Tue, 19 Aug 2014 02:05:49 -0700
8044406: JVM crash with JDK8 (build 1.8.0-b132) with G1 GC
Summary: Fill the last card that has been allocated into with a dummy object
Reviewed-by: tschatzl, mgerdin
1 /*
2 * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
29 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
30 HeapRegion* G1AllocRegion::_dummy_region = NULL;
32 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
33 assert(_dummy_region == NULL, "should be set once");
34 assert(dummy_region != NULL, "pre-condition");
35 assert(dummy_region->free() == 0, "pre-condition");
37 // Make sure that any allocation attempt on this region will fail
38 // and will not trigger any asserts.
39 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
40 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
41 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
42 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
44 _g1h = g1h;
45 _dummy_region = dummy_region;
46 }
48 void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
49 bool bot_updates) {
50 assert(alloc_region != NULL && alloc_region != _dummy_region,
51 "pre-condition");
53 // Other threads might still be trying to allocate using a CAS out
54 // of the region we are trying to retire, as they can do so without
55 // holding the lock. So, we first have to make sure that noone else
56 // can allocate out of it by doing a maximal allocation. Even if our
57 // CAS attempt fails a few times, we'll succeed sooner or later
58 // given that failed CAS attempts mean that the region is getting
59 // closed to being full.
60 size_t free_word_size = alloc_region->free() / HeapWordSize;
62 // This is the minimum free chunk we can turn into a dummy
63 // object. If the free space falls below this, then noone can
64 // allocate in this region anyway (all allocation requests will be
65 // of a size larger than this) so we won't have to perform the dummy
66 // allocation.
67 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
69 while (free_word_size >= min_word_size_to_fill) {
70 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
71 if (dummy != NULL) {
72 // If the allocation was successful we should fill in the space.
73 CollectedHeap::fill_with_object(dummy, free_word_size);
74 alloc_region->set_pre_dummy_top(dummy);
75 break;
76 }
78 free_word_size = alloc_region->free() / HeapWordSize;
79 // It's also possible that someone else beats us to the
80 // allocation and they fill up the region. In that case, we can
81 // just get out of the loop.
82 }
83 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
84 "post-condition");
85 }
87 void G1AllocRegion::retire(bool fill_up) {
88 assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
90 trace("retiring");
91 HeapRegion* alloc_region = _alloc_region;
92 if (alloc_region != _dummy_region) {
93 // We never have to check whether the active region is empty or not,
94 // and potentially free it if it is, given that it's guaranteed that
95 // it will never be empty.
96 assert(!alloc_region->is_empty(),
97 ar_ext_msg(this, "the alloc region should never be empty"));
99 if (fill_up) {
100 fill_up_remaining_space(alloc_region, _bot_updates);
101 }
103 assert(alloc_region->used() >= _used_bytes_before,
104 ar_ext_msg(this, "invariant"));
105 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
106 retire_region(alloc_region, allocated_bytes);
107 _used_bytes_before = 0;
108 _alloc_region = _dummy_region;
109 }
110 trace("retired");
111 }
113 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
114 bool force) {
115 assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
116 assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
118 trace("attempting region allocation");
119 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
120 if (new_alloc_region != NULL) {
121 new_alloc_region->reset_pre_dummy_top();
122 // Need to do this before the allocation
123 _used_bytes_before = new_alloc_region->used();
124 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
125 assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
127 OrderAccess::storestore();
128 // Note that we first perform the allocation and then we store the
129 // region in _alloc_region. This is the reason why an active region
130 // can never be empty.
131 _alloc_region = new_alloc_region;
132 _count += 1;
133 trace("region allocation successful");
134 return result;
135 } else {
136 trace("region allocation failed");
137 return NULL;
138 }
139 ShouldNotReachHere();
140 }
142 void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
143 msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
144 _name, message, _count, BOOL_TO_STR(_bot_updates),
145 p2i(_alloc_region), _used_bytes_before);
146 }
148 void G1AllocRegion::init() {
149 trace("initializing");
150 assert(_alloc_region == NULL && _used_bytes_before == 0,
151 ar_ext_msg(this, "pre-condition"));
152 assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
153 _alloc_region = _dummy_region;
154 _count = 0;
155 trace("initialized");
156 }
158 void G1AllocRegion::set(HeapRegion* alloc_region) {
159 trace("setting");
160 // We explicitly check that the region is not empty to make sure we
161 // maintain the "the alloc region cannot be empty" invariant.
162 assert(alloc_region != NULL && !alloc_region->is_empty(),
163 ar_ext_msg(this, "pre-condition"));
164 assert(_alloc_region == _dummy_region &&
165 _used_bytes_before == 0 && _count == 0,
166 ar_ext_msg(this, "pre-condition"));
168 _used_bytes_before = alloc_region->used();
169 _alloc_region = alloc_region;
170 _count += 1;
171 trace("set");
172 }
174 HeapRegion* G1AllocRegion::release() {
175 trace("releasing");
176 HeapRegion* alloc_region = _alloc_region;
177 retire(false /* fill_up */);
178 assert(_alloc_region == _dummy_region,
179 ar_ext_msg(this, "post-condition of retire()"));
180 _alloc_region = NULL;
181 trace("released");
182 return (alloc_region == _dummy_region) ? NULL : alloc_region;
183 }
185 #if G1_ALLOC_REGION_TRACING
186 void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
187 // All the calls to trace that set either just the size or the size
188 // and the result are considered part of level 2 tracing and are
189 // skipped during level 1 tracing.
190 if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
191 const size_t buffer_length = 128;
192 char hr_buffer[buffer_length];
193 char rest_buffer[buffer_length];
195 HeapRegion* alloc_region = _alloc_region;
196 if (alloc_region == NULL) {
197 jio_snprintf(hr_buffer, buffer_length, "NULL");
198 } else if (alloc_region == _dummy_region) {
199 jio_snprintf(hr_buffer, buffer_length, "DUMMY");
200 } else {
201 jio_snprintf(hr_buffer, buffer_length,
202 HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
203 }
205 if (G1_ALLOC_REGION_TRACING > 1) {
206 if (result != NULL) {
207 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
208 word_size, result);
209 } else if (word_size != 0) {
210 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
211 } else {
212 jio_snprintf(rest_buffer, buffer_length, "");
213 }
214 } else {
215 jio_snprintf(rest_buffer, buffer_length, "");
216 }
218 tty->print_cr("[%s] %u %s : %s %s",
219 _name, _count, hr_buffer, str, rest_buffer);
220 }
221 }
222 #endif // G1_ALLOC_REGION_TRACING
224 G1AllocRegion::G1AllocRegion(const char* name,
225 bool bot_updates)
226 : _name(name), _bot_updates(bot_updates),
227 _alloc_region(NULL), _count(0), _used_bytes_before(0) { }