RFR: 8254264: Remove redundant cross_modify_fence()

[David Holmes]

Hi Patricio,

On 15/10/2020 1:20 am, Patricio Chilano Mateo wrote:
> Hi all,
> 
> Please review the following patch that removes some uneeded uses of cross_modify_fence() in common code, in particular
> from ~ThreadBlockInVM(), ~ThreadBlockInVMWithDeadlockCheck() and java_suspend_self_with_safepoint_check(). These fences
> were added before each JavaThread had to disarm itself (8230594). After a safepoint/handshake each JavaThread will
> always call SafepointMechanism::process_if_requested_slow() when transitioning out of the safe state and will execute a
> cross_modify_fence(). Tested with mach5 tiers1-7.

As you have already done the analysis, could you show the exact call 
sequences that allow for the removal of the code as described? I'm 
trying to verify what you've stated but trying to reverse engineer the 
calling sequences is painful. :)

Thanks,
David

> Thanks,
> Patricio
> 
> -------------
> 
> Commit messages:
>   - v1
> 
> Changes: https://git.openjdk.java.net/jdk/pull/655/files
>   Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=655&range=00
>    Issue: https://bugs.openjdk.java.net/browse/JDK-8254264
>    Stats: 5 lines in 2 files changed: 0 ins; 5 del; 0 mod
>    Patch: https://git.openjdk.java.net/jdk/pull/655.diff
>    Fetch: git fetch https://git.openjdk.java.net/jdk pull/655/head:pull/655
> 
> PR: https://git.openjdk.java.net/jdk/pull/655
>