libs/utils/Threads.cpp - platform/frameworks/base - Gitiles

 /*
  * 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.
  */

 // #define LOG_NDEBUG 0
 #define LOG_TAG "libutils.threads"

 #include <utils/threads.h>
 #include <utils/Log.h>

 #include <stdio.h>
 #include <stdlib.h>
 #include <memory.h>
 #include <errno.h>
 #include <assert.h>
 #include <unistd.h>

 #if defined(HAVE_PTHREADS)
 # include <pthread.h>
 # include <sched.h>
 # include <sys/resource.h>
 #elif defined(HAVE_WIN32_THREADS)
 # include <windows.h>
 # include <stdint.h>
 # include <process.h>
 # define HAVE_CREATETHREAD  // Cygwin, vs. HAVE__BEGINTHREADEX for MinGW
 #endif

 #if defined(HAVE_PRCTL)
 #include <sys/prctl.h>
 #endif

 /*
  * ===========================================================================
  *      Thread wrappers
  * ===========================================================================
  */

 using namespace android;

 // ----------------------------------------------------------------------------
 #if defined(HAVE_PTHREADS)
 // ----------------------------------------------------------------------------

 /*
  * Create and run a new thead.
  *
  * We create it "detached", so it cleans up after itself.
  */

 typedef void* (*android_pthread_entry)(void*);

 struct thread_data_t {
     thread_func_t   entryFunction;
     void*           userData;
     int             priority;
     char *          threadName;

     // we use this trampoline when we need to set the priority with
     // nice/setpriority.
     static int trampoline(const thread_data_t* t) {
         thread_func_t f = t->entryFunction;
         void* u = t->userData;
         int prio = t->priority;
         char * name = t->threadName;
         delete t;
         setpriority(PRIO_PROCESS, 0, prio);
         if (name) {
 #if defined(HAVE_PRCTL)
             // Mac OS doesn't have this, and we build libutil for the host too
             int hasAt = 0;
             int hasDot = 0;
             char *s = name;
             while (*s) {
                 if (*s == '.') hasDot = 1;
                 else if (*s == '@') hasAt = 1;
                 s++;
             }
             int len = s - name;
             if (len < 15 || hasAt || !hasDot) {
                 s = name;
             } else {
                 s = name + len - 15;
             }
             prctl(PR_SET_NAME, (unsigned long) s, 0, 0, 0);
 #endif
             free(name);
         }
         return f(u);
     }
 };

 int androidCreateRawThreadEtc(android_thread_func_t entryFunction,
                                void *userData,
                                const char* threadName,
                                int32_t threadPriority,
                                size_t threadStackSize,
                                android_thread_id_t *threadId)
 {
     pthread_attr_t attr;
     pthread_attr_init(&attr);
     pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

 #ifdef HAVE_ANDROID_OS  /* valgrind is rejecting RT-priority create reqs */
     if (threadPriority != PRIORITY_DEFAULT || threadName != NULL) {
         // We could avoid the trampoline if there was a way to get to the
         // android_thread_id_t (pid) from pthread_t
         thread_data_t* t = new thread_data_t;
         t->priority = threadPriority;
         t->threadName = threadName ? strdup(threadName) : NULL;
         t->entryFunction = entryFunction;
         t->userData = userData;
         entryFunction = (android_thread_func_t)&thread_data_t::trampoline;
         userData = t;
     }
 #endif

     if (threadStackSize) {
         pthread_attr_setstacksize(&attr, threadStackSize);
     }

     errno = 0;
     pthread_t thread;
     int result = pthread_create(&thread, &attr,
                     (android_pthread_entry)entryFunction, userData);
     if (result != 0) {
         LOGE("androidCreateRawThreadEtc failed (entry=%p, res=%d, errno=%d)\n"
              "(android threadPriority=%d)",
             entryFunction, result, errno, threadPriority);
         return 0;
     }

     if (threadId != NULL) {
         *threadId = (android_thread_id_t)thread; // XXX: this is not portable
     }
     return 1;
 }

 android_thread_id_t androidGetThreadId()
 {
     return (android_thread_id_t)pthread_self();
 }

 // ----------------------------------------------------------------------------
 #elif defined(HAVE_WIN32_THREADS)
 // ----------------------------------------------------------------------------

 /*
  * Trampoline to make us __stdcall-compliant.
  *
  * We're expected to delete "vDetails" when we're done.
  */
 struct threadDetails {
     int (*func)(void*);
     void* arg;
 };
 static __stdcall unsigned int threadIntermediary(void* vDetails)
 {
     struct threadDetails* pDetails = (struct threadDetails*) vDetails;
     int result;

     result = (*(pDetails->func))(pDetails->arg);

     delete pDetails;

     LOG(LOG_VERBOSE, "thread", "thread exiting\n");
     return (unsigned int) result;
 }

 /*
  * Create and run a new thread.
  */
 static bool doCreateThread(android_thread_func_t fn, void* arg, android_thread_id_t *id)
 {
     HANDLE hThread;
     struct threadDetails* pDetails = new threadDetails; // must be on heap
     unsigned int thrdaddr;

     pDetails->func = fn;
     pDetails->arg = arg;

