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/*
* Copyright (C) 2007, 2009, 2015 Apple Inc. All rights reserved.
* Copyright (C) 2007 Justin Haygood <jhaygood@reaktix.com>
* Copyright (C) 2011 Research In Motion Limited. All rights reserved.
* Copyright (C) 2017 Yusuke Suzuki <utatane.tea@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include <wtf/Threading.h>
#if USE(PTHREADS)
#include <errno.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/StdLibExtras.h>
#include <wtf/ThreadingPrimitives.h>
#include <wtf/WordLock.h>
#if OS(LINUX)
#include <sys/prctl.h>
#endif
#if !COMPILER(MSVC)
#include <limits.h>
#include <sched.h>
#include <sys/time.h>
#endif
#if !OS(DARWIN) && OS(UNIX)
#include <semaphore.h>
#include <sys/mman.h>
#include <unistd.h>
#include <pthread.h>
#if HAVE(PTHREAD_NP_H)
#include <pthread_np.h>
#endif
#endif
namespace WTF {
static Lock globalSuspendLock;
Thread::~Thread()
{
}
#if !OS(DARWIN)
class Semaphore final {
WTF_MAKE_NONCOPYABLE(Semaphore);
WTF_MAKE_FAST_ALLOCATED;
public:
explicit Semaphore(unsigned initialValue)
{
int sharedBetweenProcesses = 0;
sem_init(&m_platformSemaphore, sharedBetweenProcesses, initialValue);
}
~Semaphore()
{
sem_destroy(&m_platformSemaphore);
}
void wait()
{
sem_wait(&m_platformSemaphore);
}
void post()
{
sem_post(&m_platformSemaphore);
}
private:
sem_t m_platformSemaphore;
};
static LazyNeverDestroyed<Semaphore> globalSemaphoreForSuspendResume;
static std::atomic<Thread*> targetThread { nullptr };
void Thread::signalHandlerSuspendResume(int, siginfo_t*, void* ucontext)
{
// Touching a global variable atomic types from signal handlers is allowed.
Thread* thread = targetThread.load();
if (thread->m_suspendCount) {
// This is signal handler invocation that is intended to be used to resume sigsuspend.
// So this handler invocation itself should not process.
//
// When signal comes, first, the system calls signal handler. And later, sigsuspend will be resumed. Signal handler invocation always precedes.
// So, the problem never happens that suspended.store(true, ...) will be executed before the handler is called.
// http://pubs.opengroup.org/onlinepubs/009695399/functions/sigsuspend.html
return;
}
void* approximateStackPointer = currentStackPointer();
if (!thread->m_stack.contains(approximateStackPointer)) {
// This happens if we use an alternative signal stack.
// 1. A user-defined signal handler is invoked with an alternative signal stack.
// 2. In the middle of the execution of the handler, we attempt to suspend the target thread.
// 3. A nested signal handler is executed.
// 4. The stack pointer saved in the machine context will be pointing to the alternative signal stack.
// In this case, we back off the suspension and retry a bit later.
thread->m_platformRegisters = nullptr;
globalSemaphoreForSuspendResume->post();
return;
}
#if HAVE(MACHINE_CONTEXT)
ucontext_t* userContext = static_cast<ucontext_t*>(ucontext);
thread->m_platformRegisters = &registersFromUContext(userContext);
#else
UNUSED_PARAM(ucontext);
PlatformRegisters platformRegisters { approximateStackPointer };
thread->m_platformRegisters = &platformRegisters;
#endif
// Allow suspend caller to see that this thread is suspended.
// sem_post is async-signal-safe function. It means that we can call this from a signal handler.
// http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html#tag_02_04_03
//
// And sem_post emits memory barrier that ensures that PlatformRegisters are correctly saved.
// http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_11
globalSemaphoreForSuspendResume->post();
// Reaching here, SigThreadSuspendResume is blocked in this handler (this is configured by sigaction's sa_mask).
// So before calling sigsuspend, SigThreadSuspendResume to this thread is deferred. This ensures that the handler is not executed recursively.
sigset_t blockedSignalSet;
sigfillset(&blockedSignalSet);
sigdelset(&blockedSignalSet, SigThreadSuspendResume);
sigsuspend(&blockedSignalSet);
thread->m_platformRegisters = nullptr;
// Allow resume caller to see that this thread is resumed.
globalSemaphoreForSuspendResume->post();
}
#endif // !OS(DARWIN)
void Thread::initializePlatformThreading()
{
#if !OS(DARWIN)
globalSemaphoreForSuspendResume.construct(0);
// Signal handlers are process global configuration.
