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1 /*
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2 * Copyright 2001-2003 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_threadCritical_windows.cpp.incl"
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27
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28 // OS-includes here
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29 # include <windows.h>
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30 # include <winbase.h>
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31
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32 //
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33 // See threadCritical.hpp for details of this class.
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34 //
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35
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36 static bool initialized = false;
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37 static volatile jint lock_count = -1;
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38 static HANDLE lock_event;
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39 static DWORD lock_owner = -1;
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40
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41 //
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42 // Note that Microsoft's critical region code contains a race
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43 // condition, and is not suitable for use. A thread holding the
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44 // critical section cannot safely suspend a thread attempting
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45 // to enter the critical region. The failure mode is that both
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46 // threads are permanently suspended.
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47 //
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48 // I experiemented with the use of ordinary windows mutex objects
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49 // and found them ~30 times slower than the critical region code.
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50 //
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51
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52 void ThreadCritical::initialize() {
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53 }
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54
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55 void ThreadCritical::release() {
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56 assert(lock_owner == -1, "Mutex being deleted while owned.");
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57 assert(lock_count == -1, "Mutex being deleted while recursively locked");
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58 assert(lock_event != NULL, "Sanity check");
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59 CloseHandle(lock_event);
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60 }
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61
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62 ThreadCritical::ThreadCritical() {
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63 DWORD current_thread = GetCurrentThreadId();
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64
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65 if (lock_owner != current_thread) {
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66 // Grab the lock before doing anything.
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67 while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {
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68 if (initialized) {
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69 DWORD ret = WaitForSingleObject(lock_event, INFINITE);
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70 assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");
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71 }
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72 }
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73
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74 // Make sure the event object is allocated.
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75 if (!initialized) {
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76 // Locking will not work correctly unless this is autoreset.
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77 lock_event = CreateEvent(NULL, false, false, NULL);
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78 initialized = true;
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79 }
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80
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81 assert(lock_owner == -1, "Lock acquired illegally.");
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82 lock_owner = current_thread;
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83 } else {
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84 // Atomicity isn't required. Bump the recursion count.
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85 lock_count++;
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86 }
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87
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88 assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");
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89 }
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90
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91 ThreadCritical::~ThreadCritical() {
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92 assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");
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93 assert(lock_count >= 0, "Attempt to unlock when already unlocked");
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94
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95 if (lock_count == 0) {
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96 // We're going to unlock
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97 lock_owner = -1;
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98 lock_count = -1;
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99 // No lost wakeups, lock_event stays signaled until reset.
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100 DWORD ret = SetEvent(lock_event);
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101 assert(ret != 0, "unexpected return value from SetEvent");
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102 } else {
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103 // Just unwinding a recursive lock;
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104 lock_count--;
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105 }
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106 }
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