 #if defined(HAVE__BEGINTHREADEX)
     hThread = (HANDLE) _beginthreadex(NULL, 0, threadIntermediary, pDetails, 0,
                     &thrdaddr);
     if (hThread == 0)
 #elif defined(HAVE_CREATETHREAD)
     hThread = CreateThread(NULL, 0,
                     (LPTHREAD_START_ROUTINE) threadIntermediary,
                     (void*) pDetails, 0, (DWORD*) &thrdaddr);
     if (hThread == NULL)
 #endif
     {
         LOG(LOG_WARN, "thread", "WARNING: thread create failed\n");
         return false;
     }

 #if defined(HAVE_CREATETHREAD)
     /* close the management handle */
     CloseHandle(hThread);
 #endif

     if (id != NULL) {
       	*id = (android_thread_id_t)thrdaddr;
     }

     return true;
 }

 int androidCreateRawThreadEtc(android_thread_func_t fn,
                                void *userData,
                                const char* threadName,
                                int32_t threadPriority,
                                size_t threadStackSize,
                                android_thread_id_t *threadId)
 {
     return doCreateThread(  fn, userData, threadId);
 }

 android_thread_id_t androidGetThreadId()
 {
     return (android_thread_id_t)GetCurrentThreadId();
 }

 // ----------------------------------------------------------------------------
 #else
 #error "Threads not supported"
 #endif

 // ----------------------------------------------------------------------------

 int androidCreateThread(android_thread_func_t fn, void* arg)
 {
     return createThreadEtc(fn, arg);
 }

 int androidCreateThreadGetID(android_thread_func_t fn, void *arg, android_thread_id_t *id)
 {
     return createThreadEtc(fn, arg, "android:unnamed_thread",
                            PRIORITY_DEFAULT, 0, id);
 }

 static android_create_thread_fn gCreateThreadFn = androidCreateRawThreadEtc;

 int androidCreateThreadEtc(android_thread_func_t entryFunction,
                             void *userData,
                             const char* threadName,
                             int32_t threadPriority,
                             size_t threadStackSize,
                             android_thread_id_t *threadId)
 {
     return gCreateThreadFn(entryFunction, userData, threadName,
         threadPriority, threadStackSize, threadId);
 }

 void androidSetCreateThreadFunc(android_create_thread_fn func)
 {
     gCreateThreadFn = func;
 }

 namespace android {

 /*
  * ===========================================================================
  *      Mutex class
  * ===========================================================================
  */

 #if defined(HAVE_PTHREADS)
 // implemented as inlines in threads.h
 #elif defined(HAVE_WIN32_THREADS)

 Mutex::Mutex()
 {
     HANDLE hMutex;

     assert(sizeof(hMutex) == sizeof(mState));

     hMutex = CreateMutex(NULL, FALSE, NULL);
     mState = (void*) hMutex;
 }

 Mutex::Mutex(const char* name)
 {
     // XXX: name not used for now
     HANDLE hMutex;

     assert(sizeof(hMutex) == sizeof(mState));

     hMutex = CreateMutex(NULL, FALSE, NULL);
     mState = (void*) hMutex;
 }

 Mutex::Mutex(int type, const char* name)
 {
     // XXX: type and name not used for now
     HANDLE hMutex;

     assert(sizeof(hMutex) == sizeof(mState));

     hMutex = CreateMutex(NULL, FALSE, NULL);
     mState = (void*) hMutex;
 }

 Mutex::~Mutex()
 {
     CloseHandle((HANDLE) mState);
 }

 status_t Mutex::lock()
 {
     DWORD dwWaitResult;
     dwWaitResult = WaitForSingleObject((HANDLE) mState, INFINITE);
     return dwWaitResult != WAIT_OBJECT_0 ? -1 : NO_ERROR;
 }

 void Mutex::unlock()
 {
     if (!ReleaseMutex((HANDLE) mState))
         LOG(LOG_WARN, "thread", "WARNING: bad result from unlocking mutex\n");
 }

 status_t Mutex::tryLock()
 {
     DWORD dwWaitResult;

     dwWaitResult = WaitForSingleObject((HANDLE) mState, 0);
     if (dwWaitResult != WAIT_OBJECT_0 && dwWaitResult != WAIT_TIMEOUT)
         LOG(LOG_WARN, "thread", "WARNING: bad result from try-locking mutex\n");
     return (dwWaitResult == WAIT_OBJECT_0) ? 0 : -1;
 }

 #else
 #error "Somebody forgot to implement threads for this platform."
 #endif


 /*
  * ===========================================================================
  *      Condition class
  * ===========================================================================
  */

 #if defined(HAVE_PTHREADS)
 // implemented as inlines in threads.h
 #elif defined(HAVE_WIN32_THREADS)

 /*
  * Windows doesn't have a condition variable solution.  It's possible
  * to create one, but it's easy to get it wrong.  For a discussion, and
  * the origin of this implementation, see:
  *
  *  http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
  *
  * The implementation shown on the page does NOT follow POSIX semantics.
  * As an optimization they require acquiring the external mutex before
  * calling signal() and broadcast(), whereas POSIX only requires grabbing
  * it before calling wait().  The implementation here has been un-optimized
  * to have the correct behavior.
  */
 typedef struct WinCondition {
     // Number of waiting threads.
     int                 waitersCount;

     // Serialize access to waitersCount.
     CRITICAL_SECTION    waitersCountLock;

