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// #define LOG_NDEBUG 0 18#define LOG_TAG "libutils.threads" 19 20#include <utils/threads.h> 21#include <utils/Log.h> 22 23#include <cutils/sched_policy.h> 24#include <cutils/properties.h> 25 26#include <stdio.h> 27#include <stdlib.h> 28#include <memory.h> 29#include <errno.h> 30#include <assert.h> 31#include <unistd.h> 32 33#if defined(HAVE_PTHREADS) 34# include <pthread.h> 35# include <sched.h> 36# include <sys/resource.h> 37#ifdef HAVE_ANDROID_OS 38# include <bionic_pthread.h> 39#endif 40#elif defined(HAVE_WIN32_THREADS) 41# include <windows.h> 42# include <stdint.h> 43# include <process.h> 44# define HAVE_CREATETHREAD // Cygwin, vs. HAVE__BEGINTHREADEX for MinGW 45#endif 46 47#if defined(HAVE_PRCTL) 48#include <sys/prctl.h> 49#endif 50 51/* 52 * =========================================================================== 53 * Thread wrappers 54 * =========================================================================== 55 */ 56 57using namespace android; 58 59// ---------------------------------------------------------------------------- 60#if defined(HAVE_PTHREADS) 61// ---------------------------------------------------------------------------- 62 63/* 64 * Create and run a new thread. 65 * 66 * We create it "detached", so it cleans up after itself. 67 */ 68 69typedef void* (*android_pthread_entry)(void*); 70 71static pthread_once_t gDoSchedulingGroupOnce = PTHREAD_ONCE_INIT; 72static bool gDoSchedulingGroup = true; 73 74static void checkDoSchedulingGroup(void) { 75 char buf[PROPERTY_VALUE_MAX]; 76 int len = property_get("debug.sys.noschedgroups", buf, ""); 77 if (len > 0) { 78 int temp; 79 if (sscanf(buf, "%d", &temp) == 1) { 80 gDoSchedulingGroup = temp == 0; 81 } 82 } 83} 84 85struct thread_data_t { 86 thread_func_t entryFunction; 87 void* userData; 88 int priority; 89 char * threadName; 90 91 // we use this trampoline when we need to set the priority with 92 // nice/setpriority, and name with prctl. 93 static int trampoline(const thread_data_t* t) { 94 thread_func_t f = t->entryFunction; 95 void* u = t->userData; 96 int prio = t->priority; 97 char * name = t->threadName; 98 delete t; 99 setpriority(PRIO_PROCESS, 0, prio); 100 pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup); 101 if (gDoSchedulingGroup) { 102 if (prio >= ANDROID_PRIORITY_BACKGROUND) { 103 set_sched_policy(androidGetTid(), SP_BACKGROUND); 104 } else if (prio > ANDROID_PRIORITY_AUDIO) { 105 set_sched_policy(androidGetTid(), SP_FOREGROUND); 106 } else { 107 // defaults to that of parent, or as set by requestPriority() 108 } 109 } 110 111 if (name) { 112#if defined(HAVE_PRCTL) 113 // Mac OS doesn't have this, and we build libutil for the host too 114 int hasAt = 0; 115 int hasDot = 0; 116 char *s = name; 117 while (*s) { 118 if (*s == '.') hasDot = 1; 119 else if (*s == '@') hasAt = 1; 120 s++; 121 } 122 int len = s - name; 123 if (len < 15 || hasAt || !hasDot) { 124 s = name; 125 } else { 126 s = name + len - 15; 127 } 128 prctl(PR_SET_NAME, (unsigned long) s, 0, 0, 0); 129#endif 130 free(name); 131 } 132 return f(u); 133 } 134}; 135 136int androidCreateRawThreadEtc(android_thread_func_t entryFunction, 137 void *userData, 138 const char* threadName, 139 int32_t threadPriority, 140 size_t threadStackSize, 141 android_thread_id_t *threadId) 142{ 143 pthread_attr_t attr; 144 pthread_attr_init(&attr); 145 pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); 146 147#ifdef HAVE_ANDROID_OS /* valgrind is rejecting RT-priority create reqs */ 148 if (threadPriority != PRIORITY_DEFAULT || threadName != NULL) { 149 // Now that the pthread_t has a method to find the associated 150 // android_thread_id_t (pid) from pthread_t, it would be possible to avoid 151 // this trampoline in some cases as the parent could set the properties 152 // for the child. However, there would be a race condition because the 153 // child becomes ready immediately, and it doesn't work for the name. 154 // prctl(PR_SET_NAME) only works for self; prctl(PR_SET_THREAD_NAME) was 155 // proposed but not yet accepted. 