1 /* 2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "runtime/threadCritical.hpp" 27 #include "thread_windows.inline.hpp" 28 29 // OS-includes here 30 # include <windows.h> 31 # include <winbase.h> 32 33 // 34 // See threadCritical.hpp for details of this class. 35 // 36 37 static bool initialized = false; 38 static volatile jint lock_count = -1; 39 static HANDLE lock_event; 40 static DWORD lock_owner = -1; 41 42 // 43 // Note that Microsoft's critical region code contains a race 44 // condition, and is not suitable for use. A thread holding the 45 // critical section cannot safely suspend a thread attempting 46 // to enter the critical region. The failure mode is that both 47 // threads are permanently suspended. 48 // 49 // I experiemented with the use of ordinary windows mutex objects 50 // and found them ~30 times slower than the critical region code. 51 // 52 53 void ThreadCritical::initialize() { 54 } 55 56 void ThreadCritical::release() { 57 assert(lock_owner == -1, "Mutex being deleted while owned."); 58 assert(lock_count == -1, "Mutex being deleted while recursively locked"); 59 assert(lock_event != NULL, "Sanity check"); 60 CloseHandle(lock_event); 61 } 62 63 ThreadCritical::ThreadCritical() { 64 DWORD current_thread = GetCurrentThreadId(); 65 66 if (lock_owner != current_thread) { 67 // Grab the lock before doing anything. 68 while (Atomic::cmpxchg(0, &lock_count, -1) != -1) { 69 if (initialized) { 70 DWORD ret = WaitForSingleObject(lock_event, INFINITE); 71 assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject"); 72 } 73 } 74 75 // Make sure the event object is allocated. 76 if (!initialized) { 77 // Locking will not work correctly unless this is autoreset. 78 lock_event = CreateEvent(NULL, false, false, NULL); 79 initialized = true; 80 } 81 82 assert(lock_owner == -1, "Lock acquired illegally."); 83 lock_owner = current_thread; 84 } else { 85 // Atomicity isn't required. Bump the recursion count. 86 lock_count++; 87 } 88 89 assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally."); 90 } 91 92 ThreadCritical::~ThreadCritical() { 93 assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread"); 94 assert(lock_count >= 0, "Attempt to unlock when already unlocked"); 95 96 if (lock_count == 0) { 97 // We're going to unlock 98 lock_owner = -1; 99 lock_count = -1; 100 // No lost wakeups, lock_event stays signaled until reset. 101 DWORD ret = SetEvent(lock_event); 102 assert(ret != 0, "unexpected return value from SetEvent"); 103 } else { 104 // Just unwinding a recursive lock; 105 lock_count--; 106 } 107 }