Unsafe: removing the monitorEnter/monitorExit/tryMonitorEnter methods

[Brian Goetz]

Seems like a symbolic victory, at least :)  It's less unsafe than some 
unsafe methods (you can use it to create a DoS but not to violate safety 
constraints like bounds checking or pointer casting) but its a start!

On 2/26/2014 10:12 AM, Paul Sandoz 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.
>