e3cbb3d4a9
This patch introduces ClientDirectoryLockHandle, a new RAII-style wrapper around ClientDirectoryLock. The handle ensures that the directory lock remains acquired for the lifetime of the handle, and that appropriate cleanup occurs automatically when the handle is destroyed. It is move-only and provides convenient access to the underlying ClientDirectoryLock via operator overloads and a getter. It also supports thread assertions through AssertIsOnOwningThread. Currently, clients hold a RefPtr<ClientDirectoryLock> and must manually drop the lock before nulling the RefPtr. This class is intended to make that process safer and easier to follow. OpenClientDirectory will be updated in a follow-up patch to return ClientDirectoryLockHandle. Differential Revision: https://phabricator.services.mozilla.com/D243654
117 lines
3.7 KiB
C++
117 lines
3.7 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 file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/dom/quota/ClientDirectoryLockHandle.h"
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#include "mozilla/dom/quota/ClientDirectoryLock.h"
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#include "mozilla/dom/quota/DirectoryLock.h"
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#include "mozilla/dom/quota/DirectoryLockInlines.h"
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namespace mozilla::dom::quota {
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ClientDirectoryLockHandle::ClientDirectoryLockHandle() {
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MOZ_COUNT_CTOR(mozilla::dom::quota::ClientDirectoryLockHandle);
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}
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ClientDirectoryLockHandle::ClientDirectoryLockHandle(
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RefPtr<ClientDirectoryLock> aClientDirectoryLock) {
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aClientDirectoryLock->AssertIsOnOwningThread();
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mClientDirectoryLock = std::move(aClientDirectoryLock);
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MOZ_COUNT_CTOR(mozilla::dom::quota::ClientDirectoryLockHandle);
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}
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ClientDirectoryLockHandle::ClientDirectoryLockHandle(
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ClientDirectoryLockHandle&& aOther) noexcept {
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aOther.AssertIsOnOwningThread();
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mClientDirectoryLock = std::move(aOther.mClientDirectoryLock);
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// Explicitly null aOther.mClientDirectoryLock so that aOther appears inert
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// immediately after the move. While RefPtr nulls out its mRawPtr internally,
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// the store may be reordered in optimized builds, possibly occurring only
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// just before RefPtr’s own destructor runs. Without this, the moved-from
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// handle’s destructor may observe a stale non-null value.
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aOther.mClientDirectoryLock = nullptr;
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MOZ_COUNT_CTOR(mozilla::dom::quota::ClientDirectoryLockHandle);
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}
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ClientDirectoryLockHandle::~ClientDirectoryLockHandle() {
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// If mClientDirectoryLock is null, this handle is in an inert state — either
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// it was default-constructed or moved.
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//
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// This check is safe here because destruction implies no other thread is
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// using the handle. Any use-after-destroy bugs would indicate a much more
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// serious issue (e.g., a dangling pointer), and should be caught by tools
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// like AddressSanitizer.
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if (mClientDirectoryLock) {
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AssertIsOnOwningThread();
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DropDirectoryLock(mClientDirectoryLock);
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}
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MOZ_COUNT_DTOR(mozilla::dom::quota::ClientDirectoryLockHandle);
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}
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void ClientDirectoryLockHandle::AssertIsOnOwningThread() const {
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NS_ASSERT_OWNINGTHREAD(ClientDirectoryLockHandle);
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}
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ClientDirectoryLockHandle& ClientDirectoryLockHandle::operator=(
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ClientDirectoryLockHandle&& aOther) noexcept {
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AssertIsOnOwningThread();
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aOther.AssertIsOnOwningThread();
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if (this != &aOther) {
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mClientDirectoryLock = std::move(aOther.mClientDirectoryLock);
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// Explicitly null aOther.mClientDirectoryLock so that aOther appears inert
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// immediately after the move. While RefPtr nulls out its mRawPtr
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// internally, the store may be reordered in optimized builds, possibly
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// occurring only just before RefPtr’s own destructor runs. Without this,
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// the moved-from handle’s destructor may observe a stale non-null value.
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aOther.mClientDirectoryLock = nullptr;
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}
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return *this;
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}
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ClientDirectoryLockHandle::operator bool() const {
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AssertIsOnOwningThread();
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return !!mClientDirectoryLock;
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}
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ClientDirectoryLock* ClientDirectoryLockHandle::get() const {
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AssertIsOnOwningThread();
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return mClientDirectoryLock ? mClientDirectoryLock.get() : nullptr;
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}
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ClientDirectoryLock& ClientDirectoryLockHandle::operator*() const {
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AssertIsOnOwningThread();
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return *get();
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}
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ClientDirectoryLock* ClientDirectoryLockHandle::operator->() const {
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AssertIsOnOwningThread();
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return get();
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}
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#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
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bool ClientDirectoryLockHandle::IsInert() const {
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return !mClientDirectoryLock;
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}
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#endif
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} // namespace mozilla::dom::quota
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