event_loop.h revision 341292509cfde0f859d89bda4ca5d55fc9772e64
1/* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 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 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 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. 15 */ 16 17#ifndef CHRE_CORE_EVENT_LOOP_H_ 18#define CHRE_CORE_EVENT_LOOP_H_ 19 20#include "chre/core/event.h" 21#include "chre/core/nanoapp.h" 22#include "chre/core/timer_pool.h" 23#include "chre/platform/mutex.h" 24#include "chre/platform/platform_nanoapp.h" 25#include "chre/util/dynamic_vector.h" 26#include "chre/util/fixed_size_blocking_queue.h" 27#include "chre/util/non_copyable.h" 28#include "chre/util/synchronized_memory_pool.h" 29#include "chre/util/unique_ptr.h" 30 31namespace chre { 32 33/** 34 * The EventLoop represents a single thread of execution that is shared among 35 * zero or more nanoapps. As the name implies, the EventLoop is built around a 36 * loop that delivers events to the nanoapps managed within for processing. 37 */ 38class EventLoop : public NonCopyable { 39 public: 40 /** 41 * Setup the event loop. 42 */ 43 EventLoop(); 44 45 /** 46 * Synchronous callback used with forEachNanoapp 47 */ 48 typedef void (NanoappCallbackFunction)(const Nanoapp *nanoapp, void *data); 49 50 /** 51 * Searches the set of nanoapps managed by this EventLoop for one with the 52 * given app ID. If found, provides its instance ID, which can be used to send 53 * events to the app. 54 * 55 * This function is safe to call from any thread. 56 * 57 * @param appId The nanoapp identifier to search for. 58 * @param instanceId If this function returns true, will be populated with the 59 * instanceId associated with the given appId; otherwise unmodified. 60 * Must not be null. 61 * @return true if the given app ID was found and instanceId was populated 62 */ 63 bool findNanoappInstanceIdByAppId(uint64_t appId, uint32_t *instanceId); 64 65 /** 66 * Iterates over the list of Nanoapps managed by this EventLoop, and invokes 67 * the supplied callback for each one. This holds a lock if necessary, so it 68 * is safe to call from any thread. 69 * 70 * @param callback Function to invoke on each Nanoapp (synchronously) 71 * @param data Arbitrary data to pass to the callback 72 */ 73 void forEachNanoapp(NanoappCallbackFunction *callback, void *data); 74 75 /** 76 * Starts a nanoapp by constructing a Nanoapp instance, invoking the start 77 * entry point and adding it to the list of nanoapps owned by this event 78 * loop. 79 * 80 * @param platformNanoapp A pointer to the platform nanoapp to start. This 81 * pointer must remain valid after this function returns. 82 * @return True if the app was started successfully. 83 */ 84 bool startNanoapp(PlatformNanoapp *platformNanoapp); 85 86 /** 87 * Stops a nanoapp by invoking the stop entry point. The nanoapp passed in 88 * must have been previously started by the startNanoapp method. 89 * 90 * @param A pointer to the nanoapp to stop. 91 */ 92 void stopNanoapp(Nanoapp *nanoapp); 93 94 /** 95 * Executes the loop that blocks on the event queue and delivers received 96 * events to nanoapps. Only returns after stop() is called (from another 97 * context). 98 */ 99 void run(); 100 101 /** 102 * Signals the event loop currently executing in run() to exit gracefully at 103 * the next available opportunity. This function is thread-safe. 104 */ 105 void stop(); 106 107 /** 108 * Posts an event to a nanoapp that is currently running (or all nanoapps if 109 * the target instance ID is kBroadcastInstanceId). 110 * 111 * This function is safe to call from any thread. 112 * 113 * @param The type of data being posted. 114 * @param The data being posted. 115 * @param The callback to invoke when the event is no longer needed. 116 * @param The instance ID of the sender of this event. 117 * @param The instance ID of the destination of this event. 118 * 119 * @return true if the event was successfully added to the queue 120 */ 121 bool postEvent(uint16_t eventType, void *eventData, 122 chreEventCompleteFunction *freeCallback, 123 uint32_t senderInstanceId = kSystemInstanceId, 124 uint32_t targetInstanceId = kBroadcastInstanceId); 125 126 /** 127 * Returns a pointer to the currently executing Nanoapp, or nullptr if none is 128 * currently executing. Must only be called from within the thread context 129 * associated with this EventLoop. 130 * 131 * @return the currently executing nanoapp, or nullptr 132 */ 133 Nanoapp *getCurrentNanoapp() const; 134 135 /** 136 * Gets the number of nanoapps currently associated with this event loop. Must 137 * only be called within the context of this EventLoop. 138 * 139 * @return The number of nanoapps managed by this event loop 140 */ 141 size_t getNanoappCount() const; 142 143 /** 144 * Obtains the TimerPool associated with this event loop. 145 * 146 * @return The timer pool owned by this event loop. 147 */ 148 TimerPool& getTimerPool(); 149 150 /** 151 * Searches the set of nanoapps managed by this EventLoop for one with the 152 * given instance ID. 153 * 154 * This function is safe to call from any thread. 155 * 156 * @param instanceId The nanoapp instance ID to search for. 157 * @return a pointer to the found nanoapp or nullptr if no match was found. 158 */ 159 Nanoapp *findNanoappByInstanceId(uint32_t instanceId); 160 161 private: 162 //! The maximum number of events that can be active in the system. 163 static constexpr size_t kMaxEventCount = 1024; 164 165 //! The maximum number of events that are awaiting to be scheduled. These 166 //! events are in a queue to be distributed to apps. 167 static constexpr size_t kMaxUnscheduledEventCount = 1024; 168 169 //! The memory pool to allocate incoming events from. 170 SynchronizedMemoryPool<Event, kMaxEventCount> mEventPool; 171 172 //! The timer used schedule timed events for tasks running in this event loop. 173 TimerPool mTimerPool; 174 175 //! The list of nanoapps managed by this event loop. 176 DynamicVector<UniquePtr<Nanoapp>> mNanoapps; 177 178 //! This lock *must* be held whenever we: 179 //! (1) make changes to the mNanoapps vector, or 180 //! (2) read the mNanoapps vector from a thread other than the one 181 //! associated with this EventLoop 182 //! It is not necessary to acquire the lock when reading mNanoapps from within 183 //! the thread context of this EventLoop. 184 Mutex mNanoappsLock; 185 186 //! The blocking queue of incoming events from the system that have not been 187 //! distributed out to apps yet. 188 FixedSizeBlockingQueue<Event *, kMaxUnscheduledEventCount> mEvents; 189 190 // TODO: should probably be atomic to be fully correct 191 volatile bool mRunning = false; 192 193 Nanoapp *mCurrentApp = nullptr; 194 195 /** 196 * Call after when an Event has been delivered to all intended recipients. 197 * Invokes the event's free callback (if given) and releases resources. 198 * 199 * @param event The event to be freed 200 */ 201 void freeEvent(Event *event); 202 203 /** 204 * Finds a Nanoapp with the given instanceId. 205 * 206 * Only safe to call within this EventLoop's thread. 207 * 208 * @param instanceId Nanoapp instance identifier 209 * @return Nanoapp with the given instanceId, or nullptr if not found 210 */ 211 Nanoapp *lookupAppByInstanceId(uint32_t instanceId); 212}; 213 214} // namespace chre 215 216#endif // CHRE_CORE_EVENT_LOOP_H_ 217