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     virtual status_t    run(    const char* name,
51                                 int32_t priority = PRIORITY_DEFAULT,
52                                 size_t stack = 0);
53 
54     // Ask this object's thread to exit. This function is asynchronous, when the
55     // function returns the thread might still be running. Of course, this
56     // function can be called from a different thread.
57     virtual void        requestExit();
58 
59     // Good place to do one-time initializations
60     virtual status_t    readyToRun();
61 
62     // Call requestExit() and wait until this object's thread exits.
63     // BE VERY CAREFUL of deadlocks. In particular, it would be silly to call
64     // this function from this object's thread. Will return WOULD_BLOCK in
65     // that case.
66             status_t    requestExitAndWait();
67 
68     // Wait until this object's thread exits. Returns immediately if not yet running.
69     // Do not call from this object's thread; will return WOULD_BLOCK in that case.
70             status_t    join();
71 
72     // Indicates whether this thread is running or not.
73             bool        isRunning() const;
74 
75 #if defined(__ANDROID__)
76     // Return the thread's kernel ID, same as the thread itself calling gettid(),
77     // or -1 if the thread is not running.
78             pid_t       getTid() const;
79 #endif
80 
81 protected:
82     // exitPending() returns true if requestExit() has been called.
83             bool        exitPending() const;
84 
85 private:
86     // Derived class must implement threadLoop(). The thread starts its life
87     // here. There are two ways of using the Thread object:
88     // 1) loop: if threadLoop() returns true, it will be called again if
89     //          requestExit() wasn't called.
90     // 2) once: if threadLoop() returns false, the thread will exit upon return.
91     virtual bool        threadLoop() = 0;
92 
93 private:
94     Thread& operator=(const Thread&);
95     static  int             _threadLoop(void* user);
96     const   bool            mCanCallJava;
97     // always hold mLock when reading or writing
98             thread_id_t     mThread;
99     mutable Mutex           mLock;
100             Condition       mThreadExitedCondition;
101             status_t        mStatus;
102     // note that all accesses of mExitPending and mRunning need to hold mLock
103     volatile bool           mExitPending;
104     volatile bool           mRunning;
105             sp<Thread>      mHoldSelf;
106 #if defined(__ANDROID__)
107     // legacy for debugging, not used by getTid() as it is set by the child thread
108     // and so is not initialized until the child reaches that point
109             pid_t           mTid;
110 #endif
111 };
112 
113 
114 }; // namespace android
115 
116 // ---------------------------------------------------------------------------
117 #endif // _LIBS_UTILS_THREAD_H
118 // ---------------------------------------------------------------------------
119