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src/hotspot/share/runtime/handshake.cpp

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*** 35,89 **** #include "runtime/thread.hpp" #include "runtime/vmThread.hpp" #include "utilities/formatBuffer.hpp" #include "utilities/preserveException.hpp" - class HandshakeOperation: public StackObj { - public: - virtual void do_handshake(JavaThread* thread) = 0; - }; ! class HandshakeThreadsOperation: public HandshakeOperation { ! static Semaphore _done; HandshakeClosure* _handshake_cl; bool _executed; public: ! HandshakeThreadsOperation(HandshakeClosure* cl) : _handshake_cl(cl), _executed(false) {} void do_handshake(JavaThread* thread); ! bool thread_has_completed() { return _done.trywait(); } bool executed() const { return _executed; } const char* name() { return _handshake_cl->name(); } ! #ifdef ASSERT ! void check_state() { ! assert(!_done.trywait(), "Must be zero"); ! } ! #endif }; - Semaphore HandshakeThreadsOperation::_done(0); - class VM_Handshake: public VM_Operation { const jlong _handshake_timeout; public: bool evaluate_at_safepoint() const { return false; } protected: ! HandshakeThreadsOperation* const _op; ! VM_Handshake(HandshakeThreadsOperation* op) : _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)), _op(op) {} - void set_handshake(JavaThread* target) { - target->set_handshake_operation(_op); - } - - // This method returns true for threads completed their operation - // and true for threads canceled their operation. - // A cancellation can happen if the thread is exiting. - bool poll_for_completed_thread() { return _op->thread_has_completed(); } - bool handshake_has_timed_out(jlong start_time); static void handle_timeout(); }; bool VM_Handshake::handshake_has_timed_out(jlong start_time) { --- 35,81 ---- #include "runtime/thread.hpp" #include "runtime/vmThread.hpp" #include "utilities/formatBuffer.hpp" #include "utilities/preserveException.hpp" ! class HandshakeOperation: public StackObj { HandshakeClosure* _handshake_cl; + int32_t _pending_threads; bool _executed; + bool _is_direct; public: ! HandshakeOperation(HandshakeClosure* cl, bool is_direct = false) : ! _handshake_cl(cl), ! _pending_threads(1), ! _executed(false), ! _is_direct(is_direct) {} ! void do_handshake(JavaThread* thread); ! bool is_completed() { ! int32_t val = Atomic::load(&_pending_threads); ! assert(val >= 0, "_pending_threads=%d cannot be negative", val); ! return val == 0; ! } ! void add_target_count(int count) { Atomic::add(&_pending_threads, count, memory_order_relaxed); } bool executed() const { return _executed; } const char* name() { return _handshake_cl->name(); } ! bool is_direct() { return _is_direct; } }; class VM_Handshake: public VM_Operation { const jlong _handshake_timeout; public: bool evaluate_at_safepoint() const { return false; } protected: ! HandshakeOperation* const _op; ! VM_Handshake(HandshakeOperation* op) : _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)), _op(op) {} bool handshake_has_timed_out(jlong start_time); static void handle_timeout(); }; bool VM_Handshake::handshake_has_timed_out(jlong start_time) {
*** 119,142 **** } class VM_HandshakeOneThread: public VM_Handshake { JavaThread* _target; public: ! VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) : VM_Handshake(op), _target(target) {} void doit() { - DEBUG_ONLY(_op->check_state();) - jlong start_time_ns = 0; if (log_is_enabled(Info, handshake)) { start_time_ns = os::javaTimeNanos(); } ThreadsListHandle tlh; if (tlh.includes(_target)) { ! set_handshake(_target); } else { log_handshake_info(start_time_ns, _op->name(), 0, 0, "(thread dead)"); return; } --- 111,132 ---- } class VM_HandshakeOneThread: public VM_Handshake { JavaThread* _target; public: ! VM_HandshakeOneThread(HandshakeOperation* op, JavaThread* target) : VM_Handshake(op), _target(target) {} void doit() { jlong start_time_ns = 0; if (log_is_enabled(Info, handshake)) { start_time_ns = os::javaTimeNanos(); } ThreadsListHandle tlh; if (tlh.includes(_target)) { ! _target->set_handshake_operation(_op); } else { log_handshake_info(start_time_ns, _op->name(), 0, 0, "(thread dead)"); return; }
*** 145,193 **** bool by_vm_thread = false; do { if (handshake_has_timed_out(timeout_start_time)) { handle_timeout(); } ! by_vm_thread = _target->handshake_try_process_by_vmThread(); ! } while (!poll_for_completed_thread()); ! DEBUG_ONLY(_op->check_state();) log_handshake_info(start_time_ns, _op->name(), 1, by_vm_thread ? 