02.
>
> Thank you, Thomas
>
>
>
> On Fri, Feb 8, 2019 at 10:38 AM Thomas Stüfe <thomas.stuefe at gmail.com>
> wrote:
>
>> Hi Roger, Martin,
>>
>> next version:
>>
>>
>> http://cr.openjdk.java.net/~stuefe/webrevs/8213192--(process)-change-the-process-launch-mechanism-default-on-linux-to-be-posix_spawn/webrev.02/webrev
>>
>> - did massage the comment in ProcessImpl.c
>> - made the test more resilient by scanning for the strace tool and by
>> silently ignoring all problems stemming from strace or the payload binary
>> not being there. The test now only fails if the forks were successully
>> executed but it does not seem to use posix-spawn.
>> - added output to the test by printing the "interesting" lines of the
>> strace output. Note that this filtering is not really sophisticated and
>> will show all thread related clone() calls as well:
>>
>> 614   [pid 12447] <... clone resumed> child_stack=0x7fe00c4baff0,
>> flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
>> parent_tidptr=0x7fe00c4bb9d0, tls=0x7fe00c4bb700,
>> child_tidptr=0x7fe00c4bb9d0) = 12452
>> 646   [pid 12447] clone(/usr/bin/strace: Process 12453 attached
>> 649   [pid 12447] <... clone resumed> child_stack=0x7fe00c3b9ff0,
>> flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
>> parent_tidptr=0x7fe00c3ba9d0, tls=0x7fe00c3ba700,
>> child_tidptr=0x7fe00c3ba9d0) = 12453
>> ....
>>
>> I am sure this could be made more intelligent but lets keep it simple for
>> now.
>>
>> - I removed the helperPath() methods Roger mentioned, they are not needed
>> anymore.
>>
>> @Martin: I like the -e signal=none -e trace=process idea but I'm not sure
>> if all versions of strace support these options. I think the strace output
>> is small enough for this small use case, some kB only.
>>
>> Cheers, Thomas
>>
>>
>>
>>
>>
>> On Thu, Feb 7, 2019 at 6:01 PM Thomas Stüfe <thomas.stuefe at gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> second version, including the updated comment in ProcessImpl.c Martin
>>> requested:
>>>
>>>
>>> http://cr.openjdk.java.net/~stuefe/webrevs/8213192--(process)-change-the-process-launch-mechanism-default-on-linux-to-be-posix_spawn/webrev.01/webrev/index.html
>>>
>>> @Roger: thanks for feeding this into your tests. I still try to get it
>>> to run thru jdk-submit, but that seems to be stuck again..
>>>
>>> Cheers, Thomas
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Feb 6, 2019 at 10:29 AM Thomas Stüfe <thomas.stuefe at gmail.com>
>>> wrote:
>>>
>>>> Hi all
>>>>
>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8213192
>>>> webrev:
>>>> http://cr.openjdk.java.net/~stuefe/webrevs/8213192--(process)-change-the-process-launch-mechanism-default-on-linux-to-be-posix_spawn/webrev.00/webrev/index.html
>>>>
>>>> (@Roger: I hope you do not mind? The bug is assigned to you but since I
>>>> happened to play around with posix_spawn I prepared this webrev. If you
>>>> rather do this change, that is fine and I will leave it to you.)
>>>>
>>>> When we added the possibility to use posix_spawn as underlying
>>>> implementation for Runtime.exec() on Linux with
>>>> https://bugs.openjdk.java.net/browse/JDK-8212828, we agreed to keep
>>>> VFORK as default until work on 13 starts. So now would be a good time to
>>>> switch the default to posix_spawn to get a good testing window. Note that
>>>> at SAP we run our VMs internally with posix_spawn as default since some
>>>> months and have not seen problems.
>>>>
>>>> As for the fix, I added a test which tests that the default is indeed
>>>> posix_spawn - not sure whether this is overdoing it though. Also, I use
>>>> strace for the test, and /bin/true, and while strace is usually available
>>>> and reachable by path resolution, I am afraid on some test machines it may
>>>> not. What do you think, should I leave the test out?
>>>>
>>>> The fix ran through all java/lang/ProcessBuilder jtreg tests ok.
>>>>
>>>> Thanks, Thomas
>>>>
>>>>