1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)gcLocker.cpp 1.52 07/05/17 15:54:45 JVM"
3 #endif
4 /*
5 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 # include "incls/_precompiled.incl"
29 # include "incls/_gcLocker.cpp.incl"
30
31 volatile jint GC_locker::_jni_lock_count = 0;
32 volatile jint GC_locker::_lock_count = 0;
33 volatile bool GC_locker::_needs_gc = false;
34 volatile bool GC_locker::_doing_gc = false;
35
36 void GC_locker::stall_until_clear() {
37 assert(!JavaThread::current()->in_critical(), "Would deadlock");
38 MutexLocker ml(JNICritical_lock);
39 // Wait for _needs_gc to be cleared
40 while (GC_locker::needs_gc()) {
41 JNICritical_lock->wait();
42 }
43 }
44
45 void GC_locker::jni_lock_slow() {
46 MutexLocker mu(JNICritical_lock);
47 // Block entering threads if we know at least one thread is in a
48 // JNI critical region and we need a GC.
49 // We check that at least one thread is in a critical region before
50 // blocking because blocked threads are woken up by a thread exiting
51 // a JNI critical region.
52 while ((is_jni_active() && needs_gc()) || _doing_gc) {
53 JNICritical_lock->wait();
54 }
55 jni_lock();
56 }
57
58 void GC_locker::jni_unlock_slow() {
59 MutexLocker mu(JNICritical_lock);
60 jni_unlock();
61 if (needs_gc() && !is_jni_active()) {
62 // We're the last thread out. Cause a GC to occur.
63 // GC will also check is_active, so this check is not
64 // strictly needed. It's added here to make it clear that
65 // the GC will NOT be performed if any other caller
66 // of GC_locker::lock() still needs GC locked.
67 if (!is_active()) {
68 _doing_gc = true;
69 {
70 // Must give up the lock while at a safepoint
71 MutexUnlocker munlock(JNICritical_lock);
72 Universe::heap()->collect(GCCause::_gc_locker);
73 }
74 _doing_gc = false;
75 }
76 clear_needs_gc();
77 JNICritical_lock->notify_all();
78 }
79 }
80
81 // Implementation of No_GC_Verifier
82
83 #ifdef ASSERT
84
85 No_GC_Verifier::No_GC_Verifier(bool verifygc) {
86 _verifygc = verifygc;
87 if (_verifygc) {
88 CollectedHeap* h = Universe::heap();
89 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
90 _old_invocations = h->total_collections();
91 }
92 }
93
94
95 No_GC_Verifier::~No_GC_Verifier() {
96 if (_verifygc) {
97 CollectedHeap* h = Universe::heap();
98 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
99 if (_old_invocations != h->total_collections()) {
100 fatal("collection in a No_GC_Verifier secured function");
101 }
102 }
103 }
104
105 Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {
106 _ngcv = ngcv;
107 if (_ngcv->_verifygc) {
108 // if we were verifying, then make sure that nothing is
109 // wrong before we "pause" verification
110 CollectedHeap* h = Universe::heap();
111 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
112 if (_ngcv->_old_invocations != h->total_collections()) {
113 fatal("collection in a No_GC_Verifier secured function");
114 }
115 }
116 }
117
118
119 Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {
120 if (_ngcv->_verifygc) {
121 // if we were verifying before, then reenable verification
122 CollectedHeap* h = Universe::heap();
123 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
124 _ngcv->_old_invocations = h->total_collections();
125 }
126 }
127
128
129 // JRT_LEAF rules:
130 // A JRT_LEAF method may not interfere with safepointing by
131 // 1) acquiring or blocking on a Mutex or JavaLock - checked
132 // 2) allocating heap memory - checked
133 // 3) executing a VM operation - checked
134 // 4) executing a system call (including malloc) that could block or grab a lock
135 // 5) invoking GC
136 // 6) reaching a safepoint
137 // 7) running too long
138 // Nor may any method it calls.
139 JRT_Leaf_Verifier::JRT_Leaf_Verifier()
140 : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())
141 {
142 }
143
144 JRT_Leaf_Verifier::~JRT_Leaf_Verifier()
145 {
146 }
147
148 bool JRT_Leaf_Verifier::should_verify_GC() {
149 switch (JavaThread::current()->thread_state()) {
150 case _thread_in_Java:
151 // is in a leaf routine, there must be no safepoint.
152 return true;
153 case _thread_in_native:
154 // A native thread is not subject to safepoints.
155 // Even while it is in a leaf routine, GC is ok
156 return false;
157 default:
158 // Leaf routines cannot be called from other contexts.
159 ShouldNotReachHere();
160 return false;
161 }
162 }
163 #endif