1 // Copyright 2022 The gRPC Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef GRPC_SRC_CORE_LIB_EVENT_ENGINE_POSIX_ENGINE_LOCKFREE_EVENT_H 16 #define GRPC_SRC_CORE_LIB_EVENT_ENGINE_POSIX_ENGINE_LOCKFREE_EVENT_H 17 #include <grpc/support/port_platform.h> 18 19 #include <atomic> 20 #include <cstdint> 21 22 #include "absl/status/status.h" 23 24 #include "src/core/lib/event_engine/posix_engine/posix_engine_closure.h" 25 26 namespace grpc_event_engine { 27 namespace experimental { 28 29 class Scheduler; 30 31 class LockfreeEvent { 32 public: LockfreeEvent(Scheduler * scheduler)33 explicit LockfreeEvent(Scheduler* scheduler) : scheduler_(scheduler) {} 34 35 LockfreeEvent(const LockfreeEvent&) = delete; 36 LockfreeEvent& operator=(const LockfreeEvent&) = delete; 37 38 // These methods are used to initialize and destroy the internal state. These 39 // cannot be done in constructor and destructor because SetReady may be called 40 // when the event is destroyed and put in a freelist. 41 void InitEvent(); 42 void DestroyEvent(); 43 44 // Returns true if fd has been shutdown, false otherwise. IsShutdown()45 bool IsShutdown() const { 46 return (state_.load(std::memory_order_relaxed) & kShutdownBit) != 0; 47 } 48 49 // Schedules \a closure when the event is received (see SetReady()) or the 50 // shutdown state has been set. Note that the event may have already been 51 // received, in which case the closure would be scheduled immediately. 52 // If the shutdown state has already been set, then \a closure is scheduled 53 // with the shutdown error. 54 void NotifyOn(PosixEngineClosure* closure); 55 56 // Sets the shutdown state. If a closure had been provided by NotifyOn and has 57 // not yet been scheduled, it will be scheduled with \a shutdown_error. 58 bool SetShutdown(absl::Status shutdown_error); 59 60 // Signals that the event has been received. 61 void SetReady(); 62 63 private: 64 enum State { kClosureNotReady = 0, kClosureReady = 2, kShutdownBit = 1 }; 65 66 std::atomic<intptr_t> state_; 67 Scheduler* scheduler_; 68 }; 69 70 } // namespace experimental 71 } // namespace grpc_event_engine 72 73 #endif // GRPC_SRC_CORE_LIB_EVENT_ENGINE_POSIX_ENGINE_LOCKFREE_EVENT_H 74