This is a pre-requisite for moving the `HelperThread` infrastructure over from using `PRLock` and `PRCondVar` to using `js::Mutex` and `js::ConditionVariable`. Its needed because waiting on a `js::ConditionVariable` takes the `LockGuard` for the condvar's mutex as a parameter, so we need to have that accessible. When we do the conversion, `AutoLockHelperThreadState` will become derived from `LockGuard` and specialized for the helper thread state lock, and so the guard will therefore be accessible.

Also: this has the nice side effect of leveraging the type system to prove that we have taken the lock at various points, although I don't remove the now-mostly-redundant MOZ_ASSERT(HelperThreadState().isLocked()) checks in this patch. It is still technically possible that someone snuck in an unlocked the lock from under our feet (perhaps with AutoUnlockHelperThreadState) since we don't have rust's borrow checker.

FWIW: this is pretty much all mechanical.

Try push: https://treeherder.mozilla.org/#/jobs?repo=try&revision=033182f624f1

Fix bad header includes order.

New try push: https://treeherder.mozilla.org/#/jobs?repo=try&revision=fccd0fbc85f8

s/MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM/MOZ_GUARD_OBJECT_NOTIFIER_PARAM/ for AutoUnlockHelperThreadState which gained a non-guard object parameter and was causing hazard analysis builds to fail in the try push.

New try push: https://treeherder.mozilla.org/#/jobs?repo=try&revision=5b99dab57344

Comment on attachment 8766566 [details] [diff] [review] Thread `AutoLockHelperThreadState&` parameters through various `HelperThread`-related functions Review of attachment 8766566 [details] [diff] [review]: ----------------------------------------------------------------- Sorry for the churn I've requested. Should be limited to jsgc.cpp at least. ::: js/src/gc/GCRuntime.h @@ +1199,5 @@ > /* > * Concurrent sweep infrastructure. > */ > + void startTask(AutoLockHelperThreadState& locked, GCParallelTask& task, gcstats::Phase phase); > + void joinTask(AutoLockHelperThreadState& locked, GCParallelTask& task, gcstats::Phase phase); I'd like |locked| to be the last parameter here to match how we've used AutoLockGC everywhere else. ::: js/src/vm/HelperThreads.h @@ +265,5 @@ > switch (which) { > case CONSUMER: return consumerWakeup; > case PRODUCER: return producerWakeup; > case PAUSE: return pauseWakeup; > + default: MOZ_CRASH("Invalid CondVar in |whichWakeup|"); Thanks!

Pushed by nfitzgerald@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/e5ad05d9cad4 Thread `AutoLockHelperThreadState&` parameters through various `HelperThread`-related functions; r=terrence