forked from mirrors/gecko-dev
b3df452cb8
We had `NS_DispatchMemoryPressure` and `NS_DispatchEventualMemoryPressure` to dispatch a memory-pressure event which took `MemPressure_New` and `MemPressure_Ongoing` to translate into "low-memory" and "low-memory-ongoing" message respectively. With that model, we could end up sending a wrong message if somebody called the API with `MemPressure_Ongoing` without sending `MemPressure_New`. To avoid that, this patch removes `MemPressure_Ongoing` and makes the API decide whether it should dispatch a "new" event or "ongoing" event. Differential Revision: https://phabricator.services.mozilla.com/D119122
102 lines
3.5 KiB
C++
102 lines
3.5 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsMemoryPressure.h"
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#include "mozilla/Assertions.h"
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#include "mozilla/Atomics.h"
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#include "nsThreadUtils.h"
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using namespace mozilla;
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const char* const kTopicMemoryPressure = "memory-pressure";
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const char* const kTopicMemoryPressureStop = "memory-pressure-stop";
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const char16_t* const kSubTopicLowMemoryNew = u"low-memory";
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const char16_t* const kSubTopicLowMemoryOngoing = u"low-memory-ongoing";
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// This is accessed from any thread through NS_NotifyOfEventualMemoryPressure
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static Atomic<MemoryPressureState, Relaxed> sMemoryPressurePending(
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MemoryPressureState::NoPressure);
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void NS_NotifyOfEventualMemoryPressure(MemoryPressureState aState) {
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MOZ_ASSERT(aState != MemoryPressureState::None);
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/*
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* A new memory pressure event erases an ongoing (or stop of) memory pressure,
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* but an existing "new" memory pressure event takes precedence over a new
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* "ongoing" or "stop" memory pressure event.
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*/
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switch (aState) {
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case MemoryPressureState::None:
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case MemoryPressureState::LowMemory:
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sMemoryPressurePending = aState;
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break;
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case MemoryPressureState::NoPressure:
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sMemoryPressurePending.compareExchange(MemoryPressureState::None, aState);
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break;
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}
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}
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nsresult NS_NotifyOfMemoryPressure(MemoryPressureState aState) {
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NS_NotifyOfEventualMemoryPressure(aState);
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nsCOMPtr<nsIRunnable> event =
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new Runnable("NS_DispatchEventualMemoryPressure");
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return NS_DispatchToMainThread(event);
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}
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void NS_DispatchMemoryPressure() {
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MOZ_ASSERT(NS_IsMainThread());
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static MemoryPressureState sMemoryPressureStatus =
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MemoryPressureState::NoPressure;
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MemoryPressureState mpPending =
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sMemoryPressurePending.exchange(MemoryPressureState::None);
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if (mpPending == MemoryPressureState::None) {
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return;
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}
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nsCOMPtr<nsIObserverService> os = services::GetObserverService();
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if (!os) {
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NS_WARNING("Can't get observer service!");
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return;
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}
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switch (mpPending) {
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case MemoryPressureState::None:
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MOZ_ASSERT_UNREACHABLE("Already handled this case above.");
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break;
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case MemoryPressureState::LowMemory:
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switch (sMemoryPressureStatus) {
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case MemoryPressureState::None:
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MOZ_ASSERT_UNREACHABLE("The internal status should never be None.");
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break;
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case MemoryPressureState::NoPressure:
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sMemoryPressureStatus = MemoryPressureState::LowMemory;
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os->NotifyObservers(nullptr, kTopicMemoryPressure,
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kSubTopicLowMemoryNew);
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break;
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case MemoryPressureState::LowMemory:
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os->NotifyObservers(nullptr, kTopicMemoryPressure,
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kSubTopicLowMemoryOngoing);
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break;
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}
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break;
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case MemoryPressureState::NoPressure:
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switch (sMemoryPressureStatus) {
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case MemoryPressureState::None:
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MOZ_ASSERT_UNREACHABLE("The internal status should never be None.");
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break;
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case MemoryPressureState::NoPressure:
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// Already no pressure. Do nothing.
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break;
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case MemoryPressureState::LowMemory:
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sMemoryPressureStatus = MemoryPressureState::NoPressure;
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os->NotifyObservers(nullptr, kTopicMemoryPressureStop, nullptr);
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break;
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}
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break;
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}
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}
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