RFR: 8211956: AppCDS crashes for some uses with JRuby

[Jiangli Zhou]

Thanks for the review. In jdk 12, there is already an assert in 
space_at(), which is called by FileMapInfo::verify_region_checksum(). 
I'll add assert when back porting to jdk 11.

assert(i >= 0 && i < NUM_CDS_REGIONS, "invalid region");

With 12, the assert is hit when running into the bug:

# after -XX: or in .hotspotrc: SuppressErrorAt=/filemap.hpp:166
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error 
(/export/users/jiangli/jdk12/open/src/hotspot/share/memory/filemap.hpp:166), 
pid=23161, tid=23162
# assert(i >= 0 && i < 9) failed: invalid region
#
# JRE version: (12.0) (slowdebug build )
# Java VM: Java HotSpot(TM) 64-Bit Server VM (slowdebug 
12-internal+0-2018-10-09-0504378.jianzhou.jdk12, mixed mode, aot, 
sharing, tiered, compressed oops, g1 gc, linux-amd64)
# Core dump will be written. Default location: Core dumps may be 
processed with "/usr/share/apport/apport %p %s %c" (or dumping to 
/export/users/jiangli/jruby/jruby-startup-master/core.23161)
#
# An error report file with more information is saved as:
# /export/users/jiangli/jruby/jruby-startup-master/hs_err_pid23161.log
#
# If you would like to submit a bug report, please visit:
# http://bugreport.java.com/bugreport/crash.jsp
#

Thanks,
Jiangli

On 10/14/18 8:47 PM, Ioi Lam wrote:
> Hi Jiangli,
>
> Looks good. Maybe also add an assert on the region index inside 
> verify_region_checksum()? No need to send new webrev.
>
> Thanks
>
> - Ioi
>
>
> On 10/12/18 5:17 PM, Jiangli Zhou wrote:
>> Please review the following trivial fix in 
>> FileMapInfo::verify_mapped_heap_regions:
>>
>> webrev: http://cr.openjdk.java.net/~jiangli/8211956/webrev.00/
>> bug: https://bugs.openjdk.java.net/browse/JDK-8211956
>>
>> This issue was reported by Charles Nutter when using AppCDS with 
>> Jruby. The failure happens when large number of classes (>7000) and 
>> java objects (mirror objects of archived classes) are archived. With 
>> 'oa1' (open archive heap space 1) also being used, the runtime 
>> crashes during mapping/validating the archive heap regions. 
>> FileMapInfo::verify_mapped_heap_regions accesses beyond the end of 
>> archived space array and reads in garbage, which causes the crash. 
>> The fix is to make sure FileMapInfo::verify_mapped_heap_regions only 
>> verifies 'num' of spaces. Thanks Charles for reporting the issue and 
>> Claes for forwarding. Also thanks Ioi for jumping in and helping 
>> investigation.
>>
>> I've also created a follow up RFE, JDK-8212149 for creating a stress 
>> test for archive heap regions with large number of archived heap 
>> objects.
>>
>> Verified the fix with jruby. Running tier1-tier5.
>>
>> Thanks,
>>
>> Jiangli
>