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/*
* Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/javaThreadStatus.hpp"
#include "gc/shared/barrierSet.hpp"
#include "jfr/jfrEvents.hpp"
#include "jvm.h"
#include "jvmtifiles/jvmtiEnv.hpp"
#include "logging/log.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/iterator.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/javaThread.inline.hpp"
#include "runtime/nonJavaThread.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/osThread.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/safepointMechanism.inline.hpp"
#include "runtime/thread.inline.hpp"
#include "runtime/threadSMR.inline.hpp"
#include "services/memTracker.hpp"
#include "utilities/macros.hpp"
#include "utilities/spinYield.hpp"
#if INCLUDE_JFR
#include "jfr/jfr.hpp"
#endif
#ifndef USE_LIBRARY_BASED_TLS_ONLY
// Current thread is maintained as a thread-local variable
THREAD_LOCAL Thread* Thread::_thr_current = NULL;
#endif
// ======= Thread ========
void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
return throw_excpt ? AllocateHeap(size, flags, CURRENT_PC)
: AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
}
void Thread::operator delete(void* p) {
FreeHeap(p);
}
// Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
// JavaThread
DEBUG_ONLY(Thread* Thread::_starting_thread = NULL;)
Thread::Thread() {
DEBUG_ONLY(_run_state = PRE_CALL_RUN;)
// stack and get_thread
set_stack_base(NULL);
set_stack_size(0);
set_lgrp_id(-1);
DEBUG_ONLY(clear_suspendible_thread();)
// allocated data structures
set_osthread(NULL);
set_resource_area(new (mtThread)ResourceArea());
DEBUG_ONLY(_current_resource_mark = NULL;)
set_handle_area(new (mtThread) HandleArea(NULL));
set_metadata_handles(new (mtClass) GrowableArray<Metadata*>(30, mtClass));
set_last_handle_mark(NULL);
DEBUG_ONLY(_missed_ic_stub_refill_verifier = NULL);
// Initial value of zero ==> never claimed.
_threads_do_token = 0;
_threads_hazard_ptr = NULL;
_threads_list_ptr = NULL;
_nested_threads_hazard_ptr_cnt = 0;
_rcu_counter = 0;
// the handle mark links itself to last_handle_mark
new HandleMark(this);
// plain initialization
debug_only(_owned_locks = NULL;)
NOT_PRODUCT(_skip_gcalot = false;)
_jvmti_env_iteration_count = 0;
set_allocated_bytes(0);
_current_pending_raw_monitor = NULL;
// thread-specific hashCode stream generator state - Marsaglia shift-xor form
_hashStateX = os::random();
_hashStateY = 842502087;
_hashStateZ = 0x8767; // (int)(3579807591LL & 0xffff) ;
_hashStateW = 273326509;
// Many of the following fields are effectively final - immutable
// Note that nascent threads can't use the Native Monitor-Mutex
// construct until the _MutexEvent is initialized ...
// CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
// we might instead use a stack of ParkEvents that we could provision on-demand.
// The stack would act as a cache to avoid calls to ParkEvent::Allocate()
// and ::Release()
_ParkEvent = ParkEvent::Allocate(this);
#ifdef CHECK_UNHANDLED_OOPS
if (CheckUnhandledOops) {
_unhandled_oops = new UnhandledOops(this);
}
#endif // CHECK_UNHANDLED_OOPS
// Notify the barrier set that a thread is being created. The initial
// thread is created before the barrier set is available. The call to
// BarrierSet::on_thread_create() for this thread is therefore deferred
// to BarrierSet::set_barrier_set().
BarrierSet* const barrier_set = BarrierSet::barrier_set();
if (barrier_set != NULL) {
barrier_set->on_thread_create(this);
} else {
// Only the main thread should be created before the barrier set
// and that happens just before Thread::current is set. No other thread
// can attach as the VM is not created yet, so they can't execute this code.
// If the main thread creates other threads before the barrier set that is an error.
assert(Thread::current_or_null() == NULL, "creating thread before barrier set");
}
MACOS_AARCH64_ONLY(DEBUG_ONLY(_wx_init = false));
}
void Thread::initialize_tlab() {
if (UseTLAB) {
tlab().initialize();
}
}
void Thread::initialize_thread_current() {
#ifndef USE_LIBRARY_BASED_TLS_ONLY
assert(_thr_current == NULL, "Thread::current already initialized");
_thr_current = this;
#endif
assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
ThreadLocalStorage::set_thread(this);
assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
}
void Thread::clear_thread_current() {
assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
#ifndef USE_LIBRARY_BASED_TLS_ONLY
_thr_current = NULL;
#endif
ThreadLocalStorage::set_thread(NULL);
}
void Thread::record_stack_base_and_size() {
// Note: at this point, Thread object is not yet initialized. Do not rely on
// any members being initialized. Do not rely on Thread::current() being set.
