On Fri, 24 Sep 2021 13:13:39 GMT, Lin Zang <[email protected]> wrote:
> The root cause for crash in ZGC is that the JNIHandles are processed before
> object iteration. And ZGC would update the JNIHandles at object iteration
> with read barrier. So the crash is cause by accessing the invalid address
> which can be dummy info after zgc, and hence crash.
>
> The lock rank issue can be fixed because the related mutexes are acquired in
> safepoint. so the safepoint_check_required could be safepoint_check_always.
>
> The Epsilon issue is caused by wrong _num_dumper_thread calculated when the
> gang==NULL.
src/hotspot/share/services/heapDumper.cpp line 751:
> 749: static void before_work() {
> 750: assert(_lock == NULL, "ParDumpWriter lock must be initialized only
> once");
> 751: _lock = new (std::nothrow) PaddedMonitor(Mutex::leaf,
> "ParallelHProfWriter_lock", Mutex::_safepoint_check_always);
If you change these locks to _safepoint_check_always, you have to acquire them
without the Mutex::_no_safepoint_check flags so I don't know why you don't get
that assert.
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PR: https://git.openjdk.java.net/jdk/pull/5681
