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