[11] RFR(S): 8205472: Deadlock in Kitchensink when trying to print compile queues causing timeout

[Tobias Hartmann]

Hi Kim,

thanks for the review.

Best regards,
Tobias

On 09.07.2018 19:33, Kim Barrett wrote:
>> On Jul 9, 2018, at 7:58 AM, Tobias Hartmann <tobias.hartmann at oracle.com> wrote:
>>
>> Hi,
>>
>> please review the following patch:
>> https://bugs.openjdk.java.net/browse/JDK-8205472
>> http://cr.openjdk.java.net/~thartmann/8205472/webrev.00/
>>
>> When registering a compiled method in ciEnv::register_method() the compiler thread acquires the
>> MethodCompileQueue_lock and then performs a safepoint check before acquiring the Compile_lock as
>> well. If we enter a safepoint, the compiler thread is still holding the MethodCompileQueue_lock
>> while the VM thread may execute the VM_PrintCompileQueue VM operation which requires the
>> MethodCompileQueue_lock as well. We deadlock.
>>
>> This bug is very intermittent and I was only able to reproduce it by modifying the VM to always
>> enter a safepoint (see comments in JIRA). The solution is to not acquire the MethodCompileQueue_lock
>> in CompileBroker::print_compile_queues() because we only execute that code at a safepoint anyway
>> (VM_PrintCompileQueue has evaluation_mode() == _safepoint).
>>
>> Thanks,
>> Tobias
> 
> Looks good.
>