156 thread_data_t* t = new thread_data_t; 157 t->priority = threadPriority; 158 t->threadName = threadName ? strdup(threadName) : NULL; 159 t->entryFunction = entryFunction; 160 t->userData = userData; 161 entryFunction = (android_thread_func_t)&thread_data_t::trampoline; 162 userData = t; 163 } 164#endif 165 166 if (threadStackSize) { 167 pthread_attr_setstacksize(&attr, threadStackSize); 168 } 169 170 errno = 0; 171 pthread_t thread; 172 int result = pthread_create(&thread, &attr, 173 (android_pthread_entry)entryFunction, userData); 174 pthread_attr_destroy(&attr); 175 if (result != 0) { 176 ALOGE("androidCreateRawThreadEtc failed (entry=%p, res=%d, errno=%d)\n" 177 "(android threadPriority=%d)", 178 entryFunction, result, errno, threadPriority); 179 return 0; 180 } 181 182 // Note that *threadID is directly available to the parent only, as it is 183 // assigned after the child starts. Use memory barrier / lock if the child 184 // or other threads also need access. 185 if (threadId != NULL) { 186 *threadId = (android_thread_id_t)thread; // XXX: this is not portable 187 } 188 return 1; 189} 190 191#ifdef HAVE_ANDROID_OS 192static pthread_t android_thread_id_t_to_pthread(android_thread_id_t thread) 193{ 194 return (pthread_t) thread; 195} 196#endif 197 198android_thread_id_t androidGetThreadId() 199{ 200 return (android_thread_id_t)pthread_self(); 201} 202 203// ---------------------------------------------------------------------------- 204#elif defined(HAVE_WIN32_THREADS) 205// ---------------------------------------------------------------------------- 206 207/* 208 * Trampoline to make us __stdcall-compliant. 209 * 210 * We're expected to delete "vDetails" when we're done. 211 */ 212struct threadDetails { 213 int (*func)(void*); 214 void* arg; 215}; 216static __stdcall unsigned int threadIntermediary(void* vDetails) 217{ 218 struct threadDetails* pDetails = (struct threadDetails*) vDetails; 219 int result; 220 221 result = (*(pDetails->func))(pDetails->arg); 222 223 delete pDetails; 224 225 ALOG(LOG_VERBOSE, "thread", "thread exiting\n"); 226 return (unsigned int) result; 227} 228 229/* 230 * Create and run a new thread. 231 */ 232static bool doCreateThread(android_thread_func_t fn, void* arg, android_thread_id_t *id) 233{ 234 HANDLE hThread; 235 struct threadDetails* pDetails = new threadDetails; // must be on heap 236 unsigned int thrdaddr; 237 238 pDetails->func = fn; 239 pDetails->arg = arg; 240 241#if defined(HAVE__BEGINTHREADEX) 242 hThread = (HANDLE) _beginthreadex(NULL, 0, threadIntermediary, pDetails, 0, 243 &thrdaddr); 244 if (hThread == 0) 245#elif defined(HAVE_CREATETHREAD) 246 hThread = CreateThread(NULL, 0, 247 (LPTHREAD_START_ROUTINE) threadIntermediary, 248 (void*) pDetails, 0, (DWORD*) &thrdaddr); 249 if (hThread == NULL) 250#endif 251 { 252 ALOG(LOG_WARN, "thread", "WARNING: thread create failed\n"); 253 return false; 254 } 255 256#if defined(HAVE_CREATETHREAD) 257 /* close the management handle */ 258 CloseHandle(hThread); 259#endif 260 261 if (id != NULL) { 262 *id = (android_thread_id_t)thrdaddr; 263 } 264 265 return