     // Semaphore used to queue up threads waiting for the condition to
     // become signaled.
     HANDLE              sema;

     // An auto-reset event used by the broadcast/signal thread to wait
     // for all the waiting thread(s) to wake up and be released from
     // the semaphore.
     HANDLE              waitersDone;

     // This mutex wouldn't be necessary if we required that the caller
     // lock the external mutex before calling signal() and broadcast().
     // I'm trying to mimic pthread semantics though.
     HANDLE              internalMutex;

     // Keeps track of whether we were broadcasting or signaling.  This
     // allows us to optimize the code if we're just signaling.
     bool                wasBroadcast;

     status_t wait(WinCondition* condState, HANDLE hMutex, nsecs_t* abstime)
     {
         // Increment the wait count, avoiding race conditions.
         EnterCriticalSection(&condState->waitersCountLock);
         condState->waitersCount++;
         //printf("+++ wait: incr waitersCount to %d (tid=%ld)\n",
         //    condState->waitersCount, getThreadId());
         LeaveCriticalSection(&condState->waitersCountLock);

         DWORD timeout = INFINITE;
         if (abstime) {
             nsecs_t reltime = *abstime - systemTime();
             if (reltime < 0)
                 reltime = 0;
             timeout = reltime/1000000;
         }

         // Atomically release the external mutex and wait on the semaphore.
         DWORD res =
             SignalObjectAndWait(hMutex, condState->sema, timeout, FALSE);

         //printf("+++ wait: awake (tid=%ld)\n", getThreadId());

         // Reacquire lock to avoid race conditions.
         EnterCriticalSection(&condState->waitersCountLock);

         // No longer waiting.
         condState->waitersCount--;

         // Check to see if we're the last waiter after a broadcast.
         bool lastWaiter = (condState->wasBroadcast && condState->waitersCount == 0);

         //printf("+++ wait: lastWaiter=%d (wasBc=%d wc=%d)\n",
         //    lastWaiter, condState->wasBroadcast, condState->waitersCount);

         LeaveCriticalSection(&condState->waitersCountLock);

         // If we're the last waiter thread during this particular broadcast
         // then signal broadcast() that we're all awake.  It'll drop the
         // internal mutex.
         if (lastWaiter) {
             // Atomically signal the "waitersDone" event and wait until we
             // can acquire the internal mutex.  We want to do this in one step
             // because it ensures that everybody is in the mutex FIFO before
             // any thread has a chance to run.  Without it, another thread
             // could wake up, do work, and hop back in ahead of us.
             SignalObjectAndWait(condState->waitersDone, condState->internalMutex,
                 INFINITE, FALSE);
         } else {
             // Grab the internal mutex.
             WaitForSingleObject(condState->internalMutex, INFINITE);
         }

         // Release the internal and grab the external.
         ReleaseMutex(condState->internalMutex);
         WaitForSingleObject(hMutex, INFINITE);

         return res == WAIT_OBJECT_0 ? NO_ERROR : -1;
     }
 } WinCondition;

 /*
  * Constructor.  Set up the WinCondition stuff.
  */
 Condition::Condition()
 {
     WinCondition* condState = new WinCondition;

     condState->waitersCount = 0;
     condState->wasBroadcast = false;
     // semaphore: no security, initial value of 0
     condState->sema = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
     InitializeCriticalSection(&condState->waitersCountLock);
     // auto-reset event, not signaled initially
     condState->waitersDone = CreateEvent(NULL, FALSE, FALSE, NULL);
     // used so we don't have to lock external mutex on signal/broadcast
     condState->internalMutex = CreateMutex(NULL, FALSE, NULL);

     mState = condState;
 }

 /*
  * Destructor.  Free Windows resources as well as our allocated storage.
  */
 Condition::~Condition()
 {
     WinCondition* condState = (WinCondition*) mState;
     if (condState != NULL) {
         CloseHandle(condState->sema);
         CloseHandle(condState->waitersDone);
         delete condState;
     }
 }


 status_t Condition::wait(Mutex& mutex)
 {
     WinCondition* condState = (WinCondition*) mState;
     HANDLE hMutex = (HANDLE) mutex.mState;

     return ((WinCondition*)mState)->wait(condState, hMutex, NULL);
 }

 status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime)
 {
     WinCondition* condState = (WinCondition*) mState;
     HANDLE hMutex = (HANDLE) mutex.mState;
     nsecs_t absTime = systemTime()+reltime;

     return ((WinCondition*)mState)->wait(condState, hMutex, &absTime);
 }

 /*
  * Signal the condition variable, allowing one thread to continue.
  */
 void Condition::signal()
 {
     WinCondition* condState = (WinCondition*) mState;

     // Lock the internal mutex.  This ensures that we don't clash with
     // broadcast().
     WaitForSingleObject(condState->internalMutex, INFINITE);

     EnterCriticalSection(&condState->waitersCountLock);
     bool haveWaiters = (condState->waitersCount > 0);
     LeaveCriticalSection(&condState->waitersCountLock);

     // If no waiters, then this is a no-op.  Otherwise, knock the semaphore
     // down a notch.
     if (haveWaiters)
         ReleaseSemaphore(condState->sema, 1, 0);

