RFR: 8151526: Print -Xlog configuration in the hs_err_pid file

[Marcus Larsson]

Hi,

On 03/31/2016 08:08 PM, Max Ockner wrote:
> (Replies in line)
>
> On 3/30/2016 9:31 AM, Thomas Stüfe wrote:
>> Hi Max,
>>
>> Disclaimer: not a (R)eviewer.
>>
>> Do we really need a list of all tags and all decorators?
>>
> Just going by what we currently put in the hs_err file, I think this 
> may be the first "Do we really need" we've ever asked for this type of 
> change.
>
> All joking aside, I think it is a good idea to direct users toward 
> proper UL usage whenever we have a chance.
>
>> Also: I assume what you print is the Log state as it is at the time 
>> the hs-err file is printed. If logging was enabled/changed during 
>> lifetime of the VM, e.g. with jcmd, would it be possible to see that? 
>> At least a warning if logging was not enabled from the start on.
>>
> Would it be possible? Yes, but I think this would require a framework 
> change. It does not look like any marks are made when the 
> LogConfiguration changes during runtime, and we would need to record 
> that in order to know what to print when we dump into hs_err.

Yes, this would required the framework to keep some sort of log of 
configuration changes. Is there value in knowing that the log 
configuration changed since startup?

>
> Thanks,
> Max
>> Kind Regards, Thomas
>>
>>
>>
>>
>> On Tue, Mar 29, 2016 at 9:00 PM, Max Ockner <max.ockner at oracle.com 
>> <mailto:max.ockner at oracle.com>> wrote:
>>
>>     Hello,
>>     Please review another Unified Logging change. They are almost
>>     done, and we are serious this time.
>>
>>     bug: https://bugs.openjdk.java.net/browse/JDK-8151526
>>     webrev: http://cr.openjdk.java.net/~mockner/8151526.01/
>>     <http://cr.openjdk.java.net/%7Emockner/8151526.01/>
>>

LogConfiguration::describe() takes the ConfigurationLock, which might be 
problematic for the error handler. I suppose the error handler could 
potentially deadlock if its thread already holds the lock. Unsure how to 
resolve this, because skipping to take the lock means that we might 
crash due to another thread changing the configuration as we read it.

Thanks,
Marcus

>>
>>     The logging configuration is now printed in each hs_err file. The
>>     output is the same as you would see from -Xlog:logging=trace and
>>     it is obtained from LogConfiguration::describe().
>>
>>     Below is a sample of the hs_err contents. The Logging info is
>>     printed after VM Arguments and Whitebox, and before Environment
>>     Variables.
>>
>>     VM Arguments:
>>     java_command: Kaboom
>>     java_class_path (initial): .
>>     Launcher Type: SUN_STANDARD
>>
>>     Logging:
>>     Available log levels: off, trace, debug, info, warning, error
>>     Available log decorators: time (t), uptime (u), timemillis (tm),
>>     uptimemillis (um), timenanos (tn), uptimenanos (un), hostname
>>     (hn), pid (p), tid (ti), level (l), tags (tg)
>>     Available log tags: alloc, age, barrier, biasedlocking, bot,
>>     census, classhisto, classresolve, classinit, classload,
>>     classloaderdata, classunload, classpath, compaction, cpu, cset,
>>     defaultmethods, ergo, exceptions, exit, freelist, gc, heap,
>>     humongous, ihop, itables, jni, liveness, logging, marking,
>>     metaspace, modules, monitorinflation, os, phases, plab,
>>     promotion, preorder, protectiondomain, ref, refine, region,
>>     remset, safepoint, safepointcleanup, scavenge, scrub, stacktrace,
>>     start, startuptime, state, stats, stringdedup, stringtable,
>>     survivor, sweep, task, thread, tlab, time, verboseverification,
>>     verify, vmoperation, vtables
>>     Log output configuration:
>>     #0: stdout all=off uptime,level,tags,
>>     #1: stderr all=warning uptime,level,tags,
>>
>>     Environment Variables:
>>     JAVA_HOME=/scratch/mockner/UL/8151526/build/linux-x86_64-normal-server-fastdebug/images/jdk
>>     PATH=/home/mockner/tools/webrev:/bin:/usr/bin:/usr/local/bin:/usr/sbin:/home/mockner/bin:/home/mockner/linux/bin
>>     SHELL=/bin/bash
>>     OS=Linux
>>
>>
>