On Fri, 15 Apr 2022 11:45:01 GMT, Alan Bateman <[email protected]> wrote:
>> This is the implementation of JEP 425: Virtual Threads (Preview); TBD which
>> JDK version to target.
>>
>> We will refresh this PR periodically to pick up changes and fixes from the
>> loom repo.
>>
>> Most of the new mechanisms in the HotSpot VM are disabled by default and
>> require running with `--enable-preview` to enable.
>>
>> The patch has support for x64 and aarch64 on the usual operating systems
>> (Linux, macOS, and Windows). There are stubs (calling Unimplemented) for
>> zero and some of the other ports. Additional ports can be contributed via
>> PRs against the fibers branch in the loom repo.
>>
>> There are changes in many areas. To reduce notifications/mails, the labels
>> have been trimmed down for now to hotspot, serviceability and core-libs.
>> We'll add the complete set of labels when the PR is further along.
>>
>> The changes include a refresh of java.util.concurrent and ForkJoinPool from
>> Doug Lea's CVS. These changes will probably be proposed and integrated in
>> advance of this PR.
>>
>> The changes include some non-exposed and low-level infrastructure to support
>> the (in draft) JEPs for Structured Concurrency and Scope Locals. This is to
>> make life a bit easier and avoid having to separate VM changes and juggle
>> branches at this time.
>
> Alan Bateman has updated the pull request with a new target base due to a
> merge or a rebase. The incremental webrev excludes the unrelated changes
> brought in by the merge/rebase. The pull request contains five additional
> commits since the last revision:
>
> - Refresh
> - Refresh
> - Merge with jdk-19+18
> - Refresh
> - Initial push
src/java.base/share/classes/java/io/FilterInputStream.java line 233:
> 231: */
> 232: @Override
> 233: public void reset() throws IOException {
I suspect this change to remove synchronization from `mark()` and `reset()` is
intentional. The `FilterInputStream` class doesn't explain the thread safety
semantics, nor can I find commit history which would hint on why these (and
only these) methods were syncrhonized. But it looks like this synchronization
was there to serialize calls to `mark()` and `reset()` on the same
`FilterInputStream` from multiple threads. With this synchronization now
removed, subclasses or even direct usages of `FilterInputStream` would now be
impacted. Potentially outside of the JDK. Would that be a concern?
-------------
PR: https://git.openjdk.java.net/jdk/pull/8166