1 : 0); } VMOp_Type type() const { return VMOp_HandshakeOneThread; } bool executed() const { return _op->executed(); } }; class VM_HandshakeAllThreads: public VM_Handshake { public: ! VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {} void doit() { - DEBUG_ONLY(_op->check_state();) - jlong start_time_ns = 0; if (log_is_enabled(Info, handshake)) { start_time_ns = os::javaTimeNanos(); } int handshake_executed_by_vm_thread = 0; JavaThreadIteratorWithHandle jtiwh; int number_of_threads_issued = 0; for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { ! set_handshake(thr); number_of_threads_issued++; } if (number_of_threads_issued < 1) { log_handshake_info(start_time_ns, _op->name(), 0, 0); return; } log_trace(handshake)("Threads signaled, begin processing blocked threads by VMThread"); const jlong start_time = os::elapsed_counter(); - int number_of_threads_completed = 0; do { // Check if handshake operation has timed out if (handshake_has_timed_out(start_time)) { handle_timeout(); } --- 135,188 ---- bool by_vm_thread = false; do { if (handshake_has_timed_out(timeout_start_time)) { handle_timeout(); } ! by_vm_thread = _target->handshake_try_process(_op); ! } while (!_op->is_completed()); ! ! // This pairs up with the release store in do_handshake(). It prevents future ! // loads from floating above the load of _pending_threads in is_completed() ! // and thus prevents reading stale data modified in the handshake closure ! // by the Handshakee. ! OrderAccess::acquire(); ! log_handshake_info(start_time_ns, _op->name(), 1, by_vm_thread ? 1 : 0); } VMOp_Type type() const { return VMOp_HandshakeOneThread; } bool executed() const { return _op->executed(); } }; class VM_HandshakeAllThreads: public VM_Handshake { public: ! VM_HandshakeAllThreads(HandshakeOperation* op) : VM_Handshake(op) {} void doit() { jlong start_time_ns = 0; if (log_is_enabled(Info, handshake)) { start_time_ns = os::javaTimeNanos(); } int handshake_executed_by_vm_thread = 0; JavaThreadIteratorWithHandle jtiwh; int number_of_threads_issued = 0; for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { ! thr->set_handshake_operation(_op); number_of_threads_issued++; } if (number_of_threads_issued < 1) { log_handshake_info(start_time_ns, _op->name(), 0, 0); return; } + // _op was created with a count == 1 so don't double count. + _op->add_target_count(number_of_threads_issued - 1); log_trace(handshake)("Threads signaled, begin processing blocked threads by VMThread"); const jlong start_time = os::elapsed_counter(); do { // Check if handshake operation has timed out if (handshake_has_timed_out(start_time)) { handle_timeout(); }
*** 196,226 **** // Observing a blocked state may of course be transient but the processing is guarded // by semaphores and we optimistically begin by working on the blocked threads jtiwh.rewind(); for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { // A new thread on the ThreadsList will not have an operation, ! // hence it is skipped in handshake_process_by_vmthread. ! if (thr->handshake_try_process_by_vmThread()) { handshake_executed_by_vm_thread++; } } ! while (poll_for_completed_thread()) { ! // Includes canceled operations by exiting threads. ! number_of_threads_completed++; ! } ! } while (number_of_threads_issued > number_of_threads_completed); ! assert(number_of_threads_issued == number_of_threads_completed, "Must be the same"); ! DEBUG_ONLY(_op->check_state();) log_handshake_info(start_time_ns, _op->name(), number_of_threads_issued, handshake_executed_by_vm_thread); } VMOp_Type type() const { return VMOp_HandshakeAllThreads; } }; ! void HandshakeThreadsOperation::do_handshake(JavaThread* thread) { jlong start_time_ns = 0; if (log_is_enabled(Debug, handshake, task)) { start_time_ns = os::javaTimeNanos(); } --- 191,220 ---- // Observing a blocked state may of course be transient but the processing is guarded // by semaphores and we optimistically begin by working on the blocked threads jtiwh.rewind(); for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { // A new thread on the ThreadsList will not have an operation, ! // hence it is skipped in handshake_try_process. ! if (thr->handshake_try_process(_op)) { handshake_executed_by_vm_thread++; } } ! } while (!