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1 // Copyright 2014 The Chromium Authors. All rights reserved. | 1 // Copyright 2014 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "base/memory/discardable_shared_memory.h" | 5 #include "base/memory/discardable_shared_memory.h" |
6 | 6 |
7 #if defined(OS_POSIX) | 7 #if defined(OS_POSIX) |
8 #include <unistd.h> | 8 #include <unistd.h> |
9 #endif | 9 #endif |
10 | 10 |
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150 | 150 |
151 locked_page_count_ = AlignToPageSize(mapped_size_) / base::GetPageSize(); | 151 locked_page_count_ = AlignToPageSize(mapped_size_) / base::GetPageSize(); |
152 #if DCHECK_IS_ON() | 152 #if DCHECK_IS_ON() |
153 for (size_t page = 0; page < locked_page_count_; ++page) | 153 for (size_t page = 0; page < locked_page_count_; ++page) |
154 locked_pages_.insert(page); | 154 locked_pages_.insert(page); |
155 #endif | 155 #endif |
156 | 156 |
157 return true; | 157 return true; |
158 } | 158 } |
159 | 159 |
160 bool DiscardableSharedMemory::Lock(size_t offset, size_t length) { | 160 DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock( |
| 161 size_t offset, size_t length) { |
161 DCHECK_EQ(AlignToPageSize(offset), offset); | 162 DCHECK_EQ(AlignToPageSize(offset), offset); |
162 DCHECK_EQ(AlignToPageSize(length), length); | 163 DCHECK_EQ(AlignToPageSize(length), length); |
163 | 164 |
164 // Calls to this function must synchronized properly. | 165 // Calls to this function must synchronized properly. |
165 DFAKE_SCOPED_LOCK(thread_collision_warner_); | 166 DFAKE_SCOPED_LOCK(thread_collision_warner_); |
166 | 167 |
167 // Return false when instance has been purged or not initialized properly by | 168 // Return false when instance has been purged or not initialized properly by |
168 // checking if |last_known_usage_| is NULL. | 169 // checking if |last_known_usage_| is NULL. |
169 if (last_known_usage_.is_null()) | 170 if (last_known_usage_.is_null()) |
170 return false; | 171 return FAILED; |
171 | 172 |
172 DCHECK(shared_memory_.memory()); | 173 DCHECK(shared_memory_.memory()); |
173 | 174 |
174 // We need to successfully acquire the platform independent lock before | 175 // We need to successfully acquire the platform independent lock before |
175 // individual pages can be locked. | 176 // individual pages can be locked. |
176 if (!locked_page_count_) { | 177 if (!locked_page_count_) { |
177 SharedState old_state(SharedState::UNLOCKED, last_known_usage_); | 178 SharedState old_state(SharedState::UNLOCKED, last_known_usage_); |
178 SharedState new_state(SharedState::LOCKED, Time()); | 179 SharedState new_state(SharedState::LOCKED, Time()); |
179 SharedState result(subtle::Acquire_CompareAndSwap( | 180 SharedState result(subtle::Acquire_CompareAndSwap( |
180 &SharedStateFromSharedMemory(shared_memory_)->value.i, | 181 &SharedStateFromSharedMemory(shared_memory_)->value.i, |
181 old_state.value.i, | 182 old_state.value.i, |
182 new_state.value.i)); | 183 new_state.value.i)); |
183 if (result.value.u != old_state.value.u) { | 184 if (result.value.u != old_state.value.u) { |
184 // Update |last_known_usage_| in case the above CAS failed because of | 185 // Update |last_known_usage_| in case the above CAS failed because of |
185 // an incorrect timestamp. | 186 // an incorrect timestamp. |
186 last_known_usage_ = result.GetTimestamp(); | 187 last_known_usage_ = result.GetTimestamp(); |
187 return false; | 188 return FAILED; |
188 } | 189 } |
189 } | 190 } |
190 | 191 |
