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Diffstat (limited to '')
| -rw-r--r-- | js/src/vm/OffThreadPromiseRuntimeState.cpp | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/js/src/vm/OffThreadPromiseRuntimeState.cpp b/js/src/vm/OffThreadPromiseRuntimeState.cpp new file mode 100644 index 0000000000..83e9b7de3e --- /dev/null +++ b/js/src/vm/OffThreadPromiseRuntimeState.cpp @@ -0,0 +1,298 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=2 et sw=2 tw=80: + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "vm/OffThreadPromiseRuntimeState.h" + +#include "mozilla/Assertions.h" // MOZ_ASSERT{,_IF} + +#include <utility> // mozilla::Swap + +#include "jspubtd.h" // js::CurrentThreadCanAccessRuntime + +#include "js/AllocPolicy.h" // js::ReportOutOfMemory +#include "js/HeapAPI.h" // JS::shadow::Zone +#include "js/Promise.h" // JS::Dispatchable, JS::DispatchToEventLoopCallback +#include "js/Utility.h" // js_delete, js::AutoEnterOOMUnsafeRegion +#include "threading/ProtectedData.h" // js::UnprotectedData +#include "vm/JSContext.h" // JSContext +#include "vm/PromiseObject.h" // js::PromiseObject +#include "vm/Realm.h" // js::AutoRealm +#include "vm/Runtime.h" // JSRuntime + +#include "vm/Realm-inl.h" // js::AutoRealm::AutoRealm + +using JS::Handle; + +using js::OffThreadPromiseRuntimeState; +using js::OffThreadPromiseTask; + +OffThreadPromiseTask::OffThreadPromiseTask(JSContext* cx, + JS::Handle<PromiseObject*> promise) + : runtime_(cx->runtime()), promise_(cx, promise), registered_(false) { + MOZ_ASSERT(runtime_ == promise_->zone()->runtimeFromMainThread()); + MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_)); + MOZ_ASSERT(cx->runtime()->offThreadPromiseState.ref().initialized()); +} + +OffThreadPromiseTask::~OffThreadPromiseTask() { + MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_)); + + OffThreadPromiseRuntimeState& state = runtime_->offThreadPromiseState.ref(); + MOZ_ASSERT(state.initialized()); + + if (registered_) { + unregister(state); + } +} + +bool OffThreadPromiseTask::init(JSContext* cx) { + MOZ_ASSERT(cx->runtime() == runtime_); + MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_)); + + OffThreadPromiseRuntimeState& state = runtime_->offThreadPromiseState.ref(); + MOZ_ASSERT(state.initialized()); + + AutoLockHelperThreadState lock; + + if (!state.live().putNew(this)) { + ReportOutOfMemory(cx); + return false; + } + + registered_ = true; + return true; +} + +void OffThreadPromiseTask::unregister(OffThreadPromiseRuntimeState& state) { + MOZ_ASSERT(registered_); + AutoLockHelperThreadState lock; + state.live().remove(this); + registered_ = false; +} + +void OffThreadPromiseTask::run(JSContext* cx, + MaybeShuttingDown maybeShuttingDown) { + MOZ_ASSERT(cx->runtime() == runtime_); + MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_)); + MOZ_ASSERT(registered_); + + // Remove this task from live_ before calling `resolve`, so that if `resolve` + // itself drains the queue reentrantly, the queue will not think this task is + // yet to be queued and block waiting for it. + // + // The unregister method synchronizes on the helper thread lock and ensures + // that we don't delete the task while the helper thread is still running. + OffThreadPromiseRuntimeState& state = runtime_->offThreadPromiseState.ref(); + MOZ_ASSERT(state.initialized()); + unregister(state); + + if (maybeShuttingDown == JS::Dispatchable::NotShuttingDown) { + // We can't leave a pending exception when returning to the caller so do + // the same thing as Gecko, which is to ignore the error. This should + // only happen due to OOM or interruption. + AutoRealm ar(cx, promise_); + if (!resolve(cx, promise_)) { + cx->clearPendingException(); + } + } + + js_delete(this); +} + +void OffThreadPromiseTask::dispatchResolveAndDestroy() { + AutoLockHelperThreadState lock; + dispatchResolveAndDestroy(lock); +} + +void OffThreadPromiseTask::dispatchResolveAndDestroy( + const AutoLockHelperThreadState& lock) { + MOZ_ASSERT(registered_); + + OffThreadPromiseRuntimeState& state = runtime_->offThreadPromiseState.ref(); + MOZ_ASSERT(state.initialized()); + MOZ_ASSERT(state.live().has(this)); + + // If the dispatch succeeds, then we are guaranteed that run() will be + // called on an active JSContext of runtime_. + if (state.dispatchToEventLoopCallback_(state.dispatchToEventLoopClosure_, + this)) { + return; + } + + // The DispatchToEventLoopCallback has rejected this task, indicating that + // shutdown has begun. Count the number of rejected tasks that have called + // dispatchResolveAndDestroy, and when they account for the entire contents of + // live_, notify OffThreadPromiseRuntimeState::shutdown that it is safe to + // destruct them. + state.numCanceled_++; + if (state.numCanceled_ == state.live().count()) { + state.allCanceled().notify_one(); + } +} + +OffThreadPromiseRuntimeState::OffThreadPromiseRuntimeState() + : dispatchToEventLoopCallback_(nullptr), + dispatchToEventLoopClosure_(nullptr), + numCanceled_(0), + internalDispatchQueueClosed_(false) {} + +OffThreadPromiseRuntimeState::~OffThreadPromiseRuntimeState() { + MOZ_ASSERT(live_.refNoCheck().empty()); + MOZ_ASSERT(numCanceled_ == 