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The Android Open Source Project
2009-03-03 18:28:45 -08:00
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include/utils/threads.h
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/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef _LIBS_UTILS_THREADS_H
#define _LIBS_UTILS_THREADS_H
#include <stdint.h>
#include <sys/types.h>
#include <time.h>
// ------------------------------------------------------------------
// C API
#ifdef __cplusplus
extern "C" {
#endif
typedef void* android_thread_id_t;
typedef int (*android_thread_func_t)(void*);
enum {
/*
* ***********************************************
* ** Keep in sync with android.os.Process.java **
* ***********************************************
*
* This maps directly to the "nice" priorites we use in Android.
* A thread priority should be chosen inverse-proportinally to
* the amount of work the thread is expected to do. The more work
* a thread will do, the less favorable priority it should get so that
* it doesn't starve the system. Threads not behaving properly might
* be "punished" by the kernel.
* Use the levels below when appropriate. Intermediate values are
* acceptable, preferably use the {MORE|LESS}_FAVORABLE constants below.
*/
ANDROID_PRIORITY_LOWEST = 19,
/* use for background tasks */
ANDROID_PRIORITY_BACKGROUND = 10,
/* most threads run at normal priority */
ANDROID_PRIORITY_NORMAL = 0,
/* threads currently running a UI that the user is interacting with */
ANDROID_PRIORITY_FOREGROUND = -2,
/* the main UI thread has a slightly more favorable priority */
ANDROID_PRIORITY_DISPLAY = -4,
/* ui service treads might want to run at a urgent display (uncommon) */
ANDROID_PRIORITY_URGENT_DISPLAY = -8,
/* all normal audio threads */
ANDROID_PRIORITY_AUDIO = -16,
/* service audio threads (uncommon) */
ANDROID_PRIORITY_URGENT_AUDIO = -19,
/* should never be used in practice. regular process might not
* be allowed to use this level */
ANDROID_PRIORITY_HIGHEST = -20,
ANDROID_PRIORITY_DEFAULT = ANDROID_PRIORITY_NORMAL,
ANDROID_PRIORITY_MORE_FAVORABLE = -1,
ANDROID_PRIORITY_LESS_FAVORABLE = +1,
};
// Create and run a new thread.
extern int androidCreateThread(android_thread_func_t, void *);
// Create thread with lots of parameters
extern int androidCreateThreadEtc(android_thread_func_t entryFunction,
void *userData,
const char* threadName,
int32_t threadPriority,
size_t threadStackSize,
android_thread_id_t *threadId);
// Get some sort of unique identifier for the current thread.
extern android_thread_id_t androidGetThreadId();
// Low-level thread creation -- never creates threads that can
// interact with the Java VM.
extern int androidCreateRawThreadEtc(android_thread_func_t entryFunction,
void *userData,
const char* threadName,
int32_t threadPriority,
size_t threadStackSize,
android_thread_id_t *threadId);
// Used by the Java Runtime to control how threads are created, so that
// they can be proper and lovely Java threads.
typedef int (*android_create_thread_fn)(android_thread_func_t entryFunction,
void *userData,
const char* threadName,
int32_t threadPriority,
size_t threadStackSize,
android_thread_id_t *threadId);
extern void androidSetCreateThreadFunc(android_create_thread_fn func);
#ifdef __cplusplus
}
#endif
// ------------------------------------------------------------------
// C++ API
#ifdef __cplusplus
#include <utils/Errors.h>
#include <utils/RefBase.h>
#include <utils/Timers.h>
namespace android {
typedef android_thread_id_t thread_id_t;
typedef android_thread_func_t thread_func_t;
enum {
PRIORITY_LOWEST = ANDROID_PRIORITY_LOWEST,
PRIORITY_BACKGROUND = ANDROID_PRIORITY_BACKGROUND,
PRIORITY_NORMAL = ANDROID_PRIORITY_NORMAL,
PRIORITY_FOREGROUND = ANDROID_PRIORITY_FOREGROUND,
PRIORITY_DISPLAY = ANDROID_PRIORITY_DISPLAY,
PRIORITY_URGENT_DISPLAY = ANDROID_PRIORITY_URGENT_DISPLAY,
PRIORITY_AUDIO = ANDROID_PRIORITY_AUDIO,
PRIORITY_URGENT_AUDIO = ANDROID_PRIORITY_URGENT_AUDIO,
PRIORITY_HIGHEST = ANDROID_PRIORITY_HIGHEST,
PRIORITY_DEFAULT = ANDROID_PRIORITY_DEFAULT,
PRIORITY_MORE_FAVORABLE = ANDROID_PRIORITY_MORE_FAVORABLE,
PRIORITY_LESS_FAVORABLE = ANDROID_PRIORITY_LESS_FAVORABLE,
};
// Create and run a new thread.
inline bool createThread(thread_func_t f, void *a) {
return androidCreateThread(f, a) ? true : false;
}
// Create thread with lots of parameters
inline bool createThreadEtc(thread_func_t entryFunction,
void *userData,
const char* threadName = "android:unnamed_thread",
int32_t threadPriority = PRIORITY_DEFAULT,
size_t threadStackSize = 0,
thread_id_t *threadId = 0)
{
return androidCreateThreadEtc(entryFunction, userData, threadName,
threadPriority, threadStackSize, threadId) ? true : false;
}
// Get some sort of unique identifier for the current thread.
inline thread_id_t getThreadId() {
return androidGetThreadId();
}
/*
* Simple mutex class. The implementation is system-dependent.
