2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 /* override-include-guard */
19 #error "This should only be included by hazptr.h"
22 #include <folly/experimental/hazptr/debug.h>
24 #include <unordered_set>
31 constexpr hazptr_domain::hazptr_domain(memory_resource* mr) noexcept
34 /** hazptr_obj_base */
36 template <typename T, typename D>
37 inline void hazptr_obj_base<T, D>::retire(hazptr_domain& domain, D deleter) {
38 DEBUG_PRINT(this << " " << &domain);
39 deleter_ = std::move(deleter);
40 reclaim_ = [](hazptr_obj* p) {
41 auto hobp = static_cast<hazptr_obj_base*>(p);
42 auto obj = static_cast<T*>(hobp);
45 domain.objRetire(this);
51 friend class hazptr_domain;
52 template <typename> friend class hazptr_owner;
54 std::atomic<const void*> hazptr_ = {nullptr};
55 hazptr_rec* next_ = {nullptr};
56 std::atomic<bool> active_ = {false};
58 void set(const void* p) noexcept;
59 const void* get() const noexcept;
60 void clear() noexcept;
61 void release() noexcept;
67 inline hazptr_owner<T>::hazptr_owner(hazptr_domain& domain) {
69 hazptr_ = domain_->hazptrAcquire();
70 DEBUG_PRINT(this << " " << domain_ << " " << hazptr_);
71 if (hazptr_ == nullptr) { std::bad_alloc e; throw e; }
75 hazptr_owner<T>::~hazptr_owner() {
77 domain_->hazptrRelease(hazptr_);
81 inline bool hazptr_owner<T>::try_protect(
83 const std::atomic<T*>& src) noexcept {
84 DEBUG_PRINT(this << " " << ptr << " " << &src);
96 inline T* hazptr_owner<T>::get_protected(const std::atomic<T*>& src) noexcept {
98 while (!try_protect(p, src)) {}
99 DEBUG_PRINT(this << " " << p << " " << &src);
103 template <typename T>
104 inline void hazptr_owner<T>::set(const T* ptr) noexcept {
105 DEBUG_PRINT(this << " " << ptr);
109 template <typename T>
110 inline void hazptr_owner<T>::clear() noexcept {
115 template <typename T>
116 inline void hazptr_owner<T>::swap(hazptr_owner<T>& rhs) noexcept {
118 this << " " << this->hazptr_ << " " << this->domain_ << " -- "
119 << &rhs << " " << rhs.hazptr_ << " " << rhs.domain_);
120 std::swap(this->domain_, rhs.domain_);
121 std::swap(this->hazptr_, rhs.hazptr_);
124 template <typename T>
125 inline void swap(hazptr_owner<T>& lhs, hazptr_owner<T>& rhs) noexcept {
129 ////////////////////////////////////////////////////////////////////////////////
130 // Non-template part of implementation
131 ////////////////////////////////////////////////////////////////////////////////
133 // - Thread caching of hazptr_rec-s
134 // - Private storage of retired objects
135 // - Control of reclamation (when and by whom)
136 // - Optimized memory order
138 /** Definition of default_hazptr_domain() */
139 inline hazptr_domain& default_hazptr_domain() {
140 static hazptr_domain d;
147 inline void hazptr_rec::set(const void* p) noexcept {
148 DEBUG_PRINT(this << " " << p);
152 inline const void* hazptr_rec::get() const noexcept {
153 DEBUG_PRINT(this << " " << hazptr_.load());
154 return hazptr_.load();
157 inline void hazptr_rec::clear() noexcept {
159 hazptr_.store(nullptr);
162 inline void hazptr_rec::release() noexcept {
165 active_.store(false);
170 inline const void* hazptr_obj::getObjPtr() const {
177 inline hazptr_domain::~hazptr_domain() {
179 { /* free all hazptr_rec-s */
181 for (auto p = hazptrs_.load(); p; p = next) {
183 mr_->deallocate(static_cast<void*>(p), sizeof(hazptr_rec));
186 { /* reclaim all remaining retired objects */
188 for (auto p = retired_.load(); p; p = next) {
195 inline void hazptr_domain::try_reclaim() {
201 inline hazptr_rec* hazptr_domain::hazptrAcquire() {
204 for (p = hazptrs_.load(); p; p = next) {
206 bool active = p->active_.load();
208 if (p->active_.compare_exchange_weak(active, true)) {
209 DEBUG_PRINT(this << " " << p);
214 p = static_cast<hazptr_rec*>(mr_->allocate(sizeof(hazptr_rec)));
218 p->active_.store(true);
220 p->next_ = hazptrs_.load();
221 if (hazptrs_.compare_exchange_weak(p->next_, p)) {
225 auto hcount = hcount_.fetch_add(1);
226 DEBUG_PRINT(this << " " << p << " " << sizeof(hazptr_rec) << " " << hcount);
230 inline void hazptr_domain::hazptrRelease(hazptr_rec* p) noexcept {
231 DEBUG_PRINT(this << " " << p);
236 hazptr_domain::pushRetired(hazptr_obj* head, hazptr_obj* tail, int count) {
237 tail->next_ = retired_.load();
238 while (!retired_.compare_exchange_weak(tail->next_, head)) {}
239 return rcount_.fetch_add(count);
242 inline void hazptr_domain::objRetire(hazptr_obj* p) {
243 auto rcount = pushRetired(p, p, 1) + 1;
244 if (rcount >= kScanThreshold * hcount_.load()) {
249 inline void hazptr_domain::tryBulkReclaim() {
252 auto hcount = hcount_.load();
253 auto rcount = rcount_.load();
254 if (rcount < kScanThreshold * hcount) {
257 if (rcount_.compare_exchange_weak(rcount, 0)) {
264 inline void hazptr_domain::bulkReclaim() {
266 auto p = retired_.exchange(nullptr);
267 auto h = hazptrs_.load();
268 std::unordered_set<const void*> hs;
269 for (; h; h = h->next_) {
270 hs.insert(h->hazptr_.load());
273 hazptr_obj* retired = nullptr;
274 hazptr_obj* tail = nullptr;
276 for (; p; p = next) {
278 if (hs.count(p->getObjPtr()) == 0) {
279 DEBUG_PRINT(this << " " << p << " " << p->reclaim_);
284 if (tail == nullptr) {
291 pushRetired(retired, tail, rcount);
296 } // namespace hazptr