Unsafe: removing the monitorEnter/monitorExit/tryMonitorEnter methods

[David Holmes]

On 27/02/2014 5:30 PM, Peter Levart wrote:
> On 02/27/2014 08:29 AM, Peter Levart wrote:
>> On 02/26/2014 09:54 PM, Martin Buchholz wrote:
>>> I don't recall having added this particular wart
>>> to test/java/lang/ProcessBuilder/Basic.java, and history suggests that
>>> others did that.
>>>
>>> It does seem that being able to tell whether a java object monitor is
>>> currently locked is useful for debugging and monitoring - there
>>> should be a
>>> way to do that.
>>
>> Thread.holdsLock(Object) ?
>
> Ah, you meant to query from some other thread, right?

Right - that is the usage in Basic.java but I'm still scratching my head 
trying to understand what finding the BufferedInputStream locked is 
supposed to signify.

David
-----

> Peter
>
>>
>> Regards, Peter
>>
>>>
>>>
>>> On Wed, Feb 26, 2014 at 7:12 AM, Paul Sandoz <paul.sandoz at oracle.com>
>>> wrote:
>>>
>>>> Hi,
>>>>
>>>> Out of all the methods on Unsafe i think the
>>>> monitorEnter/monitorExit/tryMonitorEnter are the least used and are
>>>> very
>>>> strong candidates for removal.
>>>>
>>>> 99% of use-cases are supported by classes in the
>>>> java.util.concurrent.locks package.
>>>>
>>>>
>>>> Within the JDK itself it is only used in one JDK test file
>>>> test/java/lang/ProcessBuilder/Basic.java:
>>>>
>>>>                      while (unsafe.tryMonitorEnter(s)) {
>>>>                          unsafe.monitorExit(s);
>>>>                          Thread.sleep(1);
>>>>                      }
>>>>
>>>> for a test verifying an EOF is received on pending reads and it is
>>>> polling
>>>> to check when the process builder acquires the lock before
>>>> destroying the
>>>> process, presumably to avoid some sort of race condition that
>>>> occasionally
>>>> causes the test to fail.
>>>>
>>>> I believe this test as been through a number of rounds, i stared at
>>>> things
>>>> for a bit, but cannot quickly work out a replacement; i lack the
>>>> knowledge
>>>> on this area.
>>>>
>>>>
>>>> Outside of the JDK i can only find one usage of monitorExit/Enter
>>>> (according to grep code) in JBoss modules, and i believe this is
>>>> only used
>>>> on Java 1.6 to work around some limitations in class loading that were
>>>> fixed in 1.7.
>>>>
>>>>
>>>> Given such very limited use i propose to remove these methods after
>>>> having
>>>> worked out a fix for ProcessBuilder/Basic.java test.
>>>>
>>>> Paul.
>>>>
>>
>