true; 266} 267 268int androidCreateRawThreadEtc(android_thread_func_t fn, 269 void *userData, 270 const char* threadName, 271 int32_t threadPriority, 272 size_t threadStackSize, 273 android_thread_id_t *threadId) 274{ 275 return doCreateThread( fn, userData, threadId); 276} 277 278android_thread_id_t androidGetThreadId() 279{ 280 return (android_thread_id_t)GetCurrentThreadId(); 281} 282 283// ---------------------------------------------------------------------------- 284#else 285#error "Threads not supported" 286#endif 287 288// ---------------------------------------------------------------------------- 289 290int androidCreateThread(android_thread_func_t fn, void* arg) 291{ 292 return createThreadEtc(fn, arg); 293} 294 295int androidCreateThreadGetID(android_thread_func_t fn, void *arg, android_thread_id_t *id) 296{ 297 return createThreadEtc(fn, arg, "android:unnamed_thread", 298 PRIORITY_DEFAULT, 0, id); 299} 300 301static android_create_thread_fn gCreateThreadFn = androidCreateRawThreadEtc; 302 303int androidCreateThreadEtc(android_thread_func_t entryFunction, 304 void *userData, 305 const char* threadName, 306 int32_t threadPriority, 307 size_t threadStackSize, 308 android_thread_id_t *threadId) 309{ 310 return gCreateThreadFn(entryFunction, userData, threadName, 311 threadPriority, threadStackSize, threadId); 312} 313 314void androidSetCreateThreadFunc(android_create_thread_fn func) 315{ 316 gCreateThreadFn = func; 317} 318 319pid_t androidGetTid() 320{ 321#ifdef HAVE_GETTID 322 return gettid(); 323#else 324 return getpid(); 325#endif 326} 327 328#ifdef HAVE_ANDROID_OS 329int androidSetThreadPriority(pid_t tid, int pri) 330{ 331 int rc = 0; 332 333#if defined(HAVE_PTHREADS) 334 int lasterr = 0; 335 336 pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup); 337 if (gDoSchedulingGroup) { 338 // set_sched_policy does not support tid == 0 339 int policy_tid; 340 if (tid == 0) { 341 policy_tid = androidGetTid(); 342 } else { 343 policy_tid = tid; 344 } 345 if (pri >= ANDROID_PRIORITY_BACKGROUND) { 346 rc = set_sched_policy(policy_tid, SP_BACKGROUND); 347 } else if (getpriority(PRIO_PROCESS, tid) >= ANDROID_PRIORITY_BACKGROUND) { 348 rc = set_sched_policy(policy_tid, SP_FOREGROUND); 349 } 350 } 351 352 if (rc) { 353 lasterr = errno; 354 } 355 356 if (setpriority(PRIO_PROCESS, tid, pri) < 0) { 357 rc = INVALID_OPERATION; 358 } else { 359 errno = lasterr; 360 } 361#endif 362 363 return rc; 364} 365 366int androidGetThreadPriority(pid_t tid) { 367#if defined(HAVE_PTHREADS) 368 return getpriority(PRIO_PROCESS, tid); 369#else 370 return ANDROID_PRIORITY_NORMAL; 371#endif 372} 373 374#endif 375 376namespace android { 377 378/* 379 * =========================================================================== 380 * Mutex class 381 * =========================================================================== 382 */ 383 384#if defined(HAVE_PTHREADS) 385// implemented as inlines in threads.h 386#elif defined(HAVE_WIN32_THREADS) 387 388Mutex::Mutex() 389{ 390 HANDLE hMutex; 391 392 assert(sizeof(hMutex) == sizeof(mState)); 393 394 hMutex = CreateMutex(NULL, FALSE, NULL); 395 mState = (void*) hMutex; 396} 397 398Mutex::Mutex(const char* name) 399{ 400 // XXX: name not used for now 401 HANDLE hMutex; 402 403 assert(sizeof(hMutex) == sizeof(mState)); 404 405 hMutex = CreateMutex(NULL, FALSE, NULL); 406 mState = (void*) hMutex; 407} 408 409Mutex::Mutex(int type, const char* name) 410{ 411 // XXX: type and name not used for now 412 HANDLE hMutex; 413 414 assert(sizeof(hMutex) == sizeof(mState)); 415 416 hMutex = CreateMutex(NULL, FALSE, NULL); 