RFR: 8292302: Windows GetLastError value overwritten by ThreadLocalStorage::thread

[Kevin Walls]

On Fri, 2 Sep 2022 20:33:37 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> This is an MR which partially reverts JDK-8289091 such that JavaThread::threadObj() does not call Thread::current().
>> 
>> A JVMTI operation could call threadObj() and clear the Windows GetLastError value.
>> 
>> Partial, because I haven't reverted changes in JavaThread::print_on_error(), they aren't connected to the problems seen.
>
> src/hotspot/share/runtime/javaThread.cpp line 165:
> 
>> 163: oop JavaThread::threadObj() const {
>> 164:   // Using Thread::current_or_null_safe() here risks that calling threadObj() can
>> 165:   // overwrite a native thread local, e.g. JVMTI operations clearing GetLastError on Windows.
> 
> Suggestion:
> 
> // Ideally we would verify the current thread is oop_safe when this is called, but as we can
> // be called from a signal handler we would have to use Thread::current_or_null_safe(). That
> // has overhead and also interacts poorly with GetLastError on Windows due to the use of TLS.
> // Instead callers must verify oop safe access.

Thanks David, will update comment and check Dan is OK with this.

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PR: https://git.openjdk.org/jdk/pull/10147