Mercurial > hg > truffle
annotate src/share/vm/memory/gcLocker.cpp @ 12301:2c022e432e10
8024974: Incorrect use of GC_locker::is_active()
Summary: SymbolTable and StringTable can make calls to GC_locker::is_active() outside a safepoint. This isn't safe because the GC_locker active state (lock count) is only updated at a safepoint and only remains valid as long as _needs_gc is true. However, outside a safepoint_needs_gc can change to false at any time, which makes it impossible to do a correct call to is_active() in that context. In this case these calls can just be removed since the input argument to basic_add() should never be on the heap and so there's no need to check the GC_locker state. This change also adjusts the assert() in is_active() to makes sure all calls to this function are always done under a safepoint.
Reviewed-by: brutisso, dcubed
Contributed-by: per.liden@oracle.com
| author | stefank |
|---|---|
| date | Fri, 20 Sep 2013 10:53:28 +0200 |
| parents | 09d00c18e323 |
| children | de6a9e811145 |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved. |
| 0 | 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 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 1972 | 25 #include "precompiled.hpp" |
| 26 #include "memory/gcLocker.inline.hpp" | |
| 27 #include "memory/resourceArea.hpp" | |
| 28 #include "memory/sharedHeap.hpp" | |
| 0 | 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; | |
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34 |
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35 #ifdef ASSERT |
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36 volatile jint GC_locker::_debug_jni_lock_count = 0; |
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37 #endif |
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38 |
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39 |
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40 #ifdef ASSERT |
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41 void GC_locker::verify_critical_count() { |
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42 if (SafepointSynchronize::is_at_safepoint()) { |
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43 assert(!needs_gc() || _debug_jni_lock_count == _jni_lock_count, "must agree"); |
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44 int count = 0; |
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45 // Count the number of threads with critical operations in progress |
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46 for (JavaThread* thr = Threads::first(); thr; thr = thr->next()) { |
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47 if (thr->in_critical()) { |
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48 count++; |
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49 } |
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50 } |
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51 if (_jni_lock_count != count) { |
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52 tty->print_cr("critical counts don't match: %d != %d", _jni_lock_count, count); |
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53 for (JavaThread* thr = Threads::first(); thr; thr = thr->next()) { |
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54 if (thr->in_critical()) { |
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55 tty->print_cr(INTPTR_FORMAT " in_critical %d", thr, thr->in_critical()); |
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56 } |
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57 } |
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58 } |
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59 assert(_jni_lock_count == count, "must be equal"); |
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60 } |
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61 } |
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62 #endif |
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63 |
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64 bool GC_locker::check_active_before_gc() { |
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65 assert(SafepointSynchronize::is_at_safepoint(), "only read at safepoint"); |
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66 if (is_active() && !_needs_gc) { |
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67 verify_critical_count(); |
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68 _needs_gc = true; |
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69 if (PrintJNIGCStalls && PrintGCDetails) { |
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70 ResourceMark rm; // JavaThread::name() allocates to convert to UTF8 |
| 4944 | 71 gclog_or_tty->print_cr("%.3f: Setting _needs_gc. Thread \"%s\" %d locked.", |
| 72 gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count); | |
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73 } |
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74 |
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75 } |
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76 return is_active(); |
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77 } |
| 0 | 78 |
| 79 void GC_locker::stall_until_clear() { | |
| 80 assert(!JavaThread::current()->in_critical(), "Would deadlock"); | |
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81 MutexLocker ml(JNICritical_lock); |
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82 |
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83 if (needs_gc()) { |
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84 if (PrintJNIGCStalls && PrintGCDetails) { |
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85 ResourceMark rm; // JavaThread::name() allocates to convert to UTF8 |
| 4944 | 86 gclog_or_tty->print_cr("%.3f: Allocation failed. Thread \"%s\" is stalled by JNI critical section, %d locked.", |
| 87 gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count); | |
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88 } |
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89 } |
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90 |
| 0 | 91 // Wait for _needs_gc to be cleared |