     // Release internal mutex.
     ReleaseMutex(condState->internalMutex);
 }

 /*
  * Signal the condition variable, allowing all threads to continue.
  *
  * First we have to wake up all threads waiting on the semaphore, then
  * we wait until all of the threads have actually been woken before
  * releasing the internal mutex.  This ensures that all threads are woken.
  */
 void Condition::broadcast()
 {
     WinCondition* condState = (WinCondition*) mState;

     // Lock the internal mutex.  This keeps the guys we're waking up
     // from getting too far.
     WaitForSingleObject(condState->internalMutex, INFINITE);

     EnterCriticalSection(&condState->waitersCountLock);
     bool haveWaiters = false;

     if (condState->waitersCount > 0) {
         haveWaiters = true;
         condState->wasBroadcast = true;
     }

     if (haveWaiters) {
         // Wake up all the waiters.
         ReleaseSemaphore(condState->sema, condState->waitersCount, 0);

         LeaveCriticalSection(&condState->waitersCountLock);

         // Wait for all awakened threads to acquire the counting semaphore.
         // The last guy who was waiting sets this.
         WaitForSingleObject(condState->waitersDone, INFINITE);

         // Reset wasBroadcast.  (No crit section needed because nobody
         // else can wake up to poke at it.)
         condState->wasBroadcast = 0;
     } else {
         // nothing to do
         LeaveCriticalSection(&condState->waitersCountLock);
     }

     // Release internal mutex.
     ReleaseMutex(condState->internalMutex);
 }

 #else
 #error "condition variables not supported on this platform"
 #endif

 // ----------------------------------------------------------------------------

 /*
  * This is our thread object!
  */

 Thread::Thread(bool canCallJava)
     :   mCanCallJava(canCallJava),
         mThread(thread_id_t(-1)),
         mLock("Thread::mLock"),
         mStatus(NO_ERROR),
         mExitPending(false), mRunning(false)
 {
 }

 Thread::~Thread()
 {
 }

 status_t Thread::readyToRun()
 {
     return NO_ERROR;
 }

 status_t Thread::run(const char* name, int32_t priority, size_t stack)
 {
     Mutex::Autolock _l(mLock);

     if (mRunning) {
         // thread already started
         return INVALID_OPERATION;
     }

     // reset status and exitPending to their default value, so we can
     // try again after an error happened (either below, or in readyToRun())
     mStatus = NO_ERROR;
     mExitPending = false;
     mThread = thread_id_t(-1);

     // hold a strong reference on ourself
     mHoldSelf = this;

     mRunning = true;

     bool res;
     if (mCanCallJava) {
         res = createThreadEtc(_threadLoop,
                 this, name, priority, stack, &mThread);
     } else {
         res = androidCreateRawThreadEtc(_threadLoop,
                 this, name, priority, stack, &mThread);
     }

     if (res == false) {
         mStatus = UNKNOWN_ERROR;   // something happened!
         mRunning = false;
         mThread = thread_id_t(-1);
         mHoldSelf.clear();  // "this" may have gone away after this.

         return UNKNOWN_ERROR;
     }

     // Do not refer to mStatus here: The thread is already running (may, in fact
     // already have exited with a valid mStatus result). The NO_ERROR indication
     // here merely indicates successfully starting the thread and does not
     // imply successful termination/execution.
     return NO_ERROR;
 }

 int Thread::_threadLoop(void* user)
 {
     Thread* const self = static_cast<Thread*>(user);
     sp<Thread> strong(self->mHoldSelf);
     wp<Thread> weak(strong);
     self->mHoldSelf.clear();

 #if HAVE_ANDROID_OS
     // this is very useful for debugging with gdb
     self->mTid = gettid();
 #endif

     bool first = true;

     do {
         bool result;
         if (first) {
             first = false;
             self->mStatus = self->readyToRun();
             result = (self->mStatus == NO_ERROR);

             if (result && !self->mExitPending) {
                 // Binder threads (and maybe others) rely on threadLoop
                 // running at least once after a successful ::readyToRun()
                 // (unless, of course, the thread has already been asked to exit
                 // at that point).
                 // This is because threads are essentially used like this:
                 //   (new ThreadSubclass())->run();
                 // The caller therefore does not retain a strong reference to
                 // the thread and the thread would simply disappear after the
                 // successful ::readyToRun() call instead of entering the
                 // threadLoop at least once.
                 result = self->threadLoop();
             }
         } else {
             result = self->threadLoop();
         }

         if (result == false || self->mExitPending) {
             self->mExitPending = true;
             self->mLock.lock();
             self->mRunning = false;
             self->mThreadExitedCondition.broadcast();
             self->mLock.unlock();
             break;
         }

         // Release our strong reference, to let a chance to the thread
         // to die a peaceful death.
         strong.clear();
         // And immediately, re-acquire a strong reference for the next loop
         strong = weak.promote();
     } while(strong != 0);

     return 0;
 }

 void Thread::requestExit()
 {
     mExitPending = true;
 }

 status_t Thread::requestExitAndWait()
 {
     if (mThread == getThreadId()) {
         LOGW(
         "Thread (this=%p): don't call waitForExit() from this "
         "Thread object's thread. It's a guaranteed deadlock!",
         this);

         return WOULD_BLOCK;
     }

     requestExit();

     Mutex::Autolock _l(mLock);
     while (mRunning == true) {
         mThreadExitedCondition.wait(mLock);
     }
     mExitPending = false;

     return mStatus;
 }

 bool Thread::exitPending() const
 {
     return mExitPending;
 }


 };  // namespace android
	/*
	* 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.
	*/