_op->is_completed()); ! // This pairs up with the release store in do_handshake(). It prevents future ! // loads from floating above the load of _pending_threads in is_completed() ! // and thus prevents reading stale data modified in the handshake closure ! // by the Handshakee. ! OrderAccess::acquire(); log_handshake_info(start_time_ns, _op->name(), number_of_threads_issued, handshake_executed_by_vm_thread); } VMOp_Type type() const { return VMOp_HandshakeAllThreads; } }; ! void HandshakeOperation::do_handshake(JavaThread* thread) { jlong start_time_ns = 0; if (log_is_enabled(Debug, handshake, task)) { start_time_ns = os::javaTimeNanos(); }
*** 234,370 **** jlong completion_time = os::javaTimeNanos() - start_time_ns; log_debug(handshake, task)("Operation: %s for thread " PTR_FORMAT ", is_vm_thread: %s, completed in " JLONG_FORMAT " ns", name(), p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()), completion_time); } ! // Use the semaphore to inform the VM thread that we have completed the operation ! _done.signal(); ! // It is no longer safe to refer to 'this' as the VMThread may have destroyed this operation } void Handshake::execute(HandshakeClosure* thread_cl) { ! HandshakeThreadsOperation cto(thread_cl); VM_HandshakeAllThreads handshake(&cto); VMThread::execute(&handshake); } bool Handshake::execute(HandshakeClosure* thread_cl, JavaThread* target) { ! HandshakeThreadsOperation cto(thread_cl); VM_HandshakeOneThread handshake(&cto, target); VMThread::execute(&handshake); return handshake.executed(); } ! HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _thread_in_process_handshake(false) { ! DEBUG_ONLY(_vmthread_processing_handshake = false;) } ! void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) { _operation = op; ! SafepointMechanism::arm_local_poll_release(target); } ! void HandshakeState::clear_handshake(JavaThread* target) { _operation = NULL; ! SafepointMechanism::disarm_if_needed(target, true /* release */); } ! void HandshakeState::process_self_inner(JavaThread* thread) { ! assert(Thread::current() == thread, "should call from thread"); ! assert(!thread->is_terminated(), "should not be a terminated thread"); ! assert(thread->thread_state() != _thread_blocked, "should not be in a blocked state"); ! assert(thread->thread_state() != _thread_in_native, "should not be in native"); do { ! ThreadInVMForHandshake tivm(thread); ! if (!_semaphore.trywait()) { ! _semaphore.wait_with_safepoint_check(thread); } ! HandshakeOperation* op = Atomic::load_acquire(&_operation); if (op != NULL) { ! HandleMark hm(thread); ! CautiouslyPreserveExceptionMark pem(thread); ! // Disarm before execute the operation ! clear_handshake(thread); ! op->do_handshake(thread); } ! _semaphore.signal(); } while (has_operation()); } ! bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) { // handshake_safe may only be called with polls armed. ! // VM thread controls this by first claiming the handshake via claim_handshake_for_vmthread. ! return SafepointSynchronize::handshake_safe(target); } ! static bool possibly_vmthread_can_process_handshake(JavaThread* target) { // Note that this method is allowed to produce false positives. ! if (target->is_ext_suspended()) { return true; } ! if (target->is_terminated()) { return true; } ! switch (target->thread_state()) { case _thread_in_native: // native threads are safe if they have no java stack or have walkable stack ! return !target->has_last_Java_frame() || target->frame_anchor()->walkable(); case _thread_blocked: return true; default: return false; } } ! bool HandshakeState::claim_handshake_for_vmthread() { ! if (!