Strange bug inside jetty at shenandoah/jdk8u

[Aleksey Shipilev]

On 12/20/2017 10:10 PM, Aleksey Shipilev wrote:
> On 12/20/2017 08:14 PM, Kirill A. Korinsky wrote:
>>> On 20 Dec 2017, at 20:16, Kirill A. Korinsky <kirill at korins.ky <mailto:kirill at korins.ky>> wrote:
>>> Hey,
>>>
>>> I made very simple test case: https://github.com/catap/jetty-shenandoah-error
>>>
>>> It is durty but it is good enough.
>>>
>>> How to reproduce:
>>> The first terminal:
>>>> mvn clean package 
>>>> docker-compose up --build
>>> The second terminal:
>>>> ab -k -c 1 -n 10000 -p request_body http://localhost:8080/test/
>>>
>>> and you should have a lot of errors likes:
>>>> server_1  | 2017-12-20 16:09:56.287:WARN:oejh.HttpParser:qtp1706377736-41: parse exception:
>>>> java.lang.IndexOutOfBoundsException: 20 for HttpChannelOverHttp at 1138214c{r=4,c=false,a=IDLE,uri=null}
> 
> Many thanks! I have successfully reproduced the failure locally with your docker-compose thing that
> brings in Fedora 27 OpenJDK build.
> 
> It seems the exact Jetty version is important. Based on your example, minimized this further to
> non-dockerized version:
>   https://github.com/shipilev/jetty-test
> 
> It seems to be the bug in Shenandoah+C1, because -Xint works fine, and -XX:-TieredCompilation works
> fine. All recent versions: sh/jdk8u, sh/jdk9, sh/jdk10 fail -- which is a good sign, and it
> simplifies the bug hunt.

Smoking gun: the failure is here in HeapByteBuffer:

    public byte get(int i) {
        return hb[ix(checkIndex(i))]; <--- !
    }

And -XX:DisableIntrinsic=_checkIndex helps. Something is wrong in LIRGenerator::do_NIOCheckIndex? I
am on the go, and my build/debug capabilities are slim. Anyone sees something completely off there?
Don't we need RB on buf read?

-Aleksey