RFR: 8178784: Revisit changes for making Serviceability Agent attach functionality optional

[Mikael Vidstedt]

Jini,

Thanks a lot for looking into this! The changes look good. One question:

Would it be possible to implement the whole opendir/readdir/closedir walk as an alternative implementation of read_thread_info in libproc_impl.c instead? Without having tried it, I think that would mean you can revert the whole ps_core.c file back to what it was before I added the #include guards, and all the special logic will instead be in libproc_impl.c.

Minor nit: there are a few places where you have a space between the function name and the parenthesis (after readdir for example), which doesn’t seem to be the style used in the rest of the places in the SA.

Cheers,
Mikael

> On May 25, 2017, at 5:26 AM, Jini George <jini.george at oracle.com> wrote:
> 
> Hi all,
> 
> Please review the changes for enabling live debugging (attaching to a process) with SA on Alpine Linux.
> 
> Webrev: http://cr.openjdk.java.net/~jgeorge/8178784/webrev.00/
> Issue: https://bugs.openjdk.java.net/browse/JDK-8178784
> 
> The crux of the changes are:
> 
> 1. To include the functions #ifdef-ed out by INCLUDE_SA_ATTACH, and to correct build errors resulting due to the inclusion of these functions.
> 2. SA on Linux uses the thread_db library for attach debugging. This library is not available on Alpine Linux. So instead of relying on thread_db, I have made changes to iterate over the list of tasks in the /proc/<pid>/task directory to find the list of threads to ptrace attach to. This enables the jhsdb commands like threads, jstack etc.
> 
> Thanks,
> Jini.
> 
>