417 mState = (void*) hMutex; 418} 419 420Mutex::~Mutex() 421{ 422 CloseHandle((HANDLE) mState); 423} 424 425status_t Mutex::lock() 426{ 427 DWORD dwWaitResult; 428 dwWaitResult = WaitForSingleObject((HANDLE) mState, INFINITE); 429 return dwWaitResult != WAIT_OBJECT_0 ? -1 : NO_ERROR; 430} 431 432void Mutex::unlock() 433{ 434 if (!ReleaseMutex((HANDLE) mState)) 435 ALOG(LOG_WARN, "thread", "WARNING: bad result from unlocking mutex\n"); 436} 437 438status_t Mutex::tryLock() 439{ 440 DWORD dwWaitResult; 441 442 dwWaitResult = WaitForSingleObject((HANDLE) mState, 0); 443 if (dwWaitResult != WAIT_OBJECT_0 && dwWaitResult != WAIT_TIMEOUT) 444 ALOG(LOG_WARN, "thread", "WARNING: bad result from try-locking mutex\n"); 445 return (dwWaitResult == WAIT_OBJECT_0) ? 0 : -1; 446} 447 448#else 449#error "Somebody forgot to implement threads for this platform." 450#endif 451 452 453/* 454 * =========================================================================== 455 * Condition class 456 * =========================================================================== 457 */ 458 459#if defined(HAVE_PTHREADS) 460// implemented as inlines in threads.h 461#elif defined(HAVE_WIN32_THREADS) 462 463/* 464 * Windows doesn't have a condition variable solution. It's possible 465 * to create one, but it's easy to get it wrong. For a discussion, and 466 * the origin of this implementation, see: 467 * 468 * http://www.cs.wustl.edu/~schmidt/win32-cv-1.html 469 * 470 * The implementation shown on the page does NOT follow POSIX semantics. 471 * As an optimization they require acquiring the external mutex before 472 * calling signal() and broadcast(), whereas POSIX only requires grabbing 473 * it before calling wait(). The implementation here has been un-optimized 474 * to have the correct behavior. 475 */ 476typedef struct WinCondition { 477 // Number of waiting threads. 478 int waitersCount; 479 480 // Serialize access to waitersCount. 481 CRITICAL_SECTION waitersCountLock; 482 483 // Semaphore used to queue up threads waiting for the condition to 484 // become signaled. 485 HANDLE sema; 486 487 // An auto-reset event used by the broadcast/signal thread to wait 488 // for all the waiting thread(s) to wake up and be released from 489 // the semaphore. 490 HANDLE waitersDone; 491 492 // This mutex wouldn't be necessary if we required that the caller 493 // lock the external mutex before calling signal() and broadcast(). 494 // I'm trying to mimic pthread semantics though. 495 HANDLE internalMutex; 496 497 // Keeps track of whether we were broadcasting or signaling. This 498 // allows us to optimize the code if we're just signaling. 499 bool wasBroadcast; 500 501 status_t wait(WinCondition* condState, HANDLE hMutex, nsecs_t* abstime) 502 { 503 // Increment the wait count, avoiding race conditions. 504 EnterCriticalSection(&condState->waitersCountLock); 505 condState->waitersCount++; 506 //printf("+++ wait: incr waitersCount to %d (tid=%ld)\n", 507 // condState->waitersCount, getThreadId()); 508 LeaveCriticalSection(&condState->waitersCountLock); 509 510 DWORD timeout = INFINITE; 511 if (abstime) { 512 nsecs_t reltime = *abstime - systemTime(); 513 if (reltime < 0) 514 reltime = 0; 515 timeout = reltime/1000000; 516 } 517 518 // Atomically release the external mutex and wait on the semaphore. 519 DWORD res = 520 SignalObjectAndWait(hMutex, condState->sema, timeout, FALSE); 521 522 //printf("+++ wait: awake (tid=%ld)\n", getThreadId()); 523 524 // Reacquire lock to avoid race conditions. 525 EnterCriticalSection(&condState->waitersCountLock); 526 527 // No longer waiting. 