RFR 8230303 : JDB hangs when running monitor command

[serguei.spitsyn at oracle.com]

Hi Ivan,

Thank you for filing the shadow bug and fixing this issue!
I've targeted the bug to 14 (please, fix me if it is wrong).

The fix looks good to me.

Do you have any plans to backport it to the earlier releases?

Thanks,
Serguei


On 9/9/19 20:41, Ivan Gerasimov wrote:
> Hello!
>
> jdb utility has a command 'monitor <command>', which allows to execute 
> the specified command every time the debuggee stops.
>
> If the <command> modifies the list of installed monitors (the simplest 
> example is 'monitor unmonitor 1'), then jdb hits a 
> ConcurrentModificationException, and hangs the debuggee.
>
> While it is questionable, if modifying the monitor list has to be 
> implemented in some specific way, it seems sensible to at least 
> prevent a hard failure.
>
> The simplest fix appears to be to use CopyOnWriteArrayList, so that an 
> immutable snapshot of the list will be traversed.
> Even if the list is modified, it wouldn't affect any iterator that 
> might exist at that moment of time.
>
> BUGURL: https://bugs.openjdk.java.net/browse/JDK-8230303
> WEBREV: http://cr.openjdk.java.net/~igerasim/8230303/00/webrev/
>
> Mach5 control build was successfully run with hs-tier7-rt, which 
> includes the new test and other jdb related tests.
>
> Would you please help review?
> Thanks in advance!
>