0); + MOZ_ASSERT(internalDispatchQueue_.refNoCheck().empty()); + MOZ_ASSERT(!initialized()); +} + +void OffThreadPromiseRuntimeState::init( + JS::DispatchToEventLoopCallback callback, void* closure) { + MOZ_ASSERT(!initialized()); + + dispatchToEventLoopCallback_ = callback; + dispatchToEventLoopClosure_ = closure; + + MOZ_ASSERT(initialized()); +} + +/* static */ +bool OffThreadPromiseRuntimeState::internalDispatchToEventLoop( + void* closure, JS::Dispatchable* d) { + OffThreadPromiseRuntimeState& state = + *reinterpret_cast<OffThreadPromiseRuntimeState*>(closure); + MOZ_ASSERT(state.usingInternalDispatchQueue()); + gHelperThreadLock.assertOwnedByCurrentThread(); + + if (state.internalDispatchQueueClosed_) { + return false; + } + + // The JS API contract is that 'false' means shutdown, so be infallible + // here (like Gecko). + AutoEnterOOMUnsafeRegion noOOM; + if (!state.internalDispatchQueue().pushBack(d)) { + noOOM.crash("internalDispatchToEventLoop"); + } + + // Wake up internalDrain() if it is waiting for a job to finish. + state.internalDispatchQueueAppended().notify_one(); + return true; +} + +bool OffThreadPromiseRuntimeState::usingInternalDispatchQueue() const { + return dispatchToEventLoopCallback_ == internalDispatchToEventLoop; +} + +void OffThreadPromiseRuntimeState::initInternalDispatchQueue() { + init(internalDispatchToEventLoop, this); + MOZ_ASSERT(usingInternalDispatchQueue()); +} + +bool OffThreadPromiseRuntimeState::initialized() const { + return !!dispatchToEventLoopCallback_; +} + +void OffThreadPromiseRuntimeState::internalDrain(JSContext* cx) { + MOZ_ASSERT(usingInternalDispatchQueue()); + + for (;;) { + JS::Dispatchable* d; + { + AutoLockHelperThreadState lock; + + MOZ_ASSERT(!internalDispatchQueueClosed_); + MOZ_ASSERT_IF(!internalDispatchQueue().empty(), !live().empty()); + if (live().empty()) { + return; + } + + // There are extant live OffThreadPromiseTasks. If none are in the queue, + // block until one of them finishes and enqueues a dispatchable. + while (internalDispatchQueue().empty()) { + internalDispatchQueueAppended().wait(lock); + } + + d = internalDispatchQueue().popCopyFront(); + } + + // Don't call run() with lock held to avoid deadlock. + d->run(cx, JS::Dispatchable::NotShuttingDown); + } +} + +bool OffThreadPromiseRuntimeState::internalHasPending() { + MOZ_ASSERT(usingInternalDispatchQueue()); + + AutoLockHelperThreadState lock; + MOZ_ASSERT(!internalDispatchQueueClosed_); + MOZ_ASSERT_IF(!internalDispatchQueue().empty(), !live().empty()); + return !live().empty(); +} + +void OffThreadPromiseRuntimeState::shutdown(JSContext* cx) { + if (!initialized()) { + return; + } + + AutoLockHelperThreadState lock; + + // When the shell is using the internal event loop, we must simulate our + // requirement of the embedding that, before shutdown, all successfully- + // dispatched-to-event-loop tasks have been run. + if (usingInternalDispatchQueue()) { + DispatchableFifo dispatchQueue; + { + std::swap(dispatchQueue, internalDispatchQueue()); + MOZ_ASSERT(internalDispatchQueue().empty()); + internalDispatchQueueClosed_ = true; + } + + // Don't call run() with lock held to avoid deadlock. + AutoUnlockHelperThreadState unlock(lock); + for (JS::Dispatchable* d : dispatchQueue) { + d->run(cx, JS::Dispatchable::ShuttingDown); + } + } + + // An OffThreadPromiseTask may only be safely deleted on its JSContext's + // thread (since it contains a PersistentRooted holding its promise), and + // only after it has called dispatchResolveAndDestroy (since that is our + // only indication that its owner is done writing into it). + // + // OffThreadPromiseTasks accepted by the DispatchToEventLoopCallback are + // deleted by their 'run' methods. Only dispatchResolveAndDestroy invokes + // the callback, and the point of the callback is to call 'run' on the + // JSContext's thread, so the conditions above are met. + // + // But although the embedding's DispatchToEventLoopCallback promises to run + // every task it accepts before shutdown, when shutdown does begin it starts + // rejecting tasks; we cannot count on 'run' to clean those up for us. + // Instead, dispatchResolveAndDestroy keeps a count of rejected ('canceled') + // tasks; once that count covers everything in live_, this function itself + // runs only on the JSContext's thread, so we can delete them all here. + while (live().count() != numCanceled_) { + MOZ_ASSERT(numCanceled_ < live().count()); + allCanceled().wait(lock); + } + + // Now that live_ contains only cancelled tasks, we can just delete + // everything. + for (OffThreadPromiseTaskSet::Range r = live().all(); !r.empty(); + r.popFront()) { + OffThreadPromiseTask* task = r.front(); + + // We don't want 'task' to unregister itself (which would mutate live_ while + // we are iterating over it) so reset its internal registered_ flag. + MOZ_ASSERT(task->registered_); + task->registered_ = false; + js_delete(task); + } + live().clear(); + numCanceled_ = 0; + + // After shutdown, there should be no OffThreadPromiseTask activity in this + // JSRuntime. Revert to the !initialized() state to catch bugs. + dispatchToEventLoopCallback_ = nullptr; + MOZ_ASSERT(!initialized()); +} |