528 condState->waitersCount--; 529 530 // Check to see if we're the last waiter after a broadcast. 531 bool lastWaiter = (condState->wasBroadcast && condState->waitersCount == 0); 532 533 //printf("+++ wait: lastWaiter=%d (wasBc=%d wc=%d)\n", 534 // lastWaiter, condState->wasBroadcast, condState->waitersCount); 535 536 LeaveCriticalSection(&condState->waitersCountLock); 537 538 // If we're the last waiter thread during this particular broadcast 539 // then signal broadcast() that we're all awake. It'll drop the 540 // internal mutex. 541 if (lastWaiter) { 542 // Atomically signal the "waitersDone" event and wait until we 543 // can acquire the internal mutex. We want to do this in one step 544 // because it ensures that everybody is in the mutex FIFO before 545 // any thread has a chance to run. Without it, another thread 546 // could wake up, do work, and hop back in ahead of us. 547 SignalObjectAndWait(condState->waitersDone, condState->internalMutex, 548 INFINITE, FALSE); 549 } else { 550 // Grab the internal mutex. 551 WaitForSingleObject(condState->internalMutex, INFINITE); 552 } 553 554 // Release the internal and grab the external. 555 ReleaseMutex(condState->internalMutex); 556 WaitForSingleObject(hMutex, INFINITE); 557 558 return res == WAIT_OBJECT_0 ? NO_ERROR : -1; 559 } 560} WinCondition; 561 562/* 563 * Constructor. Set up the WinCondition stuff. 564 */ 565Condition::Condition() 566{ 567 WinCondition* condState = new WinCondition; 568 569 condState->waitersCount = 0; 570 condState->wasBroadcast = false; 571 // semaphore: no security, initial value of 0 572 condState->sema = CreateSemaphore(NULL, 0, 0x7fffffff, NULL); 573 InitializeCriticalSection(&condState->waitersCountLock); 574 // auto-reset event, not signaled initially 575 condState->waitersDone = CreateEvent(NULL, FALSE, FALSE, NULL); 576 // used so we don't have to lock external mutex on signal/broadcast 577 condState->internalMutex = CreateMutex(NULL, FALSE, NULL); 578 579 mState = condState; 580} 581 582/* 583 * Destructor. Free Windows resources as well as our allocated storage. 584 */ 585Condition::~Condition() 586{ 587 WinCondition* condState = (WinCondition*) mState; 588 if (condState != NULL) { 589 CloseHandle(condState->sema); 590 CloseHandle(condState->waitersDone); 591 delete condState; 592 } 593} 594 595 596status_t Condition::wait(Mutex& mutex) 597{ 598 WinCondition* condState = (WinCondition*) mState; 599 HANDLE hMutex = (HANDLE) mutex.mState; 600 601 return ((WinCondition*)mState)->wait(condState, hMutex, NULL); 602} 603 604status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime) 605{ 606 WinCondition* condState = (WinCondition*) mState; 607 HANDLE hMutex = (HANDLE) mutex.mState; 608 nsecs_t absTime = systemTime()+reltime; 609 610 return ((WinCondition*)mState)->wait(condState, hMutex, &absTime); 611} 612 613/* 614 * Signal the condition variable, allowing one thread to continue. 615 */ 616void Condition::signal() 617{ 618 WinCondition* condState = (WinCondition*) mState; 619 620 // Lock the internal mutex. This ensures that we don't clash with 621 // broadcast(). 622 WaitForSingleObject(condState->internalMutex, INFINITE); 623 624 EnterCriticalSection(&condState->waitersCountLock); 625 bool haveWaiters = (condState->waitersCount > 0); 626 LeaveCriticalSection(&condState->waitersCountLock); 627 628 // If no waiters, then this is a no-op. Otherwise, knock the semaphore 629 // down a notch. 630 if (haveWaiters) 631 ReleaseSemaphore(condState->sema, 1, 0); 632 633 // Release internal mutex. 