_semaphore.trywait()) { return false; } ! if (has_operation()) { return true; } ! _semaphore.signal(); return false; } ! bool HandshakeState::try_process_by_vmThread(JavaThread* target) { ! assert(Thread::current()->is_VM_thread(), "should call from vm thread"); ! if (!has_operation()) { // JT has already cleared its handshake return false; } ! if (!possibly_vmthread_can_process_handshake(target)) { // JT is observed in an unsafe state, it must notice the handshake itself return false; } // Claim the semaphore if there still an operation to be executed. ! if (!claim_handshake_for_vmthread()) { return false; } // If we own the semaphore at this point and while owning the semaphore // can observe a safe state the thread cannot possibly continue without // getting caught by the semaphore. bool executed = false; ! if (vmthread_can_process_handshake(target)) { ! guarantee(!_semaphore.trywait(), "we should already own the semaphore"); ! log_trace(handshake)("Processing handshake by VMThtread"); ! DEBUG_ONLY(_vmthread_processing_handshake = true;) ! _operation->do_handshake(target); ! DEBUG_ONLY(_vmthread_processing_handshake = false;) ! // Disarm after VM thread have executed the operation. ! clear_handshake(target); executed = true; } // Release the thread ! _semaphore.signal(); return executed; } --- 228,441 ---- jlong completion_time = os::javaTimeNanos() - start_time_ns; log_debug(handshake, task)("Operation: %s for thread " PTR_FORMAT ", is_vm_thread: %s, completed in " JLONG_FORMAT " ns", name(), p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()), completion_time); } ! // Inform VMThread/Handshaker that we have completed the operation. ! // When this is executed by the Handshakee we need a release store ! // here to make sure memory operations executed in the handshake ! // closure are visible to the VMThread/Handshaker after it reads ! // that the operation has completed. ! Atomic::dec(&_pending_threads, memory_order_release); ! // It is no longer safe to refer to 'this' as the VMThread/Handshaker may have destroyed this operation } void Handshake::execute(HandshakeClosure* thread_cl) { ! HandshakeOperation cto(thread_cl); VM_HandshakeAllThreads handshake(&cto); VMThread::execute(&handshake); } bool Handshake::execute(HandshakeClosure* thread_cl, JavaThread* target) { ! HandshakeOperation cto(thread_cl); VM_HandshakeOneThread handshake(&cto, target); VMThread::execute(&handshake); return handshake.executed(); } ! bool Handshake::execute_direct(HandshakeClosure* thread_cl, JavaThread* target) { ! JavaThread* self = JavaThread::current(); ! HandshakeOperation op(thread_cl, /*is_direct*/ true); ! ! jlong start_time_ns = 0; ! if (log_is_enabled(Info, handshake)) { ! start_time_ns = os::javaTimeNanos(); ! } ! ! ThreadsListHandle tlh; ! if (tlh.includes(target)) { ! target->set_handshake_operation(&op); ! } else { ! log_handshake_info(start_time_ns, op.name(), 0, 0, "(thread dead)"); ! return false; ! } ! ! bool by_handshaker = false; ! while (!op.is_completed()) { ! by_handshaker = target->handshake_try_process(&op); ! // Check for pending handshakes to avoid possible deadlocks where our ! // target is trying to handshake us. ! if (SafepointMechanism::should_block(self)) { ! ThreadBlockInVM tbivm(self); ! } ! } ! ! // This pairs up with the release store in do_handshake(). It prevents future ! // loads from floating above the load of _pending_threads in is_completed() ! // and thus prevents reading stale data modified in the handshake closure ! // by the Handshakee. ! OrderAccess::acquire(); ! ! log_handshake_info(start_time_ns, op.name(), 1, by_handshaker ? 