[9] RFR(XS): 8042570: Excessive number of tests timing out on nightly testing due to fix for 8040798

[Albert]

On 05/08/2014 05:05 AM, David Holmes wrote:
> On 7/05/2014 9:34 PM, Albert wrote:
>> Hi,
>>
>> could I get reviews for this patch?
>>
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8042570
>>
>> Problem:
>> The fix of JDK-8040798 introduced a lock (MethodCompileQueue_lock) prior
>> to accessing the compilation queues
>> of C1 and C2 in CompileBroker::mark_on_stack().
>> CompileBroker::mark_on_stack() is executed at a safepoint.
>> The locks that I introduced can cause the deadlock, since the
>> MethodCompileQueue_lock lock is held at a safepoint
>> that is reached from ciEnv::register_method(). This causes the deadlock.
>
> This begs the question why you thought locking was necessary then and 
> you no longer think it necessary now?
>
I introduced the lock in the first place, since compilation queues are 
accessed by multiple threads and CompileQueue::mark_on_stack()
modifies elements of the queue without acquiring a lock. However, I did 
not realize that CompileQueue::mark_on_stack() is executed at
a safepoint.

Best,
Albert
> David
> -----
>
>> I verified that deadlock happens as described above using the
>> Redefine_v52_strict_invoke_redefine test.
>>
>> Solution:
>> Remove locks in CompileBroker::mark_on_stack().
>>
>> Testing:
>> Failing test cases.
>>
>> webrev:
>> http://cr.openjdk.java.net/~anoll/8042570/webrev.00/
>>
>> Many thanks in advance and sorry having introduced this bug,
>> Albert