634 ReleaseMutex(condState->internalMutex); 635} 636 637/* 638 * Signal the condition variable, allowing all threads to continue. 639 * 640 * First we have to wake up all threads waiting on the semaphore, then 641 * we wait until all of the threads have actually been woken before 642 * releasing the internal mutex. This ensures that all threads are woken. 643 */ 644void Condition::broadcast() 645{ 646 WinCondition* condState = (WinCondition*) mState; 647 648 // Lock the internal mutex. This keeps the guys we're waking up 649 // from getting too far. 650 WaitForSingleObject(condState->internalMutex, INFINITE); 651 652 EnterCriticalSection(&condState->waitersCountLock); 653 bool haveWaiters = false; 654 655 if (condState->waitersCount > 0) { 656 haveWaiters = true; 657 condState->wasBroadcast = true; 658 } 659 660 if (haveWaiters) { 661 // Wake up all the waiters. 662 ReleaseSemaphore(condState->sema, condState->waitersCount, 0); 663 664 LeaveCriticalSection(&condState->waitersCountLock); 665 666 // Wait for all awakened threads to acquire the counting semaphore. 667 // The last guy who was waiting sets this. 668 WaitForSingleObject(condState->waitersDone, INFINITE); 669 670 // Reset wasBroadcast. (No crit section needed because nobody 671 // else can wake up to poke at it.) 672 condState->wasBroadcast = 0; 673 } else { 674 // nothing to do 675 LeaveCriticalSection(&condState->waitersCountLock); 676 } 677 678 // Release internal mutex. 679 ReleaseMutex(condState->internalMutex); 680} 681 682#else 683#error "condition variables not supported on this platform" 684#endif 685 686// ---------------------------------------------------------------------------- 687 688/* 689 * This is our thread object! 690 */ 691 692Thread::Thread(bool canCallJava) 693 : mCanCallJava(canCallJava), 694 mThread(thread_id_t(-1)), 695 mLock("Thread::mLock"), 696 mStatus(NO_ERROR), 697 mExitPending(false), mRunning(false) 698#ifdef HAVE_ANDROID_OS 699 , mTid(-1) 700#endif 701{ 702} 703 704Thread::~Thread() 705{ 706} 707 708status_t Thread::readyToRun() 709{ 710 return NO_ERROR; 711} 712 713status_t Thread::run(const char* name, int32_t priority, size_t stack) 714{ 715 Mutex::Autolock _l(mLock); 716 717 if (mRunning) { 718 // thread already started 719 return INVALID_OPERATION; 720 } 721 722 // reset status and exitPending to their default value, so we can 723 // try again after an error happened (either below, or in readyToRun()) 724 mStatus = NO_ERROR; 725 mExitPending = false; 726 mThread = thread_id_t(-1); 727 728 // hold a strong reference on ourself 729 mHoldSelf = this; 730 731 mRunning = true; 732 733 bool res; 734 if (mCanCallJava) { 735 res = createThreadEtc(_threadLoop, 736 this, name, priority, stack, &mThread); 737 } else { 738 res = androidCreateRawThreadEtc(_threadLoop, 739 this, name, priority, stack, &mThread); 740 } 741 742 if (res == false) { 743 mStatus = UNKNOWN_ERROR; // something happened! 744 mRunning = false; 745 mThread = thread_id_t(-1); 746 mHoldSelf.clear(); // "this" may have gone away after this. 747 748 return UNKNOWN_ERROR; 749 } 750 751 // Do not refer to mStatus here: The thread is already running (may, in fact 752 // already have exited with a valid mStatus result). The NO_ERROR indication 753 // here merely indicates successfully starting the thread and does not 754 // imply successful termination/execution. 