RFR: 8200626: Restore history for g1ConcurrentMarkThread.*

[Erik Helin]

On 04/04/2018 10:24 AM, Aleksey Shipilev wrote:
> On 04/04/2018 10:17 AM, Erik Helin wrote:
>> Hi all,
>>
>> this (somewhat strange) patch restores the Mercurial (hg) history for the files
>> g1ConcurrentMarkThread.{hpp, inline.hpp, cpp}. This is done by re-doing the commit (but make sure to
>> `hg mv`) and then performing a benign merge (the merge is not part of the webrev).
>>
>> I don't think the webrev will highlight that `hg mv` was properly used, but I have verified that
>> `hg log --follow src/hotspot/share/gc/g1/g1ConcurrentMarkThread.hpp` shows the entire history.
>>
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8200626
>>
>> Patch:
>> http://cr.openjdk.java.net/~ehelin/8200626/00/
> 
> Oh, nice trick.
> 
> The changes in src/hotspot/os/linux/os_linux.cpp seem to be the part of JDK-8199717 [1], should they
> really be in webrev? I guess webrev was generated against the parent that does not include that
> changeset yet? If so, I think it would be safer to generate the webrev from the merge you did
> against the "real" parent head, to check that webrev did not unroll already committed changesets.
> (Fun aside: we ran into the similar pitfall recently in Shenandoah!)

Nice catch, I included Claes' patch by mistake. Thanks for noticing this!

> "hg log -G -l 5" or something would be nice to see too.

Since this change involves so much hg metadata that is important, I 
uploaded a hg bundle:

http://cr.openjdk.java.net/~ehelin/8200626/8200626.bundle

To review the change, just:

$ # download the bundle
$ wget http://cr.openjdk.java.net/~ehelin/8200626/8200626.bundle

$ hg incoming 8200626.bundle # list the changesets in the bundle
$ hg pull -u 8200626.bundle # pull the changesets into your repository
$ hg log --graph # inspect the log

$ hg diff -r be49a19be03b:0ab2411f270d # verify that merge is benign
$ hg diff -r 8c78b974cd55 -r 0ed1370f52bb # verify my change is
                                           # identical to Leo's

Thanks,
Erik

> Thanks,
> -Aleksey
> 
> [1] http://hg.openjdk.java.net/jdk/hs/rev/89a886b7a9cf
>