*
* The mutex must be unlocked by the thread that locked it. They are not
* recursive, i.e. the same thread can't lock it multiple times.
*/
class Mutex {
public:
Mutex();
Mutex(const char* name);
~Mutex();
// lock or unlock the mutex
status_t lock();
void unlock();
// lock if possible; returns 0 on success, error otherwise
status_t tryLock();
// Manages the mutex automatically. It'll be locked when Autolock is
// constructed and released when Autolock goes out of scope.
class Autolock {
public:
inline Autolock(Mutex& mutex) : mpMutex(&mutex) { mutex.lock(); }
inline Autolock(Mutex* mutex) : mpMutex(mutex) { mutex->lock(); }
inline ~Autolock() { mpMutex->unlock(); }
private:
Mutex* mpMutex;
};
private:
friend class Condition;
// A mutex cannot be copied
Mutex(const Mutex&);
Mutex& operator = (const Mutex&);
void _init();
void* mState;
};
/*
* Automatic mutex. Declare one of these at the top of a function.
* When the function returns, it will go out of scope, and release the
* mutex.
*/
typedef Mutex::Autolock AutoMutex;
/*
* Condition variable class. The implementation is system-dependent.
*
* Condition variables are paired up with mutexes. Lock the mutex,
* call wait(), then either re-wait() if things aren't quite what you want,
* or unlock the mutex and continue. All threads calling wait() must
* use the same mutex for a given Condition.
*/
class Condition {
public:
Condition();
~Condition();
// Wait on the condition variable. Lock the mutex before calling.
status_t wait(Mutex& mutex);
// Wait on the condition variable until the given time. Lock the mutex
// before calling.
status_t wait(Mutex& mutex, nsecs_t abstime);
// same with relative timeout
status_t waitRelative(Mutex& mutex, nsecs_t reltime);
// Signal the condition variable, allowing one thread to continue.
void signal();
// Signal the condition variable, allowing all threads to continue.
void broadcast();
private:
void* mState;
};
/*
* Read/write lock. The resource can have multiple readers or one writer,
* but can't be read and written at the same time.
*
* The same thread should not call a lock function while it already has
* a lock. (Should be okay for multiple readers.)
*/
class ReadWriteLock {
public:
ReadWriteLock()
: mNumReaders(0), mNumWriters(0)
{}
~ReadWriteLock() {}
void lockForRead();
bool tryLockForRead();
void unlockForRead();
void lockForWrite();
bool tryLockForWrite();
void unlockForWrite();
private:
int mNumReaders;
int mNumWriters;
Mutex mLock;
Condition mReadWaiter;
Condition mWriteWaiter;
#if defined(PRINT_RENDER_TIMES)
DurationTimer mDebugTimer;
#endif
};
/*
* This is our spiffy thread object!
*/
class Thread : virtual public RefBase
{
public:
// Create a Thread object, but doesn't create or start the associated
// thread. See the run() method.
Thread(bool canCallJava = true);
virtual ~Thread();
// Start the thread in threadLoop() which needs to be implemented.
virtual status_t run( const char* name = 0,
int32_t priority = PRIORITY_DEFAULT,
size_t stack = 0);
// Ask this object's thread to exit. This function is asynchronous, when the
// function returns the thread might still be running. Of course, this
// function can be called from a different thread.
virtual void requestExit();
// Good place to do one-time initializations
virtual status_t readyToRun();
// Call requestExit() and wait until this object's thread exits.
// BE VERY CAREFUL of deadlocks. In particular, it would be silly to call
// this function from this object's thread. Will return WOULD_BLOCK in
// that case.
status_t requestExitAndWait();
protected:
// exitPending() returns true if requestExit() has been called.
bool exitPending() const;
private:
// Derived class must implemtent threadLoop(). The thread starts its life
// here. There are two ways of using the Thread object:
// 1) loop: if threadLoop() returns true, it will be called again if
// requestExit() wasn't called.
// 2) once: if threadLoop() returns false, the thread will exit upon return.
virtual bool threadLoop() = 0;
private:
Thread& operator=(const Thread&);
static int _threadLoop(void* user);
const bool mCanCallJava;
thread_id_t mThread;
Mutex mLock;
Condition mThreadExitedCondition;
status_t mStatus;
volatile bool mExitPending;
volatile bool mRunning;
sp<Thread> mHoldSelf;
};
}; // namespace android
#endif // __cplusplus
#endif // _LIBS_UTILS_THREADS_H