// Intentionally block SigThreadSuspendResume in the handler.
// SigThreadSuspendResume will be allowed in the handler by sigsuspend.
struct sigaction action;
sigemptyset(&action.sa_mask);
sigaddset(&action.sa_mask, SigThreadSuspendResume);
action.sa_sigaction = &signalHandlerSuspendResume;
action.sa_flags = SA_RESTART | SA_SIGINFO;
sigaction(SigThreadSuspendResume, &action, 0);
#endif
}
void Thread::initializeCurrentThreadEvenIfNonWTFCreated()
{
#if !OS(DARWIN)
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, SigThreadSuspendResume);
pthread_sigmask(SIG_UNBLOCK, &mask, 0);
#endif
}
static void* wtfThreadEntryPoint(void* context)
{
Thread::entryPoint(reinterpret_cast<Thread::NewThreadContext*>(context));
return nullptr;
}
bool Thread::establishHandle(NewThreadContext* context, Optional<size_t> stackSize)
{
pthread_t threadHandle;
pthread_attr_t attr;
pthread_attr_init(&attr);
#if HAVE(QOS_CLASSES)
pthread_attr_set_qos_class_np(&attr, adjustedQOSClass(QOS_CLASS_USER_INITIATED), 0);
#endif
if (stackSize)
pthread_attr_setstacksize(&attr, stackSize.value());
int error = pthread_create(&threadHandle, &attr, wtfThreadEntryPoint, context);
pthread_attr_destroy(&attr);
if (error) {
LOG_ERROR("Failed to create pthread at entry point %p with context %p", wtfThreadEntryPoint, context);
return false;
}
establishPlatformSpecificHandle(threadHandle);
return true;
}
void Thread::initializeCurrentThreadInternal(const char* threadName)
{
#if HAVE(PTHREAD_SETNAME_NP)
pthread_setname_np(normalizeThreadName(threadName));
#elif OS(LINUX)
prctl(PR_SET_NAME, normalizeThreadName(threadName));
#else
UNUSED_PARAM(threadName);
#endif
initializeCurrentThreadEvenIfNonWTFCreated();
}
void Thread::changePriority(int delta)
{
#if HAVE(PTHREAD_SETSCHEDPARAM)
auto locker = holdLock(m_mutex);
int policy;
struct sched_param param;
if (pthread_getschedparam(m_handle, &policy, &param))
return;
param.sched_priority += delta;
pthread_setschedparam(m_handle, policy, &param);
#endif
}
int Thread::waitForCompletion()
{
pthread_t handle;
{
auto locker = holdLock(m_mutex);
handle = m_handle;
}
int joinResult = pthread_join(handle, 0);
if (joinResult == EDEADLK)
LOG_ERROR("Thread %p was found to be deadlocked trying to quit", this);
else if (joinResult)
LOG_ERROR("Thread %p was unable to be joined.\n", this);
auto locker = holdLock(m_mutex);
ASSERT(joinableState() == Joinable);
// If the thread has already exited, then do nothing. If the thread hasn't exited yet, then just signal that we've already joined on it.
// In both cases, Thread::destructTLS() will take care of destroying Thread.
if (!hasExited())
didJoin();
return joinResult;
}
void Thread::detach()
{
auto locker = holdLock(m_mutex);
int detachResult = pthread_detach(m_handle);
if (detachResult)
LOG_ERROR("Thread %p was unable to be detached\n", this);
if (!hasExited())
didBecomeDetached();
}
Thread& Thread::initializeCurrentTLS()
{
// Not a WTF-created thread, Thread is not established yet.
Ref<Thread> thread = adoptRef(*new Thread());
thread->establishPlatformSpecificHandle(pthread_self());
thread->initializeInThread();
initializeCurrentThreadEvenIfNonWTFCreated();
return initializeTLS(WTFMove(thread));
}
bool Thread::signal(int signalNumber)
{
auto locker = holdLock(m_mutex);
if (hasExited())
return false;
int errNo = pthread_kill(m_handle, signalNumber);
return !errNo; // A 0 errNo means success.
