1 /*
2 * Copyright (c) 1997, 2008, 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 "incls/_precompiled.incl"
26 # include "incls/_gcLocker.cpp.incl"
27
28 volatile jint GC_locker::_jni_lock_count = 0;
29 volatile jint GC_locker::_lock_count = 0;
30 volatile bool GC_locker::_needs_gc = false;
31 volatile bool GC_locker::_doing_gc = false;
32
33 void GC_locker::stall_until_clear() {
34 assert(!JavaThread::current()->in_critical(), "Would deadlock");
35 if (PrintJNIGCStalls && PrintGCDetails) {
36 ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
37 gclog_or_tty->print_cr(
38 "Allocation failed. Thread \"%s\" is stalled by JNI critical section.",
39 JavaThread::current()->name());
40 }
41 MutexLocker ml(JNICritical_lock);
42 // Wait for _needs_gc to be cleared
43 while (GC_locker::needs_gc()) {
44 JNICritical_lock->wait();
45 }
46 }
47
48 void GC_locker::jni_lock_slow() {
49 MutexLocker mu(JNICritical_lock);
50 // Block entering threads if we know at least one thread is in a
51 // JNI critical region and we need a GC.
52 // We check that at least one thread is in a critical region before
53 // blocking because blocked threads are woken up by a thread exiting
54 // a JNI critical region.
55 while ((is_jni_active() && needs_gc()) || _doing_gc) {
56 JNICritical_lock->wait();
57 }
58 jni_lock();
59 }
60
61 void GC_locker::jni_unlock_slow() {
62 MutexLocker mu(JNICritical_lock);
63 jni_unlock();
64 if (needs_gc() && !is_jni_active()) {
65 // We're the last thread out. Cause a GC to occur.
66 // GC will also check is_active, so this check is not
67 // strictly needed. It's added here to make it clear that
68 // the GC will NOT be performed if any other caller
69 // of GC_locker::lock() still needs GC locked.
70 if (!is_active()) {
71 _doing_gc = true;
72 {
73 // Must give up the lock while at a safepoint
74 MutexUnlocker munlock(JNICritical_lock);
75 Universe::heap()->collect(GCCause::_gc_locker);
76 }
77 _doing_gc = false;
78 }
79 clear_needs_gc();
80 JNICritical_lock->notify_all();
81 }
82 }
83
84 // Implementation of No_GC_Verifier
85
86 #ifdef ASSERT
87
88 No_GC_Verifier::No_GC_Verifier(bool verifygc) {
89 _verifygc = verifygc;
90 if (_verifygc) {
91 CollectedHeap* h = Universe::heap();
92 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
93 _old_invocations = h->total_collections();
94 }
95 }
96
97
98 No_GC_Verifier::~No_GC_Verifier() {
99 if (_verifygc) {
100 CollectedHeap* h = Universe::heap();
101 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
102 if (_old_invocations != h->total_collections()) {
103 fatal("collection in a No_GC_Verifier secured function");
104 }
105 }
106 }
107
108 Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {
109 _ngcv = ngcv;
110 if (_ngcv->_verifygc) {
111 // if we were verifying, then make sure that nothing is
112 // wrong before we "pause" verification
113 CollectedHeap* h = Universe::heap();
114 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
115 if (_ngcv->_old_invocations != h->total_collections()) {
116 fatal("collection in a No_GC_Verifier secured function");
117 }
118 }
119 }
120
121
122 Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {
123 if (_ngcv->_verifygc) {
124 // if we were verifying before, then reenable verification
125 CollectedHeap* h = Universe::heap();
126 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
127 _ngcv->_old_invocations = h->total_collections();
128 }
129 }
130
131
132 // JRT_LEAF rules:
133 // A JRT_LEAF method may not interfere with safepointing by
134 // 1) acquiring or blocking on a Mutex or JavaLock - checked
135 // 2) allocating heap memory - checked
136 // 3) executing a VM operation - checked
137 // 4) executing a system call (including malloc) that could block or grab a lock
138 // 5) invoking GC
139 // 6) reaching a safepoint
140 // 7) running too long
141 // Nor may any method it calls.
142 JRT_Leaf_Verifier::JRT_Leaf_Verifier()
143 : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())
144 {
145 }
146
147 JRT_Leaf_Verifier::~JRT_Leaf_Verifier()
148 {
149 }
150
151 bool JRT_Leaf_Verifier::should_verify_GC() {
152 switch (JavaThread::current()->thread_state()) {
153 case _thread_in_Java:
154 // is in a leaf routine, there must be no safepoint.
155 return true;
156 case _thread_in_native:
157 // A native thread is not subject to safepoints.
158 // Even while it is in a leaf routine, GC is ok
159 return false;
160 default:
161 // Leaf routines cannot be called from other contexts.
162 ShouldNotReachHere();
163 return false;
164 }
165 }
166 #endif