| #pragma once |
| |
| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| // Signaling mechanism that allows threads to signal changes to shared |
| // memory and to wait for signals. |
| |
| namespace vsoc { |
| /** |
| * Defines the strategy for signaling among threads on a single kernel. |
| */ |
| namespace SingleSidedSignal { |
| /** |
| * Waits for a signal, assuming the the word at addr matches expected_state. |
| * Will return immediately if the value does not match. |
| * Callers must be equipped to cope with spurious returns. |
| */ |
| static void AwaitSignal(uint32_t expected_state, uint32_t* uaddr) { |
| syscall(SYS_futex, uaddr, FUTEX_WAIT, expected_state, nullptr, nullptr, 0); |
| } |
| |
| /** |
| * Sends a signal to every thread in AwaitSignal() using the address in |
| * uaddr. |
| */ |
| static void Signal(std::atomic<uint32_t>* uaddr) { |
| syscall(SYS_futex, reinterpret_cast<int32_t*>(uaddr), FUTEX_WAKE, -1, nullptr, |
| nullptr, 0); |
| } |
| } // namespace SingleSidedSignal |
| } // namespace vsoc |
