Strange bug inside jetty at shenandoah/jdk8u

[Roman Kennke]

I can look, this afternoon.
Yes I believe we are lacking a read barrier there.

Roman


Am 21. Dezember 2017 11:23:23 MEZ schrieb Aleksey Shipilev <shade at redhat.com>:
>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

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