// If possible, refrain from doing anything which may crash or assert since
// quite probably those crash dumps will be useless.
set_stack_base(os::current_stack_base());
set_stack_size(os::current_stack_size());
// Set stack limits after thread is initialized.
if (is_Java_thread()) {
JavaThread::cast(this)->stack_overflow_state()->initialize(stack_base(), stack_end());
}
}
void Thread::register_thread_stack_with_NMT() {
MemTracker::record_thread_stack(stack_end(), stack_size());
}
void Thread::unregister_thread_stack_with_NMT() {
MemTracker::release_thread_stack(stack_end(), stack_size());
}
void Thread::call_run() {
DEBUG_ONLY(_run_state = CALL_RUN;)
// At this point, Thread object should be fully initialized and
// Thread::current() should be set.
assert(Thread::current_or_null() != NULL, "current thread is unset");
assert(Thread::current_or_null() == this, "current thread is wrong");
// Perform common initialization actions
MACOS_AARCH64_ONLY(this->init_wx());
register_thread_stack_with_NMT();
JFR_ONLY(Jfr::on_thread_start(this);)
log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
os::current_thread_id(), p2i(stack_end()),
p2i(stack_base()), stack_size()/1024);
// Perform <ChildClass> initialization actions
DEBUG_ONLY(_run_state = PRE_RUN;)
this->pre_run();
// Invoke <ChildClass>::run()
DEBUG_ONLY(_run_state = RUN;)
this->run();
// Returned from <ChildClass>::run(). Thread finished.
// Perform common tear-down actions
assert(Thread::current_or_null() != NULL, "current thread is unset");
assert(Thread::current_or_null() == this, "current thread is wrong");
// Perform <ChildClass> tear-down actions
DEBUG_ONLY(_run_state = POST_RUN;)
this->post_run();
// Note: at this point the thread object may already have deleted itself,
// so from here on do not dereference *this*. Not all thread types currently
// delete themselves when they terminate. But no thread should ever be deleted
// asynchronously with respect to its termination - that is what _run_state can
// be used to check.
assert(Thread::current_or_null() == NULL, "current thread still present");
}
Thread::~Thread() {
// Attached threads will remain in PRE_CALL_RUN, as will threads that don't actually
// get started due to errors etc. Any active thread should at least reach post_run
// before it is deleted (usually in post_run()).
assert(_run_state == PRE_CALL_RUN ||
_run_state == POST_RUN, "Active Thread deleted before post_run(): "
"_run_state=%d", (int)_run_state);
// Notify the barrier set that a thread is being destroyed. Note that a barrier
// set might not be available if we encountered errors during bootstrapping.
BarrierSet* const barrier_set = BarrierSet::barrier_set();
if (barrier_set != NULL) {
barrier_set->on_thread_destroy(this);
}
// deallocate data structures
delete resource_area();
// since the handle marks are using the handle area, we have to deallocated the root
// handle mark before deallocating the thread's handle area,
assert(last_handle_mark() != NULL, "check we have an element");
delete last_handle_mark();
assert(last_handle_mark() == NULL, "check we have reached the end");
ParkEvent::Release(_ParkEvent);
// Set to NULL as a termination indicator for has_terminated().
Atomic::store(&_ParkEvent, (ParkEvent*)NULL);
delete handle_area();
delete metadata_handles();
// osthread() can be NULL, if creation of thread failed.
if (osthread() != NULL) os::free_thread(osthread());
// Clear Thread::current if thread is deleting itself and it has not
// already been done. This must be done before the memory is deallocated.
// Needed to ensure JNI correctly detects non-attached threads.
if (this == Thread::current_or_null()) {
Thread::clear_thread_current();
}
CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
}
#ifdef ASSERT
// A JavaThread is considered dangling if it not handshake-safe with respect to
// the current thread, it is not on a ThreadsList, or not at safepoint.
void Thread::check_for_dangling_thread_pointer(Thread *thread) {
assert(!thread->is_Java_thread() ||
JavaThread::cast(thread)->is_handshake_safe_for(Thread::current()) ||
!JavaThread::cast(thread)->on_thread_list() ||
SafepointSynchronize::is_at_safepoint() ||
ThreadsSMRSupport::is_a_protected_JavaThread_with_lock(JavaThread::cast(thread)),
"possibility of dangling Thread pointer");
}
#endif
// Is the target JavaThread protected by the calling Thread or by some other
// mechanism?
