event_loop.h revision 9d5b500a223ef73560f0dce38f50b809bde5dd0d
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 * Invokes the Nanoapp's start callback, and if successful, adds it to the 77 * set of Nanoapps managed by this EventLoop. This function must only be 78 * called from the context of the thread that runs this event loop (i.e. from 79 * the same thread that will call run() or from a callback invoked within 80 * run()). 81 * 82 * @param nanoapp The nanoapp that will be started. Upon success, this 83 * UniquePtr will become invalid, as the underlying Nanoapp instance 84 * will have been transferred to be managed by this EventLoop. 85 * @return true if the app was started successfully 86 */ 87 bool startNanoapp(UniquePtr<Nanoapp>& nanoapp); 88 89 /** 90 * Stops a nanoapp by invoking the stop entry point. The nanoapp passed in 91 * must have been previously started by the startNanoapp method. 92 * 93 * @param A pointer to the nanoapp to stop. 94 */ 95 void stopNanoapp(Nanoapp *nanoapp); 96 97 /** 98 * Executes the loop that blocks on the event queue and delivers received 99 * events to nanoapps. Only returns after stop() is called (from another 100 * context). 101 */ 102 void run(); 103 104 /** 105 * Signals the event loop currently executing in run() to exit gracefully at 106 * the next available opportunity. This function is thread-safe. 107 */ 108 void stop(); 109 110 /** 111 * Posts an event to a nanoapp that is currently running (or all nanoapps if 112 * the target instance ID is kBroadcastInstanceId). 113 * 114 * This function is safe to call from any thread. 115 * 116 * @param The type of data being posted. 117 * @param The data being posted. 118 * @param The callback to invoke when the event is no longer needed. 119 * @param The instance ID of the sender of this event. 120 * @param The instance ID of the destination of this event. 121 * 122 * @return true if the event was successfully added to the queue 123 */ 124 bool postEvent(uint16_t eventType, void *eventData, 125 chreEventCompleteFunction *freeCallback, 126 uint32_t senderInstanceId = kSystemInstanceId, 127 uint32_t targetInstanceId = kBroadcastInstanceId); 128 129 /** 130 * Returns a pointer to the currently executing Nanoapp, or nullptr if none is 131 * currently executing. Must only be called from within the thread context 132 * associated with this EventLoop. 133 * 134 * @return the currently executing nanoapp, or nullptr 135 */ 136 Nanoapp *getCurrentNanoapp() const; 137 138 /** 139 * Gets the number of nanoapps currently associated with this event loop. Must 140 * only be called within the context of this EventLoop. 141 * 142 * @return The number of nanoapps managed by this event loop 143 */ 144 size_t getNanoappCount() const; 145 146 /** 147 * Obtains the TimerPool associated with this event loop. 148 * 149 * @return The timer pool owned by this event loop. 150 */ 151 TimerPool& getTimerPool(); 152 153 /** 154 * Searches the set of nanoapps managed by this EventLoop for one with the 155 * given instance ID. 156 * 157 * This function is safe to call from any thread. 158 * 159 * @param instanceId The nanoapp instance ID to search for. 160 * @return a pointer to the found nanoapp or nullptr if no match was found. 161 */ 162 Nanoapp *findNanoappByInstanceId(uint32_t instanceId); 163 164 private: 165 //! The maximum number of events that can be active in the system. 166 static constexpr size_t kMaxEventCount = 1024; 167 168 //! The maximum number of events that are awaiting to be scheduled. These 169 //! events are in a queue to be distributed to apps. 170 static constexpr size_t kMaxUnscheduledEventCount = 1024; 171 172 //! The memory pool to allocate incoming events from. 173 SynchronizedMemoryPool<Event, kMaxEventCount> mEventPool; 174 175 //! The timer used schedule timed events for tasks running in this event loop. 176 TimerPool mTimerPool; 177 178 //! The list of nanoapps managed by this event loop. 179 DynamicVector<UniquePtr<Nanoapp>> mNanoapps; 180 181 //! This lock *must* be held whenever we: 182 //! (1) make changes to the mNanoapps vector, or 183 //! (2) read the mNanoapps vector from a thread other than the one 184 //! associated with this EventLoop 185 //! It is not necessary to acquire the lock when reading mNanoapps from within 186 //! the thread context of this EventLoop. 187 Mutex mNanoappsLock; 188 189 //! The blocking queue of incoming events from the system that have not been 190 //! distributed out to apps yet. 191 FixedSizeBlockingQueue<Event *, kMaxUnscheduledEventCount> mEvents; 192 193 // TODO: should probably be atomic to be fully correct 194 volatile bool mRunning = false; 195 196 Nanoapp *mCurrentApp = nullptr; 197 198 /** 199 * Call after when an Event has been delivered to all intended recipients. 200 * Invokes the event's free callback (if given) and releases resources. 201 * 202 * @param event The event to be freed 203 */ 204 void freeEvent(Event *event); 205 206 /** 207 * Finds a Nanoapp with the given instanceId. 208 * 209 * Only safe to call within this EventLoop's thread. 210 * 211 * @param instanceId Nanoapp instance identifier 212 * @return Nanoapp with the given instanceId, or nullptr if not found 213 */ 214 Nanoapp *lookupAppByInstanceId(uint32_t instanceId); 215}; 216 217} // namespace chre 218 219#endif // CHRE_CORE_EVENT_LOOP_H_ 220