	// #define LOG_NDEBUG 0
	#define LOG_TAG "libutils.threads"

	#include <utils/threads.h>
	#include <utils/Log.h>

	#include <stdio.h>
	#include <stdlib.h>
	#include <memory.h>
	#include <errno.h>
	#include <assert.h>
	#include <unistd.h>

	#if defined(HAVE_PTHREADS)
	# include <pthread.h>
	# include <sched.h>
	# include <sys/resource.h>
	#elif defined(HAVE_WIN32_THREADS)
	# include <windows.h>
	# include <stdint.h>
	# include <process.h>
	# define HAVE_CREATETHREAD // Cygwin, vs. HAVE__BEGINTHREADEX for MinGW
	#endif

	#if defined(HAVE_PRCTL)
	#include <sys/prctl.h>
	#endif

	/*
	* ===========================================================================
	* Thread wrappers
	* ===========================================================================
	*/

	using namespace android;

	// ----------------------------------------------------------------------------
	#if defined(HAVE_PTHREADS)
	// ----------------------------------------------------------------------------

	/*
	* Create and run a new thead.
	*
	* We create it "detached", so it cleans up after itself.
	*/

	typedef void* (android_pthread_entry)(void);

	struct thread_data_t {
	thread_func_t entryFunction;
	void* userData;
	int priority;
	char * threadName;

	// we use this trampoline when we need to set the priority with
	// nice/setpriority.
	static int trampoline(const thread_data_t* t) {
	thread_func_t f = t->entryFunction;
	void* u = t->userData;
	int prio = t->priority;
	char * name = t->threadName;
	delete t;
	setpriority(PRIO_PROCESS, 0, prio);
	if (name) {
	#if defined(HAVE_PRCTL)
	// Mac OS doesn't have this, and we build libutil for the host too
	int hasAt = 0;
	int hasDot = 0;
	char *s = name;
	while (*s) {
	if (*s == '.') hasDot = 1;
	else if (*s == '@') hasAt = 1;
	s++;
	}
	int len = s - name;
	if (len < 15 \|\| hasAt \|\| !hasDot) {
	s = name;
	} else {
	s = name + len - 15;
	}
	prctl(PR_SET_NAME, (unsigned long) s, 0, 0, 0);
	#endif
	free(name);
	}
	return f(u);
	}
	};

	int androidCreateRawThreadEtc(android_thread_func_t entryFunction,
	void *userData,
	const char* threadName,
	int32_t threadPriority,
	size_t threadStackSize,
	android_thread_id_t *threadId)
	{
	pthread_attr_t attr;
	pthread_attr_init(&attr);
	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

	#ifdef HAVE_ANDROID_OS /* valgrind is rejecting RT-priority create reqs */
	if (threadPriority != PRIORITY_DEFAULT \|\| threadName != NULL) {
	// We could avoid the trampoline if there was a way to get to the
	// android_thread_id_t (pid) from pthread_t
	thread_data_t* t = new thread_data_t;
	t->priority = threadPriority;
	t->threadName = threadName ? strdup(threadName) : NULL;
	t->entryFunction = entryFunction;
	t->userData = userData;
	entryFunction = (android_thread_func_t)&thread_data_t::trampoline;
	userData = t;
	}
	#endif

	if (threadStackSize) {
	pthread_attr_setstacksize(&attr, threadStackSize);
	}

	errno = 0;
	pthread_t thread;
	int result = pthread_create(&thread, &attr,
	(android_pthread_entry)entryFunction, userData);
	if (result != 0) {
	LOGE("androidCreateRawThreadEtc failed (entry=%p, res=%d, errno=%d)\n"
	"(android threadPriority=%d)",
	entryFunction, result, errno, threadPriority);
	return 0;
	}

	if (threadId != NULL) {
	*threadId = (android_thread_id_t)thread; // XXX: this is not portable
	}
	return 1;
	}

	android_thread_id_t androidGetThreadId()
	{
	return (android_thread_id_t)pthread_self();
	}

	// ----------------------------------------------------------------------------
	#elif defined(HAVE_WIN32_THREADS)
	// ----------------------------------------------------------------------------

	/*
	* Trampoline to make us __stdcall-compliant.
	*
	* We're expected to delete "vDetails" when we're done.
	*/
	struct threadDetails {
	int (func)(void);
	void* arg;
	};
	static __stdcall unsigned int threadIntermediary(void* vDetails)
	{
	struct threadDetails* pDetails = (struct threadDetails*) vDetails;
	int result;

	result = (*(pDetails->func))(pDetails->arg);

	delete pDetails;

	LOG(LOG_VERBOSE, "thread", "thread exiting\n");
	return (unsigned int) result;
	}

	/*
	* Create and run a new thread.
	*/
	static bool doCreateThread(android_thread_func_t fn, void* arg, android_thread_id_t *id)
	{
	HANDLE hThread;
	struct threadDetails* pDetails = new threadDetails; // must be on heap
	unsigned int thrdaddr;

	pDetails->func = fn;
	pDetails->arg = arg;