//
bool Thread::is_JavaThread_protected(const JavaThread* target) {
Thread* current_thread = Thread::current();
// Do the simplest check first:
if (SafepointSynchronize::is_at_safepoint()) {
// The target is protected since JavaThreads cannot exit
// while we're at a safepoint.
return true;
}
// If the target hasn't been started yet then it is trivially
// "protected". We assume the caller is the thread that will do
// the starting.
if (target->osthread() == NULL || target->osthread()->get_state() <= INITIALIZED) {
return true;
}
// Now make the simple checks based on who the caller is:
if (current_thread == target || Threads_lock->owner() == current_thread) {
// Target JavaThread is self or calling thread owns the Threads_lock.
// Second check is the same as Threads_lock->owner_is_self(),
// but we already have the current thread so check directly.
return true;
}
// Check the ThreadsLists associated with the calling thread (if any)
// to see if one of them protects the target JavaThread:
if (is_JavaThread_protected_by_TLH(target)) {
return true;
}
// Use this debug code with -XX:+UseNewCode to diagnose locations that
// are missing a ThreadsListHandle or other protection mechanism:
// guarantee(!UseNewCode, "current_thread=" INTPTR_FORMAT " is not protecting target="
// INTPTR_FORMAT, p2i(current_thread), p2i(target));
// Note: Since 'target' isn't protected by a TLH, the call to
// target->is_handshake_safe_for() may crash, but we have debug bits so
// we'll be able to figure out what protection mechanism is missing.
assert(target->is_handshake_safe_for(current_thread), "JavaThread=" INTPTR_FORMAT
" is not protected and not handshake safe.", p2i(target));
// The target JavaThread is not protected so it is not safe to query:
return false;
}
// Is the target JavaThread protected by a ThreadsListHandle (TLH) associated
// with the calling Thread?
//
bool Thread::is_JavaThread_protected_by_TLH(const JavaThread* target) {
Thread* current_thread = Thread::current();
// Check the ThreadsLists associated with the calling thread (if any)
// to see if one of them protects the target JavaThread:
for (SafeThreadsListPtr* stlp = current_thread->_threads_list_ptr;
stlp != NULL; stlp = stlp->previous()) {
if (stlp->list()->includes(target)) {
// The target JavaThread is protected by this ThreadsList:
return true;
}
}
// The target JavaThread is not protected by a TLH so it is not safe to query:
return false;
}
void Thread::set_priority(Thread* thread, ThreadPriority priority) {
debug_only(check_for_dangling_thread_pointer(thread);)
// Can return an error!
(void)os::set_priority(thread, priority);
}
void Thread::start(Thread* thread) {
// Start is different from resume in that its safety is guaranteed by context or
// being called from a Java method synchronized on the Thread object.
if (thread->is_Java_thread()) {
// Initialize the thread state to RUNNABLE before starting this thread.
// Can not set it after the thread started because we do not know the
// exact thread state at that time. It could be in MONITOR_WAIT or
// in SLEEPING or some other state.
java_lang_Thread::set_thread_status(JavaThread::cast(thread)->threadObj(),
JavaThreadStatus::RUNNABLE);
}
os::start_thread(thread);
}
// GC Support
bool Thread::claim_par_threads_do(uintx claim_token) {
uintx token = _threads_do_token;
if (token != claim_token) {
uintx res = Atomic::cmpxchg(&_threads_do_token, token, claim_token);
if (res == token) {
return true;
}
guarantee(res == claim_token, "invariant");
}
return false;
}
void Thread::oops_do_no_frames(OopClosure* f, CodeBlobClosure* cf) {
// Do oop for ThreadShadow
f->do_oop((oop*)&_pending_exception);
handle_area()->oops_do(f);
}
// If the caller is a NamedThread, then remember, in the current scope,
// the given JavaThread in its _processed_thread field.
class RememberProcessedThread: public StackObj {
NamedThread* _cur_thr;
public:
RememberProcessedThread(Thread* thread) {
Thread* self = Thread::current();
if (self->is_Named_thread()) {
_cur_thr = (NamedThread *)self;
assert(_cur_thr->processed_thread() == NULL, "nesting not supported");
_cur_thr->set_processed_thread(thread);
} else {
_cur_thr = NULL;
}
}
~RememberProcessedThread() {
if (_cur_thr) {
assert(_cur_thr->processed_thread() != NULL, "nesting not supported");
_cur_thr->set_processed_thread(NULL);
}
}
};
void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
// Record JavaThread to GC thread
RememberProcessedThread rpt(this);
oops_do_no_frames(f, cf);
oops_do_frames(f, cf);
}
void Thread::metadata_handles_do(void f(Metadata*)) {
// Only walk the Handles in Thread.