}
auto Thread::suspend() -> Expected<void, PlatformSuspendError>
{
RELEASE_ASSERT_WITH_MESSAGE(this != &Thread::current(), "We do not support suspending the current thread itself.");
// During suspend, suspend or resume should not be executed from the other threads.
// We use global lock instead of per thread lock.
// Consider the following case, there are threads A and B.
// And A attempt to suspend B and B attempt to suspend A.
// A and B send signals. And later, signals are delivered to A and B.
// In that case, both will be suspended.
//
// And it is important to use a global lock to suspend and resume. Let's consider using per-thread lock.
// Your issuing thread (A) attempts to suspend the target thread (B). Then, you will suspend the thread (C) additionally.
// This case frequently happens if you stop threads to perform stack scanning. But thread (B) may hold the lock of thread (C).
// In that case, dead lock happens. Using global lock here avoids this dead lock.
LockHolder locker(globalSuspendLock);
#if OS(DARWIN)
kern_return_t result = thread_suspend(m_platformThread);
if (result != KERN_SUCCESS)
return makeUnexpected(result);
return { };
#else
if (!m_suspendCount) {
// Ideally, we would like to use pthread_sigqueue. It allows us to pass the argument to the signal handler.
// But it can be used in a few platforms, like Linux.
// Instead, we use Thread* stored in a global variable to pass it to the signal handler.
targetThread.store(this);
while (true) {
int result = pthread_kill(m_handle, SigThreadSuspendResume);
if (result)
return makeUnexpected(result);
globalSemaphoreForSuspendResume->wait();
if (m_platformRegisters)
break;
// Because of an alternative signal stack, we failed to suspend this thread.
// Retry suspension again after yielding.
Thread::yield();
}
}
++m_suspendCount;
return { };
#endif
}
void Thread::resume()
{
// During resume, suspend or resume should not be executed from the other threads.
LockHolder locker(globalSuspendLock);
#if OS(DARWIN)
thread_resume(m_platformThread);
#else
if (m_suspendCount == 1) {
// When allowing SigThreadSuspendResume interrupt in the signal handler by sigsuspend and SigThreadSuspendResume is actually issued,
// the signal handler itself will be called once again.
// There are several ways to distinguish the handler invocation for suspend and resume.
// 1. Use different signal numbers. And check the signal number in the handler.
// 2. Use some arguments to distinguish suspend and resume in the handler. If pthread_sigqueue can be used, we can take this.
// 3. Use thread's flag.
// In this implementaiton, we take (3). m_suspendCount is used to distinguish it.
targetThread.store(this);
if (pthread_kill(m_handle, SigThreadSuspendResume) == ESRCH)
return;
globalSemaphoreForSuspendResume->wait();
}
--m_suspendCount;
#endif
}
#if OS(DARWIN)
struct ThreadStateMetadata {
WTF_MAKE_STRUCT_FAST_ALLOCATED;
unsigned userCount;
thread_state_flavor_t flavor;
};
static ThreadStateMetadata threadStateMetadata()
{
#if CPU(X86)
unsigned userCount = sizeof(PlatformRegisters) / sizeof(int);
thread_state_flavor_t flavor = i386_THREAD_STATE;
#elif CPU(X86_64)
unsigned userCount = x86_THREAD_STATE64_COUNT;
thread_state_flavor_t flavor = x86_THREAD_STATE64;
#elif CPU(PPC)
unsigned userCount = PPC_THREAD_STATE_COUNT;
thread_state_flavor_t flavor = PPC_THREAD_STATE;
#elif CPU(PPC64)
unsigned userCount = PPC_THREAD_STATE64_COUNT;
thread_state_flavor_t flavor = PPC_THREAD_STATE64;
#elif CPU(ARM)
unsigned userCount = ARM_THREAD_STATE_COUNT;
thread_state_flavor_t flavor = ARM_THREAD_STATE;
#elif CPU(ARM64)
unsigned userCount = ARM_THREAD_STATE64_COUNT;
thread_state_flavor_t flavor = ARM_THREAD_STATE64;
#else
#error Unknown Architecture
#endif
return ThreadStateMetadata { userCount, flavor };
}
#endif // OS(DARWIN)
size_t Thread::getRegisters(PlatformRegisters& registers)
{
LockHolder locker(globalSuspendLock);
#if OS(DARWIN)
auto metadata = threadStateMetadata();
kern_return_t result = thread_get_state(m_platformThread, metadata.flavor, (thread_state_t)&registers, &metadata.userCount);
if (result != KERN_SUCCESS) {
WTFReportFatalError(__FILE__, __LINE__, WTF_PRETTY_FUNCTION, "JavaScript garbage collection failed because thread_get_state returned an error (%d). This is probably the result of running inside Rosetta, which is not supported.", result);
CRASH();
}
return metadata.userCount * sizeof(uintptr_t);
#else
ASSERT_WITH_MESSAGE(m_suspendCount, "We can get registers only if the thread is suspended.");
ASSERT(m_platformRegisters);
registers = *m_platformRegisters;
return sizeof(PlatformRegisters);
#endif
}
void Thread::establishPlatformSpecificHandle(pthread_t handle)
{
auto locker = holdLock(m_mutex);
m_handle = handle;
#if OS(DARWIN)
m_platformThread = pthread_mach_thread_np(handle);
#endif
}
#if !HAVE(FAST_TLS)
void Thread::initializeTLSKey()
{
threadSpecificKeyCreate(&s_key, destructTLS);
}
#endif
Thread& Thread::initializeTLS(Ref<Thread>&& thread)
{
// We leak the ref to keep the Thread alive while it is held in TLS. destructTLS will deref it later at thread destruction time.