	#if defined(HAVE__BEGINTHREADEX)
	hThread = (HANDLE) _beginthreadex(NULL, 0, threadIntermediary, pDetails, 0,
	&thrdaddr);
	if (hThread == 0)
	#elif defined(HAVE_CREATETHREAD)
	hThread = CreateThread(NULL, 0,
	(LPTHREAD_START_ROUTINE) threadIntermediary,
	(void) pDetails, 0, (DWORD) &thrdaddr);
	if (hThread == NULL)
	#endif
	{
	LOG(LOG_WARN, "thread", "WARNING: thread create failed\n");
	return false;
	}

	#if defined(HAVE_CREATETHREAD)
	/* close the management handle */
	CloseHandle(hThread);
	#endif

	if (id != NULL) {
	*id = (android_thread_id_t)thrdaddr;
	}

	return true;
	}

	int androidCreateRawThreadEtc(android_thread_func_t fn,
	void *userData,
	const char* threadName,
	int32_t threadPriority,
	size_t threadStackSize,
	android_thread_id_t *threadId)
	{
	return doCreateThread( fn, userData, threadId);
	}

	android_thread_id_t androidGetThreadId()
	{
	return (android_thread_id_t)GetCurrentThreadId();
	}

	// ----------------------------------------------------------------------------
	#else
	#error "Threads not supported"
	#endif

	// ----------------------------------------------------------------------------

	int androidCreateThread(android_thread_func_t fn, void* arg)
	{
	return createThreadEtc(fn, arg);
	}

	int androidCreateThreadGetID(android_thread_func_t fn, void arg, android_thread_id_t id)
	{
	return createThreadEtc(fn, arg, "android:unnamed_thread",
	PRIORITY_DEFAULT, 0, id);
	}

	static android_create_thread_fn gCreateThreadFn = androidCreateRawThreadEtc;

	int androidCreateThreadEtc(android_thread_func_t entryFunction,
	void *userData,
	const char* threadName,
	int32_t threadPriority,
	size_t threadStackSize,
	android_thread_id_t *threadId)
	{
	return gCreateThreadFn(entryFunction, userData, threadName,
	threadPriority, threadStackSize, threadId);
	}

	void androidSetCreateThreadFunc(android_create_thread_fn func)
	{
	gCreateThreadFn = func;
	}

	namespace android {

	/*
	* ===========================================================================
	* Mutex class
	* ===========================================================================
	*/

	#if defined(HAVE_PTHREADS)
	// implemented as inlines in threads.h
	#elif defined(HAVE_WIN32_THREADS)

	Mutex::Mutex()
	{
	HANDLE hMutex;

	assert(sizeof(hMutex) == sizeof(mState));

	hMutex = CreateMutex(NULL, FALSE, NULL);
	mState = (void*) hMutex;
	}

	Mutex::Mutex(const char* name)
	{
	// XXX: name not used for now
	HANDLE hMutex;

	assert(sizeof(hMutex) == sizeof(mState));

	hMutex = CreateMutex(NULL, FALSE, NULL);
	mState = (void*) hMutex;
	}

	Mutex::Mutex(int type, const char* name)
	{
	// XXX: type and name not used for now
	HANDLE hMutex;

	assert(sizeof(hMutex) == sizeof(mState));

	hMutex = CreateMutex(NULL, FALSE, NULL);
	mState = (void*) hMutex;
	}

	Mutex::~Mutex()
	{
	CloseHandle((HANDLE) mState);
	}

	status_t Mutex::lock()
	{
	DWORD dwWaitResult;
	dwWaitResult = WaitForSingleObject((HANDLE) mState, INFINITE);
	return dwWaitResult != WAIT_OBJECT_0 ? -1 : NO_ERROR;
	}

	void Mutex::unlock()
	{
	if (!ReleaseMutex((HANDLE) mState))
	LOG(LOG_WARN, "thread", "WARNING: bad result from unlocking mutex\n");
	}

	status_t Mutex::tryLock()
	{
	DWORD dwWaitResult;

	dwWaitResult = WaitForSingleObject((HANDLE) mState, 0);
	if (dwWaitResult != WAIT_OBJECT_0 && dwWaitResult != WAIT_TIMEOUT)
	LOG(LOG_WARN, "thread", "WARNING: bad result from try-locking mutex\n");
	return (dwWaitResult == WAIT_OBJECT_0) ? 0 : -1;
	}

	#else
	#error "Somebody forgot to implement threads for this platform."
	#endif


	/*
	* ===========================================================================
	* Condition class
	* ===========================================================================
	*/

	#if defined(HAVE_PTHREADS)
	// implemented as inlines in threads.h
	#elif defined(HAVE_WIN32_THREADS)

	/*
	* Windows doesn't have a condition variable solution. It's possible
	* to create one, but it's easy to get it wrong. For a discussion, and
	* the origin of this implementation, see:
	*
	* http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
	*
	* The implementation shown on the page does NOT follow POSIX semantics.
	* As an optimization they require acquiring the external mutex before
	* calling signal() and broadcast(), whereas POSIX only requires grabbing
	* it before calling wait(). The implementation here has been un-optimized
	* to have the correct behavior.
	*/
	typedef struct WinCondition {
	// Number of waiting threads.
	int waitersCount;

	// Serialize access to waitersCount.
	CRITICAL_SECTION waitersCountLock;

	// Semaphore used to queue up threads waiting for the condition to
	// become signaled.
	HANDLE sema;