if (metadata_handles() != NULL) {
for (int i = 0; i< metadata_handles()->length(); i++) {
f(metadata_handles()->at(i));
}
}
}
void Thread::print_on(outputStream* st, bool print_extended_info) const {
// get_priority assumes osthread initialized
if (osthread() != NULL) {
int os_prio;
if (os::get_native_priority(this, &os_prio) == OS_OK) {
st->print("os_prio=%d ", os_prio);
}
st->print("cpu=%.2fms ",
os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
);
st->print("elapsed=%.2fs ",
_statistical_info.getElapsedTime() / 1000.0
);
if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
st->print("allocated=" SIZE_FORMAT "%s ",
byte_size_in_proper_unit(allocated_bytes),
proper_unit_for_byte_size(allocated_bytes)
);
st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
}
st->print("tid=" INTPTR_FORMAT " ", p2i(this));
if (!is_Java_thread() || !JavaThread::cast(this)->is_vthread_mounted()) {
osthread()->print_on(st);
}
}
ThreadsSMRSupport::print_info_on(this, st);
st->print(" ");
debug_only(if (WizardMode) print_owned_locks_on(st);)
}
void Thread::print() const { print_on(tty); }
// Thread::print_on_error() is called by fatal error handler. Don't use
// any lock or allocate memory.
void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
st->print("%s \"%s\"", type_name(), name());
OSThread* os_thr = osthread();
if (os_thr != NULL) {
if (os_thr->get_state() != ZOMBIE) {
st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
p2i(stack_end()), p2i(stack_base()));
st->print(" [id=%d]", osthread()->thread_id());
} else {
st->print(" terminated");
}
} else {
st->print(" unknown state (no osThread)");
}
ThreadsSMRSupport::print_info_on(this, st);
}
void Thread::print_value_on(outputStream* st) const {
if (is_Named_thread()) {
st->print(" \"%s\" ", name());
}
st->print(INTPTR_FORMAT, p2i(this)); // print address
}
#ifdef ASSERT
void Thread::print_owned_locks_on(outputStream* st) const {
Mutex* cur = _owned_locks;
if (cur == NULL) {
st->print(" (no locks) ");
} else {
st->print_cr(" Locks owned:");
while (cur) {
cur->print_on(st);
cur = cur->next();
}
}
}
#endif // ASSERT
// We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
// However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
// used for compilation in the future. If that change is made, the need for these methods
// should be revisited, and they should be removed if possible.
bool Thread::is_lock_owned(address adr) const {
return is_in_full_stack(adr);
}
bool Thread::set_as_starting_thread() {
assert(_starting_thread == NULL, "already initialized: "
"_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
// NOTE: this must be called inside the main thread.
DEBUG_ONLY(_starting_thread = this;)
return os::create_main_thread(JavaThread::cast(this));
}
// Ad-hoc mutual exclusion primitives: SpinLock
//
// We employ SpinLocks _only for low-contention, fixed-length
// short-duration critical sections where we're concerned
// about native mutex_t or HotSpot Mutex:: latency.
//
// TODO-FIXME: ListLock should be of type SpinLock.
// We should make this a 1st-class type, integrated into the lock
// hierarchy as leaf-locks. Critically, the SpinLock structure
// should have sufficient padding to avoid false-sharing and excessive
// cache-coherency traffic.
typedef volatile int SpinLockT;
void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
if (Atomic::cmpxchg(adr, 0, 1) == 0) {
return; // normal fast-path return
}
// Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
int ctr = 0;
int Yields = 0;
for (;;) {
while (*adr != 0) {
++ctr;
if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
if (Yields > 5) {
os::naked_short_sleep(1);
} else {
os::naked_yield();
++Yields;
}
} else {
SpinPause();
}
}
if (Atomic::cmpxchg(adr, 0, 1) == 0) return;
}
}
void Thread::SpinRelease(volatile int * adr) {
assert(*adr != 0, "invariant");
OrderAccess::fence(); // guarantee at least release consistency.
// Roach-motel semantics.
// It's safe if subsequent LDs and STs float "up" into the critical section,
// but prior LDs and STs within the critical section can't be allowed
// to reorder or float past the ST that releases the lock.
// Loads and stores in the critical section - which appear in program
// order before the store that releases the lock - must also appear
// before the store that releases the lock in memory visibility order.
// Conceptually we need a #loadstore|#storestore "release" MEMBAR before
// the ST of 0 into the lock-word which releases the lock, so fence
// more than covers this on all platforms.
*adr = 0;
}
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