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