Mercurial > hg > graal-jvmci-8
view src/share/vm/gc_implementation/shared/concurrentGCThread.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 |
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date | Mon, 16 Aug 2010 15:58:42 -0700 |
parents | c18cbe5936b8 |
children | f95d63e2154a |
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/* * Copyright (c) 2001, 2009, 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. * */ class VoidClosure; // A SuspendibleThreadSet is (obviously) a set of threads that can be // suspended. A thread can join and later leave the set, and periodically // yield. If some thread (not in the set) requests, via suspend_all, that // the threads be suspended, then the requesting thread is blocked until // all the threads in the set have yielded or left the set. (Threads may // not enter the set when an attempted suspension is in progress.) The // suspending thread later calls resume_all, allowing the suspended threads // to continue. class SuspendibleThreadSet { Monitor* _m; int _async; bool _async_stop; int _async_stopped; bool _initialized; double _suspend_all_start; void initialize_work(); public: SuspendibleThreadSet() : _initialized(false) {} // Add the current thread to the set. May block if a suspension // is in progress. void join(); // Removes the current thread from the set. void leave(); // Returns "true" iff an suspension is in progress. bool should_yield() { return _async_stop; } // Suspends the current thread if a suspension is in progress (for // the duration of the suspension.) void yield(const char* id); // Return when all threads in the set are suspended. void suspend_all(); // Allow suspended threads to resume. void resume_all(); // Redundant initializations okay. void initialize() { // Double-check dirty read idiom. if (!_initialized) initialize_work(); } }; class ConcurrentGCThread: public NamedThread { friend class VMStructs; protected: bool _should_terminate; bool _has_terminated; enum CGC_flag_type { CGC_nil = 0x0, CGC_dont_suspend = 0x1, CGC_CGC_safepoint = 0x2, CGC_VM_safepoint = 0x4 }; static int _CGC_flag; static bool CGC_flag_is_set(int b) { return (_CGC_flag & b) != 0; } static int set_CGC_flag(int b) { return _CGC_flag |= b; } static int reset_CGC_flag(int b) { return _CGC_flag &= ~b; } void stopWorldAndDo(VoidClosure* op); // All instances share this one set. static SuspendibleThreadSet _sts; // Create and start the thread (setting it's priority high.) void create_and_start(); // Do initialization steps in the thread: record stack base and size, // init thread local storage, set JNI handle block. void initialize_in_thread(); // Wait until Universe::is_fully_initialized(); void wait_for_universe_init(); // Record that the current thread is terminating, and will do more // concurrent work. void terminate(); public: // Constructor ConcurrentGCThread(); ~ConcurrentGCThread() {} // Exists to call NamedThread destructor. // Tester bool is_ConcurrentGC_thread() const { return true; } static void safepoint_synchronize(); static void safepoint_desynchronize(); // All overridings should probably do _sts::yield, but we allow // overriding for distinguished debugging messages. Default is to do // nothing. virtual void yield() {} bool should_yield() { return _sts.should_yield(); } // they are prefixed by sts since there are already yield() and // should_yield() (non-static) methods in this class and it was an // easy way to differentiate them. static void stsYield(const char* id); static bool stsShouldYield(); static void stsJoin(); static void stsLeave(); }; // The SurrogateLockerThread is used by concurrent GC threads for // manipulating Java monitors, in particular, currently for // manipulating the pending_list_lock. XXX class SurrogateLockerThread: public JavaThread { friend class VMStructs; public: enum SLT_msg_type { empty = 0, // no message acquirePLL, // acquire pending list lock releaseAndNotifyPLL // notify and release pending list lock }; private: // the following are shared with the CMSThread SLT_msg_type _buffer; // communication buffer Monitor _monitor; // monitor controlling buffer BasicLock _basicLock; // used for PLL locking public: static SurrogateLockerThread* make(TRAPS); SurrogateLockerThread(); bool is_hidden_from_external_view() const { return true; } void loop(); // main method void manipulatePLL(SLT_msg_type msg); };