Bug 23593 – core.thread: suspendAll doesn't wait for all if current thread has detached itself

See the following for all the gory details. https://github.com/dlang/dmd/pull/14710 https://github.com/dlang/dmd/pull/14753 https://github.com/dlang/dmd/pull/14754 Essentially --- new Thread({ thread_detachThis(); GC.collect(); }).start(); --- The GC collection will call thread_suspendAll, and as the calling thread detached itself, the suspend counter will be `1` (instead of `2`) - however the counter is decremented before the entering the loop that calls sem_wait until all threads have signalled resume - meaning there's an implicit assumption that the current thread was counted - so it exits immediately rather than waiting for the main thread to respond. This means there's now a race condition between the detached thread running the GC and the main thread setting up the Thread.tstack/bstack values. If the GC scan wins, then the main thread stack won't have any live data marked.

@ibuclaw updated dlang/dmd pull request #14763 "core.thread.osthread: Don't subtract suspend counter if thread has detached itself" fixing this issue: - fix Issue 23593 - core.thread: suspendAll doesn't wait for all if current thread has detached itself. Don't subtract suspend counter if thread has detached itself. https://github.com/dlang/dmd/pull/14763

dlang/dmd pull request #14763 "core.thread.osthread: Don't subtract suspend counter if thread has detached itself" was merged into master: - 096b48eab47b9deca54fc48c96be77675eaca31b by Iain Buclaw: fix Issue 23593 - core.thread: suspendAll doesn't wait for all if current thread has detached itself. Don't subtract suspend counter if thread has detached itself. https://github.com/dlang/dmd/pull/14763