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      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_UNIX_TASK_RUNNER_H_
     18 #define INCLUDE_PERFETTO_BASE_UNIX_TASK_RUNNER_H_
     19 
     20 #include "perfetto/base/build_config.h"
     21 #include "perfetto/base/event.h"
     22 #include "perfetto/base/scoped_file.h"
     23 #include "perfetto/base/task_runner.h"
     24 #include "perfetto/base/thread_checker.h"
     25 #include "perfetto/base/thread_utils.h"
     26 #include "perfetto/base/time.h"
     27 
     28 #include <poll.h>
     29 #include <chrono>
     30 #include <deque>
     31 #include <map>
     32 #include <mutex>
     33 #include <vector>
     34 
     35 namespace perfetto {
     36 namespace base {
     37 
     38 // Runs a task runner on the current thread.
     39 //
     40 // Implementation note: we currently assume (and enforce in debug builds) that
     41 // Run() is called from the thread that constructed the UnixTaskRunner. This is
     42 // not strictly necessary, and we could instead track the thread that invokes
     43 // Run(). However, a related property that *might* be important to enforce is
     44 // that the destructor runs on the task-running thread. Otherwise, if there are
     45 // still-pending tasks at the time of destruction, we would destroy those
     46 // outside of the task thread (which might be unexpected to the caller). On the
     47 // other hand, the std::function task interface discourages use of any
     48 // resource-owning tasks (as the callable needs to be copyable), so this might
     49 // not be important in practice.
     50 //
     51 // TODO(rsavitski): consider adding a thread-check in the destructor, after
     52 // auditing existing usages.
     53 class UnixTaskRunner : public TaskRunner {
     54  public:
     55   UnixTaskRunner();
     56   ~UnixTaskRunner() override;
     57 
     58   // Start executing tasks. Doesn't return until Quit() is called. Run() may be
     59   // called multiple times on the same task runner.
     60   void Run();
     61   void Quit();
     62 
     63   // Checks whether there are any pending immediate tasks to run. Note that
     64   // delayed tasks don't count even if they are due to run.
     65   bool IsIdleForTesting();
     66 
     67   // TaskRunner implementation:
     68   void PostTask(std::function<void()>) override;
     69   void PostDelayedTask(std::function<void()>, uint32_t delay_ms) override;
     70   void AddFileDescriptorWatch(int fd, std::function<void()>) override;
     71   void RemoveFileDescriptorWatch(int fd) override;
     72   bool RunsTasksOnCurrentThread() const override;
     73 
     74   // Returns true if the task runner is quitting, or has quit and hasn't been
     75   // restarted since. Exposed primarily for ThreadTaskRunner, not necessary for
     76   // normal use of this class.
     77   bool QuitCalled();
     78 
     79  private:
     80   void WakeUp();
     81 
     82   void UpdateWatchTasksLocked();
     83 
     84   int GetDelayMsToNextTaskLocked() const;
     85   void RunImmediateAndDelayedTask();
     86   void PostFileDescriptorWatches();
     87   void RunFileDescriptorWatch(int fd);
     88 
     89   ThreadChecker thread_checker_;
     90   PlatformThreadID created_thread_id_ = GetThreadId();
     91 
     92   // On Linux, an eventfd(2) used to waking up the task runner when a new task
     93   // is posted. Otherwise the read end of a pipe used for the same purpose.
     94   Event event_;
     95 
     96   std::vector<struct pollfd> poll_fds_;
     97 
     98   // --- Begin lock-protected members ---
     99 
    100   std::mutex lock_;
    101 
    102   std::deque<std::function<void()>> immediate_tasks_;
    103   std::multimap<TimeMillis, std::function<void()>> delayed_tasks_;
    104   bool quit_ = false;
    105 
    106   struct WatchTask {
    107     std::function<void()> callback;
    108     size_t poll_fd_index;  // Index into |poll_fds_|.
    109   };
    110 
    111   std::map<int, WatchTask> watch_tasks_;
    112   bool watch_tasks_changed_ = false;
    113 
    114   // --- End lock-protected members ---
    115 };
    116 
    117 }  // namespace base
    118 }  // namespace perfetto
    119 
    120 #endif  // INCLUDE_PERFETTO_BASE_UNIX_TASK_RUNNER_H_
    121