1 : 0); ! ! return op.executed(); ! } ! ! HandshakeState::HandshakeState() : ! _operation(NULL), ! _operation_direct(NULL), ! _handshake_turn_sem(1), ! _processing_sem(1), ! _thread_in_process_handshake(false) ! { ! DEBUG_ONLY(_active_handshaker = NULL;) } ! void HandshakeState::set_operation(HandshakeOperation* op) { ! if (!op->is_direct()) { ! assert(Thread::current()->is_VM_thread(), "should be the VMThread"); _operation = op; ! } else { ! assert(Thread::current()->is_Java_thread(), "should be a JavaThread"); ! // Serialize direct handshakes so that only one proceeds at a time for a given target ! _handshake_turn_sem.wait_with_safepoint_check(JavaThread::current()); ! _operation_direct = op; ! } ! SafepointMechanism::arm_local_poll_release(_handshakee); } ! void HandshakeState::clear_handshake(bool is_direct) { ! if (!is_direct) { _operation = NULL; ! } else { ! _operation_direct = NULL; ! _handshake_turn_sem.signal(); ! } } ! void HandshakeState::process_self_inner() { ! assert(Thread::current() == _handshakee, "should call from _handshakee"); ! assert(!_handshakee->is_terminated(), "should not be a terminated thread"); ! assert(_handshakee->thread_state() != _thread_blocked, "should not be in a blocked state"); ! assert(_handshakee->thread_state() != _thread_in_native, "should not be in native"); ! JavaThread* self = _handshakee; do { ! ThreadInVMForHandshake tivm(self); ! if (!_processing_sem.trywait()) { ! _processing_sem.wait_with_safepoint_check(self); ! } ! if (has_operation()) { ! HandleMark hm(self); ! CautiouslyPreserveExceptionMark pem(self); ! HandshakeOperation * op = _operation; ! if (op != NULL) { ! // Disarm before executing the operation ! clear_handshake(/*is_direct*/ false); ! op->do_handshake(self); } ! op = _operation_direct; if (op != NULL) { ! // Disarm before executing the operation ! clear_handshake(/*is_direct*/ true); ! op->do_handshake(self); } ! } ! _processing_sem.signal(); } while (has_operation()); } ! bool HandshakeState::can_process_handshake() { // handshake_safe may only be called with polls armed. ! // Handshaker controls this by first claiming the handshake via claim_handshake(). ! return SafepointSynchronize::handshake_safe(_handshakee); } ! bool HandshakeState::possibly_can_process_handshake() { // Note that this method is allowed to produce false positives. ! if (_handshakee->is_ext_suspended()) { return true; } ! if (_handshakee->is_terminated()) { return true; } ! switch (_handshakee->thread_state()) { case _thread_in_native: // native threads are safe if they have no java stack or have walkable stack ! return !_handshakee->has_last_Java_frame() || _handshakee->frame_anchor()->walkable(); case _thread_blocked: return true; default: return false; } } ! bool HandshakeState::claim_handshake(bool is_direct) { ! if (!_processing_sem.trywait()) { return false; } ! if (has_specific_operation(is_direct)){ return true; } ! _processing_sem.signal(); return false; } ! bool HandshakeState::try_process(HandshakeOperation* op) { ! bool is_direct = op->is_direct(); ! if (!has_specific_operation(is_direct)){ // JT has already cleared its handshake return false; } ! if (!possibly_can_process_handshake()) { // JT is observed in an unsafe state, it must notice the handshake itself return false; } // Claim the semaphore if there still an operation to be executed. ! if (!claim_handshake(is_direct)) { ! return false; ! } ! ! // Check if the handshake operation is the same as the one we meant to execute. The ! // handshake could have been already processed by the handshakee and a new handshake ! // by another JavaThread might be in progress. ! if (is_direct && op != _operation_direct) { ! _processing_sem.signal(); return false; } // If we own the semaphore at this point and while owning the semaphore // can observe a safe state the thread cannot possibly continue without // getting caught by the semaphore. bool executed = false; ! if (can_process_handshake()) { ! guarantee(!_processing_sem.trywait(), "we should already own the semaphore"); ! log_trace(handshake)("Processing handshake by %s", Thread::current()->is_VM_thread() ? "VMThread" : "Handshaker"); ! DEBUG_ONLY(_active_handshaker = Thread::current();) ! op->do_handshake(_handshakee); ! DEBUG_ONLY(_active_handshaker = NULL;) ! // Disarm after we have executed the operation. ! clear_handshake(is_direct); executed = true; } // Release the thread ! _processing_sem.signal(); return executed; }
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