1 /* 2 * Copyright (C) 2017 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 INCLUDE_PERFETTO_BASE_TASK_RUNNER_H_ 18 #define INCLUDE_PERFETTO_BASE_TASK_RUNNER_H_ 19 20 #include <functional> 21 22 #include "perfetto/base/build_config.h" 23 #include "perfetto/base/export.h" 24 #include "perfetto/base/utils.h" 25 #include "perfetto/base/watchdog.h" 26 27 namespace perfetto { 28 namespace base { 29 30 // Maximum time a single task can take in a TaskRunner before the 31 // program suicides. 32 constexpr int64_t kWatchdogMillis = 30000; // 30s 33 34 // A generic interface to allow the library clients to interleave the execution 35 // of the tracing internals in their runtime environment. 36 // The expectation is that all tasks, which are queued either via PostTask() or 37 // AddFileDescriptorWatch(), are executed on the same sequence (either on the 38 // same thread, or on a thread pool that gives sequencing guarantees). 39 // 40 // Tasks are never executed synchronously inside PostTask and there is a full 41 // memory barrier between tasks. 42 // 43 // All methods of this interface can be called from any thread. 44 class PERFETTO_EXPORT TaskRunner { 45 public: 46 virtual ~TaskRunner(); 47 48 // Schedule a task for immediate execution. Immediate tasks are always 49 // executed in the order they are posted. Can be called from any thread. 50 virtual void PostTask(std::function<void()>) = 0; 51 52 // Schedule a task for execution after |delay_ms|. Note that there is no 53 // strict ordering guarantee between immediate and delayed tasks. Can be 54 // called from any thread. 55 virtual void PostDelayedTask(std::function<void()>, uint32_t delay_ms) = 0; 56 57 // Schedule a task to run when |fd| becomes readable. The same |fd| can only 58 // be monitored by one function. Note that this function only needs to be 59 // implemented on platforms where the built-in ipc framework is used. Can be 60 // called from any thread. 61 // TODO(skyostil): Refactor this out of the shared interface. 62 virtual void AddFileDescriptorWatch(int fd, std::function<void()>) = 0; 63 64 // Remove a previously scheduled watch for |fd|. If this is run on the target 65 // thread of this TaskRunner, guarantees that the task registered to this fd 66 // will not be executed after this function call. Can be called from any 67 // thread. 68 virtual void RemoveFileDescriptorWatch(int fd) = 0; 69 70 // Checks if the current thread is the same thread where the TaskRunner's task 71 // run. This allows single threaded task runners (like the ones used in 72 // perfetto) to inform the caller that anything posted will run on the same 73 // thread/sequence. This can allow some callers to skip PostTask and instead 74 // directly execute the code. Can be called from any thread. 75 virtual bool RunsTasksOnCurrentThread() const = 0; 76 77 protected: RunTask(const std::function<void ()> & task)78 static void RunTask(const std::function<void()>& task) { 79 Watchdog::Timer handle = 80 base::Watchdog::GetInstance()->CreateFatalTimer(kWatchdogMillis); 81 task(); 82 } 83 }; 84 85 } // namespace base 86 } // namespace perfetto 87 88 #endif // INCLUDE_PERFETTO_BASE_TASK_RUNNER_H_ 89