On Fri, 15 Oct 2021 18:20:12 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
>> Daniel D. Daugherty has updated the pull request incrementally with one
>> additional commit since the last revision:
>>
>> 8249004.cr1.patch
>
> src/hotspot/share/runtime/handshake.cpp line 358:
>
>> 356: bool target_is_dead = false;
>> 357: if (target == nullptr) {
>> 358: target_is_dead = true;
>
> Why would you pass a NULL target thread to Handshake::execute? Why would the
> caller not check if the target is dead?
The `NULL` target thread being passed in is actually handled by the baseline
code:
ThreadsListHandle tlh;
if (tlh.includes(target)) {
`tlh.includes(target)` returns `false` when `target` is `NULL/nullptr`.
I just made the already handled situation more explicit.
> Why would the caller not check if the target is dead?
Hmmm... It's hard for me to answer that question since I didn't write
the original code. The test code that calls `WB_HandshakeWalkStack()`
or `WB_AsyncHandshakeWalkStack()` can call those functions with
a `thread_handle` that translates into a `thread_oop` that returns a
`NULL` `JavaThread*`.
See the comment that I added to `WB_AsyncHandshakeWalkStack()` above.
> src/hotspot/share/runtime/thread.cpp line 497:
>
>> 495: // placement somewhere in the calling context.
>> 496: bool Thread::is_JavaThread_protected_by_my_ThreadsList(const
>> JavaThread* p) {
>> 497: Thread* current_thread = Thread::current();
>
> Shouldn't you call this on the current thread as "this" argument?
I modeled the new check after the existing:
bool Thread::is_JavaThread_protected(const JavaThread* p) {
which is also a static function.
-------------
PR: https://git.openjdk.java.net/jdk/pull/4677
