Printing the compiler thread when the process gets a SIGQUIT

[Jeremy Manson]

On Wed, Jan 8, 2014 at 9:41 PM, David Holmes <david.holmes at oracle.com>wrote:

> Hi Jeremy,
>
>
> On 9/01/2014 8:45 AM, Jeremy Manson wrote:
>
>> Hi folks,
>>
>> We've found it useful to have a complete list of threads when we handle
>> a SIGQUIT.  Hotspot currently prints out the VM thread and the GC
>> threads, but not the compiler threads.  Follows a patch to make it do
>> this.  Any interest, or was there a reason that compiler thread printing
>> was never implemented?
>>
>
> I think you'd need to ask the compiler folk rather than runtime folk so
> cc'ing hotspot-dev to broaden the audience - and hopefully find a sponsor
> for this. :)
>

Thanks.  I assumed it was a runtime / serviceability issue, but it being a
compiler issue also makes sense.

Basically, this is for users who get information (like CPU usage) about
threads from other sources, and are trying to figure out what those threads
do in the JVM.  They can do a SIGQUIT and find out about application
threads and VM threads and GC threads, but they then have these other,
leftover threads with no visibility.  This patch clarifies matters, and is
relatively straightforward, so it has been worthwhile having it.




> Looking at the patch you use:
>
>  _name = NEW_C_HEAP_ARRAY(char, strlen(name) + 1, mtInternal);
>
> whereas NamedThread uses:
>
> _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
>
> I don't know whether mtInternal or mtThread is the appropriate selection
> here.
>

Presumably, the sponsor (or lack thereof) would know?

 (Not sure whether I should delete the associated memory or not...  There
>> seems to be very little cleanup from compiler threads, or attempt to
>> shut them down.)
>>
>
> I'd opt for doing the free in the destructor as NamedThread does.
>
>
That was my inclination, but CompilerThread doesn't have a destructor.
 It's also been my experience that CompilerThreads are never shut down
cleanly (JVMTI Compile events continue to be sent after JVM shutdown, which
has resulted in my removing a lot of cleanup code from my own code).

Anyway, I'll wait for someone else to chime in.  (I can send the patch
again, if people on hotspot-dev didn't get it the first time.)

Jeremy
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