Integrated: 8252685: APIs that require JavaThread should take JavaThread arguments

David Holmes dholmes at openjdk.java.net
Mon May 17 04:08:28 UTC 2021


On Wed, 5 May 2021 10:16:29 GMT, David Holmes <dholmes at openjdk.org> wrote:

> Our code is littered with API's that take, or manifest, a Thread* and then assert/guarantee that it must be a JavaThread, rather than taking/manifesting a JavaThread in the first place. The main reason for this is that the TRAPS macro, used in relation to exception generation and processing, is declared as "Thread* THREAD". In practice only JavaThreads that can execute Java code can generate arbitrary exceptions, because it requires executing Java code. In other places we can get away with other kinds of threads "throwing" exceptions because they are only pre-allocated instances that require no Java code execution (e.g. OOME), or when executed by a non-JavaThread the code actually by-passes the logic would throw an exception. Such code also eventually clears the exception and reports the OOM by some other means. We have been progressively untangling these code paths and modifying TRAPS/CHECK usage so that only JavaThreads will call TRAPS methods and throw exceptions. Having done th
 at pre-work we are now ready to convert TRAPS to be "JavaThread* THREAD" and that is what this change does. The resulting changes are largely mechanical:
> 
> - declarations of "Thread* THREAD" become "JavaThread* THREAD" (where THREAD is needed for exceptions, otherwise THREAD is renamed to current)
> - methods that took a Thread* parameter that was always THREAD, now take a JavaThread* param
> - Manifestations of Thread::current() become JavaThread::current()
> - THREAD->as_Java_thread() becomes just THREAD
> - THREAD->is_Java_thread() is reworked so that THREAD is "current"
> 
> There are still places where a CompilerThread (which is a JavaThread but may not be able to execute Java code) calls a TRAPS function (primarily where OOME is possible). Fixing that would be a future RFE and may not be possible without reworking a lot of the allocation code paths.
> 
> Testing:
>  - tiers 1-8 on Linux-x64
>  - all builds in tiers 1-4
>  - tiers 1-3 on all platforms
> 
> Thanks,
> David

This pull request has now been integrated.

Changeset: 02f895c5
Author:    David Holmes <dholmes at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/02f895c5f6f6de38549337d45ed8ba4c446e9677
Stats:     535 lines in 120 files changed: 14 ins; 28 del; 493 mod

8252685: APIs that require JavaThread should take JavaThread arguments

Reviewed-by: coleenp, sspitsyn, kvn, iklam

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PR: https://git.openjdk.java.net/jdk/pull/3877


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