Integrated: 8252406: Introduce Thread::as_Java_thread() convenience function

[David Holmes]

On Mon, 7 Sep 2020 05:56:14 GMT, David Holmes <dholmes at openjdk.org> wrote:

> This is a rather large but generally simple cleanup.
> 
> We use a lot of raw C-style casts to "(JavaThread*)" typically after checking "thread->is_Java_thread()". To simplify
> this pattern, and make the code look somewhat cleaner we introduce a convenience function Thread::as_Java_thread(),
> which asserts is_Java_thread() and returns "this" cast to "JavaThread*". A const version, as_const_Java_thread(), was
> also added to allow use in cases where we start with "const Thread *".  Summary of changes:
> - changed raw casts to use as_Java_thread()
> - removed redundant checks of is_Java_thread() as it is now done in as_Java_thread()
> - Removed checks that are checking the type system e.g.
> void foo(JavaThread* t) {
>   assert(t->is_Java_thread(), "must be")
> the only way the assert can fire is if someone deliberately bypasses the type system, and if we are going to worry
> about that then we would need asserts like this on every method that expects a JavaThread! The right place for the
> assertion is at the head of any such call chain.
> - Removed asserts that are already guaranteed in the caller.
> - Use JavaThread::current() where appropriate.
> - Use pre-existing "thread" variable where available rather than casting THREAD
> 
> Change locations found by grepping for variations of the cast syntax "(JavaThread*)" - it is possible some may have
> been missed.
> Testing: tiers 1-3
> 
> Thanks,
> David

This pull request has now been integrated.

Changeset: 976acdde
Author:    David Holmes <dholmes at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/976acdde
Stats:     476 lines in 110 files changed: 116 ins; 20 del; 340 mod

8252406: Introduce Thread::as_Java_thread() convenience function

Reviewed-by: shade, coleenp, kbarrett, dcubed

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PR: https://git.openjdk.java.net/jdk/pull/37