On Tue, 29 Jun 2021 21:55:04 GMT, David Holmes <[email protected]> wrote:
> Please see the JBS issue for more details, but basically we have 8 different
> kinds of internal VM JavaThreads (grouping the three types of CompilerThread
> together) that all basically duplicated the logic for initializing (preparing
> is the term we use for user-defined JavaThreads) and starting the new thread.
> This common code can be factored out into static helpers in JavaThread.
>
> This change does not look at the way the java.lang.Thread instance is created
> - that will be handled by a separate RFE.
>
> The semantics of the changes are not identical, but I don't believe there is
> any observable change in behaviour. The scope of holding the Threads_lock has
> been reduced, and we now create the JavaThread instances ("new
> XXXThread(...)") outside of the lock. As far as I can see nothing in the
> construction process needs to happen under the Threads_lock.
>
> A few of the threads use a static `_instance` field to hold a reference to
> the create JavaThread. This proved very difficult to handle, as logically the
> field would need to be updated in the middle of the new factored-out method:
> after setting all the fields but before releasing the newly started thread. I
> eventually realized that in all but one case those `_instance` fields are
> never used and so could be deleted. The one case remaining does not need to
> be set as I just described, but can be set after the thread has started, as
> the new thread does not examine it (arguably its existence is unnecessary).
>
> The trickiest changes related to the CompilerThreads, so they need particular
> scrutiny.
>
> Testing: tiers 1-3
>
> Thanks,
> David
This pull request has now been integrated.
Changeset: 4107dcf6
Author: David Holmes <[email protected]>
URL:
https://git.openjdk.java.net/jdk/commit/4107dcf6ec3fb7fd6eb0e12cdc404a2dee9ccaa1
Stats: 284 lines in 13 files changed: 65 ins; 138 del; 81 mod
8269466: Factor out the common code for initializing and starting internal VM
JavaThreads
Reviewed-by: sspitsyn, pchilanomate, dcubed, coleenp, kvn
-------------
PR: https://git.openjdk.java.net/jdk/pull/4629
