1 /* 2 * Copyright (c) 1997, 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 "memory/gcLocker.inline.hpp" 27 #include "memory/resourceArea.hpp" 28 #include "memory/sharedHeap.hpp" 29 30 volatile jint GC_locker::_jni_lock_count = 0; 31 volatile jint GC_locker::_lock_count = 0; 32 volatile bool GC_locker::_needs_gc = false; 33 volatile bool GC_locker::_doing_gc = false; 34 35 void GC_locker::stall_until_clear() { 36 assert(!JavaThread::current()->in_critical(), "Would deadlock"); 37 if (PrintJNIGCStalls && PrintGCDetails) { 38 ResourceMark rm; // JavaThread::name() allocates to convert to UTF8 39 gclog_or_tty->print_cr( 40 "Allocation failed. Thread \"%s\" is stalled by JNI critical section.", 41 JavaThread::current()->name()); 42 } 43 MutexLocker ml(JNICritical_lock); 44 // Wait for _needs_gc to be cleared 45 while (GC_locker::needs_gc()) { 46 JNICritical_lock->wait(); 47 } 48 } 49 50 void GC_locker::jni_lock_slow() { 51 MutexLocker mu(JNICritical_lock); 52 // Block entering threads if we know at least one thread is in a 53 // JNI critical region and we need a GC. 54 // We check that at least one thread is in a critical region before 55 // blocking because blocked threads are woken up by a thread exiting 56 // a JNI critical region. 57 while ((is_jni_active() && needs_gc()) || _doing_gc) { 58 JNICritical_lock->wait(); 59 } 60 jni_lock(); 61 } 62 63 void GC_locker::jni_unlock_slow() { 64 MutexLocker mu(JNICritical_lock); 65 jni_unlock(); 66 if (needs_gc() && !is_jni_active()) { 67 // We're the last thread out. Cause a GC to occur. 68 // GC will also check is_active, so this check is not 69 // strictly needed. It's added here to make it clear that 70 // the GC will NOT be performed if any other caller 71 // of GC_locker::lock() still needs GC locked. 72 if (!is_active()) { 73 _doing_gc = true; 74 { 75 // Must give up the lock while at a safepoint 76 MutexUnlocker munlock(JNICritical_lock); 77 Universe::heap()->collect(GCCause::_gc_locker); 78 } 79 _doing_gc = false; 80 } 81 clear_needs_gc(); 82 JNICritical_lock->notify_all(); 83 } 84 } 85 86 // Implementation of No_GC_Verifier 87 88 #ifdef ASSERT 89 90 No_GC_Verifier::No_GC_Verifier(bool verifygc) { 91 _verifygc = verifygc; 92 if (_verifygc) { 93 CollectedHeap* h = Universe::heap(); 94 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); 95 _old_invocations = h->total_collections(); 96 } 97 } 98 99 100 No_GC_Verifier::~No_GC_Verifier() { 101 if (_verifygc) { 102 CollectedHeap* h = Universe::heap(); 103 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); 104 if (_old_invocations != h->total_collections()) { 105 fatal("collection in a No_GC_Verifier secured function"); 106 } 107 } 108 } 109 110 Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) { 111 _ngcv = ngcv; 112 if (_ngcv->_verifygc) { 113 // if we were verifying, then make sure that nothing is 114 // wrong before we "pause" verification 115 CollectedHeap* h = Universe::heap(); 116 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); 117 if (_ngcv->_old_invocations != h->total_collections()) { 118 fatal("collection in a No_GC_Verifier secured function"); 119 } 120 } 121 } 122 123 124 Pause_No_GC_Verifier::~Pause_No_GC_Verifier() { 125 if (_ngcv->_verifygc) { 126 // if we were verifying before, then reenable verification 127 CollectedHeap* h = Universe::heap(); 128 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); 129 _ngcv->_old_invocations = h->total_collections(); 130 } 131 } 132 133 134 // JRT_LEAF rules: 135 // A JRT_LEAF method may not interfere with safepointing by 136 // 1) acquiring or blocking on a Mutex or JavaLock - checked 137 // 2) allocating heap memory - checked 138 // 3) executing a VM operation - checked 139 // 4) executing a system call (including malloc) that could block or grab a lock 140 // 5) invoking GC 141 // 6) reaching a safepoint 142 // 7) running too long 143 // Nor may any method it calls. 144 JRT_Leaf_Verifier::JRT_Leaf_Verifier() 145 : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC()) 146 { 147 } 148 149 JRT_Leaf_Verifier::~JRT_Leaf_Verifier() 150 { 151 } 152 153 bool JRT_Leaf_Verifier::should_verify_GC() { 154 switch (JavaThread::current()->thread_state()) { 155 case _thread_in_Java: 156 // is in a leaf routine, there must be no safepoint. 157 return true; 158 case _thread_in_native: 159 // A native thread is not subject to safepoints. 160 // Even while it is in a leaf routine, GC is ok 161 return false; 162 default: 163 // Leaf routines cannot be called from other contexts. 164 ShouldNotReachHere(); 165 return false; 166 } 167 } 168 #endif