RFR: (S): JDK-8200613: SA: jstack throws UnmappedAddressException with a CDS core file

[Jini George]

Gentle reminder!

Thanks,
- Jini

On 10/9/2018 11:31 AM, Jini George wrote:
> Hello!
> 
> [Including runtime-dev since the changes are in runtime code]
> 
> Requesting reviews for:
> 
> Webrev: http://cr.openjdk.java.net/~jgeorge/8200613/webrev.01/
> BugID: https://bugs.openjdk.java.net/browse/JDK-8200613
> 
> Issue: jhsdb jstack would throw an UnmappedAddressException with a core 
> file generated from a CDS enabled java process. This is seen only with 
> Linux and with G1GC, while trying to read in data from the shared 
> strings region (the closed archive heap space). This region (which is a 
> file backed private memory region) is not dumped into the corefile for 
> Linux. This, being a heap region (and therefore being a read-write 
> region) is also not read in from the classes.jsa file in SA since only 
> the read only regions are read in while processing the core file. (The 
> expectation being that the read write regions are in the core file).
> 
> Proposed solution: The proposed solution is to have the coredump_filter 
> value corresponding to the CDS process to include bit 2 (file-backed 
> private memory), so that the file-backed private memory region also gets 
> dumped into the corefile. The proposed fix is in 
> src/hotspot/os/linux/os_linux.cpp.
> 
> Thanks,
> Jini.
>