	// An auto-reset event used by the broadcast/signal thread to wait
	// for all the waiting thread(s) to wake up and be released from
	// the semaphore.
	HANDLE waitersDone;

	// This mutex wouldn't be necessary if we required that the caller
	// lock the external mutex before calling signal() and broadcast().
	// I'm trying to mimic pthread semantics though.
	HANDLE internalMutex;

	// Keeps track of whether we were broadcasting or signaling. This
	// allows us to optimize the code if we're just signaling.
	bool wasBroadcast;

	status_t wait(WinCondition* condState, HANDLE hMutex, nsecs_t* abstime)
	{
	// Increment the wait count, avoiding race conditions.
	EnterCriticalSection(&condState->waitersCountLock);
	condState->waitersCount++;
	//printf("+++ wait: incr waitersCount to %d (tid=%ld)\n",
	// condState->waitersCount, getThreadId());
	LeaveCriticalSection(&condState->waitersCountLock);

	DWORD timeout = INFINITE;
	if (abstime) {
	nsecs_t reltime = *abstime - systemTime();
	if (reltime < 0)
	reltime = 0;
	timeout = reltime/1000000;
	}

	// Atomically release the external mutex and wait on the semaphore.
	DWORD res =
	SignalObjectAndWait(hMutex, condState->sema, timeout, FALSE);

	//printf("+++ wait: awake (tid=%ld)\n", getThreadId());

	// Reacquire lock to avoid race conditions.
	EnterCriticalSection(&condState->waitersCountLock);

	// No longer waiting.
	condState->waitersCount--;

	// Check to see if we're the last waiter after a broadcast.
	bool lastWaiter = (condState->wasBroadcast && condState->waitersCount == 0);

	//printf("+++ wait: lastWaiter=%d (wasBc=%d wc=%d)\n",
	// lastWaiter, condState->wasBroadcast, condState->waitersCount);

	LeaveCriticalSection(&condState->waitersCountLock);

	// If we're the last waiter thread during this particular broadcast
	// then signal broadcast() that we're all awake. It'll drop the
	// internal mutex.
	if (lastWaiter) {
	// Atomically signal the "waitersDone" event and wait until we
	// can acquire the internal mutex. We want to do this in one step
	// because it ensures that everybody is in the mutex FIFO before
	// any thread has a chance to run. Without it, another thread
	// could wake up, do work, and hop back in ahead of us.
	SignalObjectAndWait(condState->waitersDone, condState->internalMutex,
	INFINITE, FALSE);
	} else {
	// Grab the internal mutex.
	WaitForSingleObject(condState->internalMutex, INFINITE);
	}

	// Release the internal and grab the external.
	ReleaseMutex(condState->internalMutex);
	WaitForSingleObject(hMutex, INFINITE);

	return res == WAIT_OBJECT_0 ? NO_ERROR : -1;
	}
	} WinCondition;

	/*
	* Constructor. Set up the WinCondition stuff.
	*/
	Condition::Condition()
	{
	WinCondition* condState = new WinCondition;

	condState->waitersCount = 0;
	condState->wasBroadcast = false;
	// semaphore: no security, initial value of 0
	condState->sema = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
	InitializeCriticalSection(&condState->waitersCountLock);
	// auto-reset event, not signaled initially
	condState->waitersDone = CreateEvent(NULL, FALSE, FALSE, NULL);
	// used so we don't have to lock external mutex on signal/broadcast
	condState->internalMutex = CreateMutex(NULL, FALSE, NULL);

	mState = condState;
	}

	/*
	* Destructor. Free Windows resources as well as our allocated storage.
	*/
	Condition::~Condition()
	{
	WinCondition* condState = (WinCondition*) mState;
	if (condState != NULL) {
	CloseHandle(condState->sema);
	CloseHandle(condState->waitersDone);
	delete condState;
	}
	}


	status_t Condition::wait(Mutex& mutex)
	{
	WinCondition* condState = (WinCondition*) mState;
	HANDLE hMutex = (HANDLE) mutex.mState;

	return ((WinCondition*)mState)->wait(condState, hMutex, NULL);
	}

	status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime)
	{
	WinCondition* condState = (WinCondition*) mState;
	HANDLE hMutex = (HANDLE) mutex.mState;
	nsecs_t absTime = systemTime()+reltime;

	return ((WinCondition*)mState)->wait(condState, hMutex, &absTime);
	}

	/*
	* Signal the condition variable, allowing one thread to continue.
	*/
	void Condition::signal()
	{
	WinCondition* condState = (WinCondition*) mState;

	// Lock the internal mutex. This ensures that we don't clash with
	// broadcast().
	WaitForSingleObject(condState->internalMutex, INFINITE);

	EnterCriticalSection(&condState->waitersCountLock);
	bool haveWaiters = (condState->waitersCount > 0);
	LeaveCriticalSection(&condState->waitersCountLock);

	// If no waiters, then this is a no-op. Otherwise, knock the semaphore
	// down a notch.
	if (haveWaiters)
	ReleaseSemaphore(condState->sema, 1, 0);

	// Release internal mutex.
	ReleaseMutex(condState->internalMutex);
	}

	/*
	* Signal the condition variable, allowing all threads to continue.
	*
	* First we have to wake up all threads waiting on the semaphore, then
	* we wait until all of the threads have actually been woken before
	* releasing the internal mutex. This ensures that all threads are woken.
	*/
	void Condition::broadcast()
	{
	WinCondition* condState = (WinCondition*) mState;

