Mercurial > hg > graal-jvmci-8
view src/share/vm/runtime/vmThread.hpp @ 1716:be3f9c242c9d
6948538: CMS: BOT walkers can fall into object allocation and initialization cracks
Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode.
Reviewed-by: chrisphi, johnc, poonam
author | ysr |
---|---|
date | Mon, 16 Aug 2010 15:58:42 -0700 |
parents | c18cbe5936b8 |
children | f95d63e2154a |
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/* * Copyright (c) 1998, 2006, Oracle and/or its affiliates. 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. * */ // // Prioritized queue of VM operations. // // Encapsulates both queue management and // and priority policy // class VMOperationQueue : public CHeapObj { private: enum Priorities { SafepointPriority, // Highest priority (operation executed at a safepoint) MediumPriority, // Medium priority nof_priorities }; // We maintain a doubled linked list, with explicit count. int _queue_length[nof_priorities]; int _queue_counter; VM_Operation* _queue [nof_priorities]; // we also allow the vmThread to register the ops it has drained so we // can scan them from oops_do VM_Operation* _drain_list; // Double-linked non-empty list insert. void insert(VM_Operation* q,VM_Operation* n); void unlink(VM_Operation* q); // Basic queue manipulation bool queue_empty (int prio); void queue_add_front (int prio, VM_Operation *op); void queue_add_back (int prio, VM_Operation *op); VM_Operation* queue_remove_front(int prio); void queue_oops_do(int queue, OopClosure* f); void drain_list_oops_do(OopClosure* f); VM_Operation* queue_drain(int prio); // lock-free query: may return the wrong answer but must not break bool queue_peek(int prio) { return _queue_length[prio] > 0; } public: VMOperationQueue(); // Highlevel operations. Encapsulates policy bool add(VM_Operation *op); VM_Operation* remove_next(); // Returns next or null VM_Operation* remove_next_at_safepoint_priority() { return queue_remove_front(SafepointPriority); } VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); } void set_drain_list(VM_Operation* list) { _drain_list = list; } bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); } // GC support void oops_do(OopClosure* f); void verify_queue(int prio) PRODUCT_RETURN; }; // // A single VMThread (the primordial thread) spawns all other threads // and is itself used by other threads to offload heavy vm operations // like scavenge, garbage_collect etc. // class VMThread: public NamedThread { private: static ThreadPriority _current_priority; static bool _should_terminate; static bool _terminated; static Monitor * _terminate_lock; static PerfCounter* _perf_accumulated_vm_operation_time; void evaluate_operation(VM_Operation* op); public: // Constructor VMThread(); // Tester bool is_VM_thread() const { return true; } bool is_GC_thread() const { return true; } // The ever running loop for the VMThread void loop(); // Called to stop the VM thread static void wait_for_vm_thread_exit(); static bool should_terminate() { return _should_terminate; } static bool is_terminated() { return _terminated == true; } // Execution of vm operation static void execute(VM_Operation* op); // Returns the current vm operation if any. static VM_Operation* vm_operation() { return _cur_vm_operation; } // Returns the single instance of VMThread. static VMThread* vm_thread() { return _vm_thread; } // GC support void oops_do(OopClosure* f, CodeBlobClosure* cf); // Debugging void print_on(outputStream* st) const; void print() const { print_on(tty); } void verify(); // Performance measurement static PerfCounter* perf_accumulated_vm_operation_time() { return _perf_accumulated_vm_operation_time; } // Entry for starting vm thread virtual void run(); // Creations/Destructions static void create(); static void destroy(); private: // VM_Operation support static VM_Operation* _cur_vm_operation; // Current VM operation static VMOperationQueue* _vm_queue; // Queue (w/ policy) of VM operations // Pointer to single-instance of VM thread static VMThread* _vm_thread; };