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92 while (needs_gc()) { |
| 0 | 93 JNICritical_lock->wait(); |
| 94 } | |
| 95 } | |
| 96 | |
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97 void GC_locker::jni_lock(JavaThread* thread) { |
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98 assert(!thread->in_critical(), "shouldn't currently be in a critical region"); |
| 0 | 99 MutexLocker mu(JNICritical_lock); |
| 100 // Block entering threads if we know at least one thread is in a | |
| 101 // JNI critical region and we need a GC. | |
| 102 // We check that at least one thread is in a critical region before | |
| 103 // blocking because blocked threads are woken up by a thread exiting | |
| 104 // a JNI critical region. | |
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105 while ((needs_gc() && is_jni_active()) || _doing_gc) { |
| 0 | 106 JNICritical_lock->wait(); |
| 107 } | |
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108 thread->enter_critical(); |
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109 _jni_lock_count++; |
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110 increment_debug_jni_lock_count(); |
| 0 | 111 } |
| 112 | |
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113 void GC_locker::jni_unlock(JavaThread* thread) { |
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114 assert(thread->in_last_critical(), "should be exiting critical region"); |
| 0 | 115 MutexLocker mu(JNICritical_lock); |
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116 _jni_lock_count--; |
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117 decrement_debug_jni_lock_count(); |
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118 thread->exit_critical(); |
| 0 | 119 if (needs_gc() && !is_jni_active()) { |
| 120 // We're the last thread out. Cause a GC to occur. | |
| 121 // GC will also check is_active, so this check is not | |
| 122 // strictly needed. It's added here to make it clear that | |
| 123 // the GC will NOT be performed if any other caller | |
| 124 // of GC_locker::lock() still needs GC locked. | |
| 12301 | 125 if (!is_active_internal()) { |
| 0 | 126 _doing_gc = true; |
| 127 { | |
| 128 // Must give up the lock while at a safepoint | |
| 129 MutexUnlocker munlock(JNICritical_lock); | |
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130 if (PrintJNIGCStalls && PrintGCDetails) { |
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131 ResourceMark rm; // JavaThread::name() allocates to convert to UTF8 |
| 4944 | 132 gclog_or_tty->print_cr("%.3f: Thread \"%s\" is performing GC after exiting critical section, %d locked", |
| 133 gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count); | |
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134 } |
| 0 | 135 Universe::heap()->collect(GCCause::_gc_locker); |
| 136 } | |
| 137 _doing_gc = false; | |
| 138 } | |
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139 |
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140 _needs_gc = false; |
| 0 | 141 JNICritical_lock->notify_all(); |
| 142 } | |
| 143 } | |
| 144 | |
| 145 // Implementation of No_GC_Verifier | |
| 146 | |
| 147 #ifdef ASSERT | |
| 148 | |
| 149 No_GC_Verifier::No_GC_Verifier(bool verifygc) { | |
| 150 _verifygc = verifygc; | |
| 151 if (_verifygc) { | |
| 152 CollectedHeap* h = Universe::heap(); | |
| 153 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); | |
| 154 _old_invocations = h->total_collections(); | |
| 155 } | |
| 156 } | |
| 157 | |
| 158 | |
| 159 No_GC_Verifier::~No_GC_Verifier() { | |
| 160 if (_verifygc) { | |
| 161 CollectedHeap* h = Universe::heap(); | |
| 162 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); | |
| 163 if (_old_invocations != h->total_collections()) { | |
| 164 fatal("collection in a No_GC_Verifier secured function"); | |
| 165 } | |
| 166 } | |
| 167 } | |
| 168 | |
| 169 Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) { | |
| 170 _ngcv = ngcv; | |
| 171 if (_ngcv->_verifygc) { | |
| 172 // if we were verifying, then make sure that nothing is | |
| 173 // wrong before we "pause" verification | |
| 174 CollectedHeap* h = Universe::heap(); | |
| 175 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); | |
| 176 if (_ngcv->_old_invocations != h->total_collections()) { | |
| 177 fatal("collection in a No_GC_Verifier secured function"); | |
| 178 } | |
| 179 } | |
| 180 } | |
| 181 | |
| 182 | |
| 183 Pause_No_GC_Verifier::~Pause_No_GC_Verifier() { | |
| 184 if (_ngcv->_verifygc) { | |
| 185 // if we were verifying before, then reenable verification | |
| 186 CollectedHeap* h = Universe::heap(); | |
| 187 assert(!h->is_gc_active(), "GC active during No_GC_Verifier"); | |
| 188 _ngcv->_old_invocations = h->total_collections(); | |
| 189 } | |
| 190 } | |
| 191 | |
| 192 | |
| 193 // JRT_LEAF rules: | |
| 194 // A JRT_LEAF method may not interfere with safepointing by | |
| 195 // 1) acquiring or blocking on a Mutex or JavaLock - checked | |
| 196 // 2) allocating heap memory - checked | |
| 197 // 3) executing a VM operation - checked | |
| 198 // 4) executing a system call (including malloc) that could block or grab a lock | |
| 199 // 5) invoking GC | |
| 200 // 6) reaching a safepoint | |
| 201 // 7) running too long | |
| 202 // Nor may any method it calls. | |
| 203 JRT_Leaf_Verifier::JRT_Leaf_Verifier() | |
| 204 : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC()) | |
| 205 { | |
| 206 } | |
| 207 | |
| 208 JRT_Leaf_Verifier::~JRT_Leaf_Verifier() | |
| 209 { | |
| 210 } | |
| 211 | |
| 212 bool JRT_Leaf_Verifier::should_verify_GC() { | |
| 213 switch (JavaThread::current()->thread_state()) { | |
| 214 case _thread_in_Java: | |
| 215 // is in a leaf routine, there must be no safepoint. | |
| 216 return true; | |
| 217 case _thread_in_native: | |
| 218 // A native thread is not subject to safepoints. | |
| 219 // Even while it is in a leaf routine, GC is ok | |
| 220 return false; | |
| 221 default: | |
| 222 // Leaf routines cannot be called from other contexts. | |
| 223 ShouldNotReachHere(); | |
| 224 return false; | |
| 225 } | |
| 226 } | |
| 227 #endif |