755 return NO_ERROR; 756 757 // Exiting scope of mLock is a memory barrier and allows new thread to run 758} 759 760int Thread::_threadLoop(void* user) 761{ 762 Thread* const self = static_cast<Thread*>(user); 763 764 sp<Thread> strong(self->mHoldSelf); 765 wp<Thread> weak(strong); 766 self->mHoldSelf.clear(); 767 768#ifdef HAVE_ANDROID_OS 769 // this is very useful for debugging with gdb 770 self->mTid = gettid(); 771#endif 772 773 bool first = true; 774 775 do { 776 bool result; 777 if (first) { 778 first = false; 779 self->mStatus = self->readyToRun(); 780 result = (self->mStatus == NO_ERROR); 781 782 if (result && !self->exitPending()) { 783 // Binder threads (and maybe others) rely on threadLoop 784 // running at least once after a successful ::readyToRun() 785 // (unless, of course, the thread has already been asked to exit 786 // at that point). 787 // This is because threads are essentially used like this: 788 // (new ThreadSubclass())->run(); 789 // The caller therefore does not retain a strong reference to 790 // the thread and the thread would simply disappear after the 791 // successful ::readyToRun() call instead of entering the 792 // threadLoop at least once. 793 result = self->threadLoop(); 794 } 795 } else { 796 result = self->threadLoop(); 797 } 798 799 // establish a scope for mLock 800 { 801 Mutex::Autolock _l(self->mLock); 802 if (result == false || self->mExitPending) { 803 self->mExitPending = true; 804 self->mRunning = false; 805 // clear thread ID so that requestExitAndWait() does not exit if 806 // called by a new thread using the same thread ID as this one. 807 self->mThread = thread_id_t(-1); 808 // note that interested observers blocked in requestExitAndWait are 809 // awoken by broadcast, but blocked on mLock until break exits scope 810 self->mThreadExitedCondition.broadcast(); 811 break; 812 } 813 } 814 815 // Release our strong reference, to let a chance to the thread 816 // to die a peaceful death. 817 strong.clear(); 818 // And immediately, re-acquire a strong reference for the next loop 819 strong = weak.promote(); 820 } while(strong != 0); 821 822 return 0; 823} 824 825void Thread::requestExit() 826{ 827 Mutex::Autolock _l(mLock); 828 mExitPending = true; 829} 830 831status_t Thread::requestExitAndWait() 832{ 833 Mutex::Autolock _l(mLock); 834 if (mThread == getThreadId()) { 835 ALOGW( 836 "Thread (this=%p): don't call waitForExit() from this " 837 "Thread object's thread. It's a guaranteed deadlock!", 838 this); 839 840 return WOULD_BLOCK; 841 } 842 843 mExitPending = true; 844 845 while (mRunning == true) { 846 mThreadExitedCondition.wait(mLock); 847 } 848 // This next line is probably not needed any more, but is being left for 849 // historical reference. Note that each interested party will clear flag. 850 mExitPending = false; 851 852 return mStatus; 853} 854 855status_t Thread::join() 856{ 857 Mutex::Autolock _l(mLock); 858 if (mThread == getThreadId()) { 859 ALOGW( 860 "Thread (this=%p): don't call join() from this " 861 "Thread object's thread. It's a guaranteed deadlock!", 862 this); 863 864 return WOULD_BLOCK; 865 } 866 867 while (mRunning == true) { 868 mThreadExitedCondition.wait(mLock); 869 } 870 871 return mStatus; 872} 873 874#ifdef HAVE_ANDROID_OS 875pid_t Thread::getTid() const 876{ 877 // mTid is not defined until the child initializes it, and the caller may need it earlier 878 Mutex::Autolock _l(mLock); 879 pid_t tid; 880 if (mRunning) { 881 pthread_t pthread = android_thread_id_t_to_pthread(mThread); 882 tid = __pthread_gettid(pthread); 883 } else { 884 ALOGW("Thread (this=%p): getTid() is undefined before run()", this); 885 tid = -1; 886 } 887 return tid; 888} 889#endif 890 891bool Thread::exitPending() const 892{ 893 Mutex::Autolock _l(mLock); 894 return mExitPending; 895} 896 897 898 899}; // namespace android 900