RFR (Preliminary): 8248194: Need better support for running SA tests on core files

[Chris Plummer]

Hi Leonid,

On 6/26/20 7:51 PM, Leonid Mesnik wrote:
> Hi
>
> The idea basically looks good. I think it just make a sense to polish it a little bit to hide "sh" usage from test and get core from OutputAnalyzer.
Ok, I'll look into both of those.
>   
> Also, there is a 'CrashApp' in ClhsdbCDSCore.java. Makes it sense to unify it with LingeredApp crasher? Currently, it uses Unsafe to crash application.
Yes, I purposely didn't not make that change. My main goal with the 
LingeredApp changes is to make it easier to make existing LingeredApp SA 
tests run on both a live process and on a core, and my main goal with 
ClhsdbCDSCore and TestJmapCore was to move the core finding code and 
ulimit code to a common location that could be reused by other tests.

Keep in mind that ClhsdbLauncher and LingeredApp are independent of each 
other. You can have a LingeredApp tests that use or don't use 
ClhsdbLauncher, and you can have a non-LingeredApp tests that use or 
don't use ClhsdbLauncher. So I didn't want to go down the path of 
changing ClhsdbCDSCore (a non LingeredApp test) to use LingeredApp. 
Likewise I did not change TestJmapCore to use LingeredApp or 
ClhsdbLauncher. Possibly there is good reason to convert some of the 
tests to start using LingeredApp and/or ClhsdbLauncher, but that should 
be done under a separate RFE.

>
> Also, crashes are used in other tests, I see some implementations in
> open/test/hotspot/jtreg/vmTestbase/vm/share/vmcrasher
I don't see vmcrasher being used by any tests. In any case, my first 
attempt went down the Unsafe path to produce a crash. The issue is that 
it forces every user of LingeredApp to include the @module for Unsafe. I 
also tried using a WhiteBox API. That was worse, also requiring every 
user of LingeredApp to include an @module, plus the tests that actually 
want to cause a crash need to @build WhiteBox.java and then do the 
classfile install. It also required additional module related hacks in 
LingeredApp. The issue with my current solution is how to get 
libLingeredApp.c to compile has not been settled on. I'm still waiting 
for an answer from the build team.
>
> So it would be nice to have some common way to crash hotspot.
I can see possibly moving the crashing code out of LingeredApp and into 
a native lib that non-LingeredApp tests can use, although that really is 
just a very small part of the changes to LingeredApp. For the most part 
the changes would look the same except you would call a different API to 
cause the crash.
>
> Leonid
>
Thanks for having a look.

Chris
>> On Jun 25, 2020, at 2:41 PM, Chris Plummer <chris.plummer at oracle.com> wrote:
>>
>> Hello,
>>
>> Please help with a preliminary review of changes to add better support for writing SA tests that work on core files:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8248194
>> http://cr.openjdk.java.net/~cjplummer/8248194/webrev.00/index.html
>>
>> As pointed out, this is a preliminary review. I suspect there will be some feedback for changes/improvements. Also, I still need to work out a final solution for how to get LingeredApp to produce a crash. What I currently have works but is somewhat of a hack w.r.t. the makefile change, so you can ignore the makefiile change for now. I'm working on a more proper solution with the build team.
>>
>> As outlined in the CR, these are the 3 main goals of this CR:
>>
>> 1. SATestUtils should include support for finding the core file. This includes parsing the output of the crashed process to locate where the core file was saved, and returning this location to the user.
>>
>> 2. SATestUtils should include support for adding the "ulimit -c unlimited" prefix to the command that will produce the core file, allowing the overriding of any lower limit so we can be sure the core file will be produced.
>>
>> 3. LingeredApp should include support for producing a core file.
>>
>> As proof of concept for these 3 changes in test library support, I'm updating the following 3 tests:
>>
>> ClhsdbCDSCore.java: Use the SATestUtils support listed above. This test does not use LingeredApp, so those improvements don't apply.
>>
>> TestJmapCore.java: Use the SATestUtils support listed above. This test does not use LingeredApp, so those improvements don't apply.
>>
>> ClhsdbFindPC.java: Use all the above features, including having LingeredApp produce a core file. This is the only test modified to start testing on core files that didn't previously do so. It still also tests on a live process.
>>
>> In the future more Clhsdb tests will be converted to work on core files in a manner similar to ClhsdbFindPC.
>>
>> The new SATestUtils code is borrowed from (more like ripped out of) ClhsdbCDSCore.java and TestJmapCore.java. They both had a lot of code dedicated to finding the core file and also applying "ulimit -c unlimitted" if necessary, but didn't do so in quite the same way. Now both these tests share code in SATestUtils.java. One thing I did drop is TestJmapCore.java use of ":KILLED_PID" in the output to help find the core file. It's no longer necessary based on the smarter core locating code I pulled from ClhsdbCDSCore.java.
>>
>> thanks,
>>
>> Chris