auto& threadInTLS = thread.leakRef();
#if !HAVE(FAST_TLS)
ASSERT(s_key != InvalidThreadSpecificKey);
threadSpecificSet(s_key, &threadInTLS);
#else
_pthread_setspecific_direct(WTF_THREAD_DATA_KEY, &threadInTLS);
pthread_key_init_np(WTF_THREAD_DATA_KEY, &destructTLS);
#endif
return threadInTLS;
}
void Thread::destructTLS(void* data)
{
Thread* thread = static_cast<Thread*>(data);
ASSERT(thread);
if (thread->m_isDestroyedOnce) {
thread->didExit();
thread->deref();
return;
}
thread->m_isDestroyedOnce = true;
// Re-setting the value for key causes another destructTLS() call after all other thread-specific destructors were called.
#if !HAVE(FAST_TLS)
ASSERT(s_key != InvalidThreadSpecificKey);
threadSpecificSet(s_key, thread);
#else
_pthread_setspecific_direct(WTF_THREAD_DATA_KEY, thread);
pthread_key_init_np(WTF_THREAD_DATA_KEY, &destructTLS);
#endif
}
Mutex::~Mutex()
{
int result = pthread_mutex_destroy(&m_mutex);
ASSERT_UNUSED(result, !result);
}
void Mutex::lock()
{
int result = pthread_mutex_lock(&m_mutex);
ASSERT_UNUSED(result, !result);
}
bool Mutex::tryLock()
{
int result = pthread_mutex_trylock(&m_mutex);
if (result == 0)
return true;
if (result == EBUSY)
return false;
ASSERT_NOT_REACHED();
return false;
}
void Mutex::unlock()
{
int result = pthread_mutex_unlock(&m_mutex);
ASSERT_UNUSED(result, !result);
}
ThreadCondition::~ThreadCondition()
{
pthread_cond_destroy(&m_condition);
}
void ThreadCondition::wait(Mutex& mutex)
{
int result = pthread_cond_wait(&m_condition, &mutex.impl());
ASSERT_UNUSED(result, !result);
}
bool ThreadCondition::timedWait(Mutex& mutex, WallTime absoluteTime)
{
if (absoluteTime < WallTime::now())
return false;
if (absoluteTime > WallTime::fromRawSeconds(INT_MAX)) {
wait(mutex);
return true;
}
double rawSeconds = absoluteTime.secondsSinceEpoch().value();
int timeSeconds = static_cast<int>(rawSeconds);
int timeNanoseconds = static_cast<int>((rawSeconds - timeSeconds) * 1E9);
timespec targetTime;
targetTime.tv_sec = timeSeconds;
targetTime.tv_nsec = timeNanoseconds;
return pthread_cond_timedwait(&m_condition, &mutex.impl(), &targetTime) == 0;
}
void ThreadCondition::signal()
{
int result = pthread_cond_signal(&m_condition);
ASSERT_UNUSED(result, !result);
}
void ThreadCondition::broadcast()
{
int result = pthread_cond_broadcast(&m_condition);
ASSERT_UNUSED(result, !result);
}
void Thread::yield()
{
sched_yield();
}
} // namespace WTF
#endif // USE(PTHREADS)