1 /*
2  * Copyright (C) 2007 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 _LIBS_UTILS_THREAD_H
18 #define _LIBS_UTILS_THREAD_H
19 
20 #include <stdint.h>
21 #include <sys/types.h>
22 #include <time.h>
23 
24 #if !defined(_WIN32)
25 # include <pthread.h>
26 #endif
27 
28 #include <utils/Condition.h>
29 #include <utils/Errors.h>
30 #include <utils/Mutex.h>
31 #include <utils/RefBase.h>
32 #include <utils/Timers.h>
33 #include <utils/ThreadDefs.h>
34 
35 // ---------------------------------------------------------------------------
36 namespace android {
37 // ---------------------------------------------------------------------------
38 
39 // DO NOT USE: please use std::thread
40 
41 class Thread : virtual public RefBase
42 {
43 public:
44     // Create a Thread object, but doesn't create or start the associated
45     // thread. See the run() method.
46     explicit            Thread(bool canCallJava = true);
47     virtual             ~Thread();
48 
49     // Start the thread in threadLoop() which needs to be implemented.
50     // NOLINTNEXTLINE(google-default-arguments)
51     virtual status_t    run(    const char* name,
52                                 int32_t priority = PRIORITY_DEFAULT,
53                                 size_t stack = 0);
54 
55     // Ask this object's thread to exit. This function is asynchronous, when the
56     // function returns the thread might still be running. Of course, this
57     // function can be called from a different thread.
58     virtual void        requestExit();
59 
60     // Good place to do one-time initializations
61     virtual status_t    readyToRun();
62 
63     // Call requestExit() and wait until this object's thread exits.
64     // BE VERY CAREFUL of deadlocks. In particular, it would be silly to call
65     // this function from this object's thread. Will return WOULD_BLOCK in
66     // that case.
67             status_t    requestExitAndWait();
68 
69     // Wait until this object's thread exits. Returns immediately if not yet running.
70     // Do not call from this object's thread; will return WOULD_BLOCK in that case.
71             status_t    join();
72 
73     // Indicates whether this thread is running or not.
74             bool        isRunning() const;
75 
76 #if defined(__ANDROID__)
77     // Return the thread's kernel ID, same as the thread itself calling gettid(),
78     // or -1 if the thread is not running.
79             pid_t       getTid() const;
80 #endif
81 
82 protected:
83     // exitPending() returns true if requestExit() has been called.
84             bool        exitPending() const;
85 
86 private:
87     // Derived class must implement threadLoop(). The thread starts its life
88     // here. There are two ways of using the Thread object:
89     // 1) loop: if threadLoop() returns true, it will be called again if
90     //          requestExit() wasn't called.
91     // 2) once: if threadLoop() returns false, the thread will exit upon return.
92     virtual bool        threadLoop() = 0;
93 
94 private:
95     Thread& operator=(const Thread&);
96     static  int             _threadLoop(void* user);
97     const   bool            mCanCallJava;
98     // always hold mLock when reading or writing
99             thread_id_t     mThread;
100     mutable Mutex           mLock;
101             Condition       mThreadExitedCondition;
102             status_t        mStatus;
103     // note that all accesses of mExitPending and mRunning need to hold mLock
104     volatile bool           mExitPending;
105     volatile bool           mRunning;
106             sp<Thread>      mHoldSelf;
107 #if defined(__ANDROID__)
108     // legacy for debugging, not used by getTid() as it is set by the child thread
109     // and so is not initialized until the child reaches that point
110             pid_t           mTid;
111 #endif
112 };
113 
114 }  // namespace android
115 
116 // ---------------------------------------------------------------------------
117 #endif // _LIBS_UTILS_THREAD_H
118 // ---------------------------------------------------------------------------
119