	// Lock the internal mutex. This keeps the guys we're waking up
	// from getting too far.
	WaitForSingleObject(condState->internalMutex, INFINITE);

	EnterCriticalSection(&condState->waitersCountLock);
	bool haveWaiters = false;

	if (condState->waitersCount > 0) {
	haveWaiters = true;
	condState->wasBroadcast = true;
	}

	if (haveWaiters) {
	// Wake up all the waiters.
	ReleaseSemaphore(condState->sema, condState->waitersCount, 0);

	LeaveCriticalSection(&condState->waitersCountLock);

	// Wait for all awakened threads to acquire the counting semaphore.
	// The last guy who was waiting sets this.
	WaitForSingleObject(condState->waitersDone, INFINITE);

	// Reset wasBroadcast. (No crit section needed because nobody
	// else can wake up to poke at it.)
	condState->wasBroadcast = 0;
	} else {
	// nothing to do
	LeaveCriticalSection(&condState->waitersCountLock);
	}

	// Release internal mutex.
	ReleaseMutex(condState->internalMutex);
	}

	#else
	#error "condition variables not supported on this platform"
	#endif

	// ----------------------------------------------------------------------------

	/*
	* This is our thread object!
	*/

	Thread::Thread(bool canCallJava)
	: mCanCallJava(canCallJava),
	mThread(thread_id_t(-1)),
	mLock("Thread::mLock"),
	mStatus(NO_ERROR),
	mExitPending(false), mRunning(false)
	{
	}

	Thread::~Thread()
	{
	}

	status_t Thread::readyToRun()
	{
	return NO_ERROR;
	}

	status_t Thread::run(const char* name, int32_t priority, size_t stack)
	{
	Mutex::Autolock _l(mLock);

	if (mRunning) {
	// thread already started
	return INVALID_OPERATION;
	}

	// reset status and exitPending to their default value, so we can
	// try again after an error happened (either below, or in readyToRun())
	mStatus = NO_ERROR;
	mExitPending = false;
	mThread = thread_id_t(-1);

	// hold a strong reference on ourself
	mHoldSelf = this;

	mRunning = true;

	bool res;
	if (mCanCallJava) {
	res = createThreadEtc(_threadLoop,
	this, name, priority, stack, &mThread);
	} else {
	res = androidCreateRawThreadEtc(_threadLoop,
	this, name, priority, stack, &mThread);
	}

	if (res == false) {
	mStatus = UNKNOWN_ERROR; // something happened!
	mRunning = false;
	mThread = thread_id_t(-1);
	mHoldSelf.clear(); // "this" may have gone away after this.

	return UNKNOWN_ERROR;
	}

	// Do not refer to mStatus here: The thread is already running (may, in fact
	// already have exited with a valid mStatus result). The NO_ERROR indication
	// here merely indicates successfully starting the thread and does not
	// imply successful termination/execution.
	return NO_ERROR;
	}

	int Thread::_threadLoop(void* user)
	{
	Thread* const self = static_cast<Thread*>(user);
	sp<Thread> strong(self->mHoldSelf);
	wp<Thread> weak(strong);
	self->mHoldSelf.clear();

	#if HAVE_ANDROID_OS
	// this is very useful for debugging with gdb
	self->mTid = gettid();
	#endif

	bool first = true;

	do {
	bool result;
	if (first) {
	first = false;
	self->mStatus = self->readyToRun();
	result = (self->mStatus == NO_ERROR);

	if (result && !self->mExitPending) {
	// Binder threads (and maybe others) rely on threadLoop
	// running at least once after a successful ::readyToRun()
	// (unless, of course, the thread has already been asked to exit
	// at that point).
	// This is because threads are essentially used like this:
	// (new ThreadSubclass())->run();
	// The caller therefore does not retain a strong reference to
	// the thread and the thread would simply disappear after the
	// successful ::readyToRun() call instead of entering the
	// threadLoop at least once.
	result = self->threadLoop();
	}
	} else {
	result = self->threadLoop();
	}

	if (result == false \|\| self->mExitPending) {
	self->mExitPending = true;
	self->mLock.lock();
	self->mRunning = false;
	self->mThreadExitedCondition.broadcast();
	self->mLock.unlock();
	break;
	}

	// Release our strong reference, to let a chance to the thread
	// to die a peaceful death.
	strong.clear();
	// And immediately, re-acquire a strong reference for the next loop
	strong = weak.promote();
	} while(strong != 0);

	return 0;
	}

	void Thread::requestExit()
	{
	mExitPending = true;
	}

	status_t Thread::requestExitAndWait()
	{
	if (mThread == getThreadId()) {
	LOGW(
	"Thread (this=%p): don't call waitForExit() from this "
	"Thread object's thread. It's a guaranteed deadlock!",
	this);

	return WOULD_BLOCK;
	}

	requestExit();

	Mutex::Autolock _l(mLock);
	while (mRunning == true) {
	mThreadExitedCondition.wait(mLock);
	}
	mExitPending = false;

	return mStatus;
	}

	bool Thread::exitPending() const
	{
	return mExitPending;
	}



	}; // namespace android