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 #include "src/core/lib/event_engine/posix_engine/posix_engine_closure.h" 24 25 namespace grpc_event_engine { 26 namespace experimental { 27 28 class Scheduler; 29 30 class LockfreeEvent { 31 public: LockfreeEvent(Scheduler * scheduler)32 explicit LockfreeEvent(Scheduler* scheduler) : scheduler_(scheduler) {} 33 34 LockfreeEvent(const LockfreeEvent&) = delete; 35 LockfreeEvent& operator=(const LockfreeEvent&) = delete; 36 37 // These methods are used to initialize and destroy the internal state. These 38 // cannot be done in constructor and destructor because SetReady may be called 39 // when the event is destroyed and put in a freelist. 40 void InitEvent(); 41 void DestroyEvent(); 42 43 // Returns true if fd has been shutdown, false otherwise. IsShutdown()44 bool IsShutdown() const { 45 return (state_.load(std::memory_order_relaxed) & kShutdownBit) != 0; 46 } 47 48 // Schedules \a closure when the event is received (see SetReady()) or the 49 // shutdown state has been set. Note that the event may have already been 50 // received, in which case the closure would be scheduled immediately. 51 // If the shutdown state has already been set, then \a closure is scheduled 52 // with the shutdown error. 53 void NotifyOn(PosixEngineClosure* closure); 54 55 // Sets the shutdown state. If a closure had been provided by NotifyOn and has 56 // not yet been scheduled, it will be scheduled with \a shutdown_error. 57 bool SetShutdown(absl::Status shutdown_error); 58 59 // Signals that the event has been received. 60 void SetReady(); 61 62 private: 63 enum State { kClosureNotReady = 0, kClosureReady = 2, kShutdownBit = 1 }; 64 65 std::atomic<intptr_t> state_; 66 Scheduler* scheduler_; 67 }; 68 69 } // namespace experimental 70 } // namespace grpc_event_engine 71 72 #endif // GRPC_SRC_CORE_LIB_EVENT_ENGINE_POSIX_ENGINE_LOCKFREE_EVENT_H 73