/*
* 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 <cutils/sched_policy.h>
#include <cutils/properties.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>
#ifdef HAVE_ANDROID_OS
# include <bionic_pthread.h>
#endif
#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 thread.
*
* We create it "detached", so it cleans up after itself.
*/
typedef void* (*android_pthread_entry)(void*);
static pthread_once_t gDoSchedulingGroupOnce = PTHREAD_ONCE_INIT;
static bool gDoSchedulingGroup = true;
static void checkDoSchedulingGroup(void) {
char buf[PROPERTY_VALUE_MAX];
int len = property_get("debug.sys.noschedgroups", buf, "");
if (len > 0) {
int temp;
if (sscanf(buf, "%d", &temp) == 1) {
gDoSchedulingGroup = temp == 0;
}
}
}
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, and name with prctl.
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);
pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
if (gDoSchedulingGroup) {
if (prio >= ANDROID_PRIORITY_BACKGROUND) {
set_sched_policy(androidGetTid(), SP_BACKGROUND);
} else if (prio > ANDROID_PRIORITY_AUDIO) {
set_sched_policy(androidGetTid(), SP_FOREGROUND);
} else {
// defaults to that of parent, or as set by requestPriority()
}
}
if (name) {
androidSetThreadName(name);
free(name);
}
return f(u);
}
};
void androidSetThreadName(const char* 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;
const 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
}
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) {
// Now that the pthread_t has a method to find the associated
// android_thread_id_t (pid) from pthread_t, it would be possible to avoid
// this trampoline in some cases as the parent could set the properties
// for the child. However, there would be a race condition because the
// child becomes ready immediately, and it doesn't work for the name.
// prctl(PR_SET_NAME) only works for self; prctl(PR_SET_THREAD_NAME) was
// proposed but not yet accepted.
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);
pthread_attr_destroy(&attr);
if (result != 0) {
ALOGE("androidCreateRawThreadEtc failed (entry=%p, res=%d, errno=%d)\n"
"(android threadPriority=%d)",
entryFunction, result, errno, threadPriority);
return 0;
}
// Note that *threadID is directly available to the parent only, as it is
// assigned after the child starts. Use memory barrier / lock if the child
// or other threads also need access.
if (threadId != NULL) {
*threadId = (android_thread_id_t)thread; // XXX: this is not portable
}
return 1;
}
#ifdef HAVE_ANDROID_OS
static pthread_t android_thread_id_t_to_pthread(android_thread_id_t thread)
{
return (pthread_t) thread;
}
#endif
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;
ALOG(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
{
ALOG(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;
}
pid_t androidGetTid()
{
#ifdef HAVE_GETTID
return gettid();
#else
return getpid();
#endif
}
#ifdef HAVE_ANDROID_OS
int androidSetThreadPriority(pid_t tid, int pri)
{
int rc = 0;
#if defined(HAVE_PTHREADS)
int lasterr = 0;
pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
if (gDoSchedulingGroup) {
// set_sched_policy does not support tid == 0
int policy_tid;
if (tid == 0) {
policy_tid = androidGetTid();
} else {
policy_tid = tid;
}
if (pri >= ANDROID_PRIORITY_BACKGROUND) {
rc = set_sched_policy(policy_tid, SP_BACKGROUND);
} else if (getpriority(PRIO_PROCESS, tid) >= ANDROID_PRIORITY_BACKGROUND) {
rc = set_sched_policy(policy_tid, SP_FOREGROUND);
}
}
if (rc) {
lasterr = errno;
}
if (setpriority(PRIO_PROCESS, tid, pri) < 0) {
rc = INVALID_OPERATION;
} else {
errno = lasterr;
}
#endif
return rc;
}
int androidGetThreadPriority(pid_t tid) {
#if defined(HAVE_PTHREADS)
return getpriority(PRIO_PROCESS, tid);
#else
return ANDROID_PRIORITY_NORMAL;
#endif
}
#endif
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))
ALOG(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)
ALOG(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)
#ifdef HAVE_ANDROID_OS
, mTid(-1)
#endif
{
}
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;
// Exiting scope of mLock is a memory barrier and allows new thread to run
}
int Thread::_threadLoop(void* user)
{
Thread* const self = static_cast<Thread*>(user);
sp<Thread> strong(self->mHoldSelf);
wp<Thread> weak(strong);
self->mHoldSelf.clear();
#ifdef 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->exitPending()) {
// 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();
}
// establish a scope for mLock
{
Mutex::Autolock _l(self->mLock);
if (result == false || self->mExitPending) {
self->mExitPending = true;
self->mRunning = false;
// clear thread ID so that requestExitAndWait() does not exit if
// called by a new thread using the same thread ID as this one.
self->mThread = thread_id_t(-1);
// note that interested observers blocked in requestExitAndWait are
// awoken by broadcast, but blocked on mLock until break exits scope
self->mThreadExitedCondition.broadcast();
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()
{
Mutex::Autolock _l(mLock);
mExitPending = true;
}
status_t Thread::requestExitAndWait()
{
Mutex::Autolock _l(mLock);
if (mThread == getThreadId()) {
ALOGW(
"Thread (this=%p): don't call waitForExit() from this "
"Thread object's thread. It's a guaranteed deadlock!",
this);
return WOULD_BLOCK;
}
mExitPending = true;
while (mRunning == true) {
mThreadExitedCondition.wait(mLock);
}
// This next line is probably not needed any more, but is being left for
// historical reference. Note that each interested party will clear flag.
mExitPending = false;
return mStatus;
}
status_t Thread::join()
{
Mutex::Autolock _l(mLock);
if (mThread == getThreadId()) {
ALOGW(
"Thread (this=%p): don't call join() from this "
"Thread object's thread. It's a guaranteed deadlock!",
this);
return WOULD_BLOCK;
}
while (mRunning == true) {
mThreadExitedCondition.wait(mLock);
}
return mStatus;
}
bool Thread::isRunning() const {
Mutex::Autolock _l(mLock);
return mRunning;
}
#ifdef HAVE_ANDROID_OS
pid_t Thread::getTid() const
{
// mTid is not defined until the child initializes it, and the caller may need it earlier
Mutex::Autolock _l(mLock);
pid_t tid;
if (mRunning) {
pthread_t pthread = android_thread_id_t_to_pthread(mThread);
tid = __pthread_gettid(pthread);
} else {
ALOGW("Thread (this=%p): getTid() is undefined before run()", this);
tid = -1;
}
return tid;
}
#endif
bool Thread::exitPending() const
{
Mutex::Autolock _l(mLock);
return mExitPending;
}
}; // namespace android