191 // Zero for length means "everything onward". | 192 // Zero for length means "everything onward". |
192 if (!length) | 193 if (!length) |
193 length = AlignToPageSize(mapped_size_) - offset; | 194 length = AlignToPageSize(mapped_size_) - offset; |
194 | 195 |
195 size_t start = offset / base::GetPageSize(); | 196 size_t start = offset / base::GetPageSize(); |
196 size_t end = start + length / base::GetPageSize(); | 197 size_t end = start + length / base::GetPageSize(); |
197 DCHECK_LT(start, end); | 198 DCHECK_LT(start, end); |
198 DCHECK_LE(end, AlignToPageSize(mapped_size_) / base::GetPageSize()); | 199 DCHECK_LE(end, AlignToPageSize(mapped_size_) / base::GetPageSize()); |
199 | 200 |
200 // Add pages to |locked_page_count_|. | 201 // Add pages to |locked_page_count_|. |
201 // Note: Locking a page that is already locked is an error. | 202 // Note: Locking a page that is already locked is an error. |
202 locked_page_count_ += end - start; | 203 locked_page_count_ += end - start; |
203 #if DCHECK_IS_ON() | 204 #if DCHECK_IS_ON() |
204 // Detect incorrect usage by keeping track of exactly what pages are locked. | 205 // Detect incorrect usage by keeping track of exactly what pages are locked. |
205 for (auto page = start; page < end; ++page) { | 206 for (auto page = start; page < end; ++page) { |
206 auto result = locked_pages_.insert(page); | 207 auto result = locked_pages_.insert(page); |
207 DCHECK(result.second); | 208 DCHECK(result.second); |
208 } | 209 } |
209 DCHECK_EQ(locked_pages_.size(), locked_page_count_); | 210 DCHECK_EQ(locked_pages_.size(), locked_page_count_); |
210 #endif | 211 #endif |
211 | 212 |
212 #if defined(OS_ANDROID) | 213 #if defined(OS_ANDROID) |
213 SharedMemoryHandle handle = shared_memory_.handle(); | 214 SharedMemoryHandle handle = shared_memory_.handle(); |
214 DCHECK(SharedMemory::IsHandleValid(handle)); | 215 DCHECK(SharedMemory::IsHandleValid(handle)); |
215 if (ashmem_pin_region( | 216 if (ashmem_pin_region( |
216 handle.fd, AlignToPageSize(sizeof(SharedState)) + offset, length)) { | 217 handle.fd, AlignToPageSize(sizeof(SharedState)) + offset, length)) { |
217 return false; | 218 return PURGED; |
218 } | 219 } |
219 #endif | 220 #endif |
220 | 221 |
221 return true; | 222 return SUCCESS; |
222 } | 223 } |
223 | 224 |
224 void DiscardableSharedMemory::Unlock(size_t offset, size_t length) { | 225 void DiscardableSharedMemory::Unlock(size_t offset, size_t length) { |
225 DCHECK_EQ(AlignToPageSize(offset), offset); | 226 DCHECK_EQ(AlignToPageSize(offset), offset); |
226 DCHECK_EQ(AlignToPageSize(length), length); | 227 DCHECK_EQ(AlignToPageSize(length), length); |
227 | 228 |
228 // Calls to this function must synchronized properly. | 229 // Calls to this function must synchronized properly. |
229 DFAKE_SCOPED_LOCK(thread_collision_warner_); | 230 DFAKE_SCOPED_LOCK(thread_collision_warner_); |
230 | 231 |
231 // Zero for length means "everything onward". | 232 // Zero for length means "everything onward". |
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354 shared_memory_.Unmap(); | 355 shared_memory_.Unmap(); |
355 shared_memory_.Close(); | 356 shared_memory_.Close(); |
356 mapped_size_ = 0; | 357 mapped_size_ = 0; |
357 } | 358 } |
358 | 359 |
359 Time DiscardableSharedMemory::Now() const { | 360 Time DiscardableSharedMemory::Now() const { |
360 return Time::Now(); | 361 return Time::Now(); |
361 } | 362 } |
362 | 363 |
363 } // namespace base | 364 } // namespace base |
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