Concurrent class unloading
107
108 // Set the package as exported to all unnamed modules unless the package is
109 // already unqualifiedly exported.
110 void PackageEntry::set_is_exported_allUnnamed() {
111 if (module()->is_open()) {
112 // No-op for open modules since all packages are unqualifiedly exported
113 return;
114 }
115
116 MutexLocker m1(Module_lock);
117 if (!is_unqual_exported()) {
118 _export_flags = PKG_EXP_ALLUNNAMED;
119 }
120 }
121
122 // Remove dead module entries within the package's exported list. Note that
123 // if all of the modules on the _qualified_exports get purged the list does not
124 // get deleted. This prevents the package from illegally transitioning from
125 // exported to non-exported.
126 void PackageEntry::purge_qualified_exports() {
127 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
128 if (_must_walk_exports &&
129 _qualified_exports != NULL &&
130 !_qualified_exports->is_empty()) {
131 ModuleEntry* pkg_module = module();
132
133 // This package's _must_walk_exports flag will be reset based
134 // on the remaining live modules on the exports list.
135 _must_walk_exports = false;
136
137 if (log_is_enabled(Trace, module)) {
138 ResourceMark rm;
139 assert(name() != NULL, "PackageEntry without a valid name");
140 ModuleEntry* pkg_mod = module();
141 log_trace(module)("PackageEntry::purge_qualified_exports(): package %s defined in module %s, exports list being walked",
142 name()->as_C_string(),
143 (pkg_mod == NULL || pkg_mod->name() == NULL) ? UNNAMED_MODULE : pkg_mod->name()->as_C_string());
144 }
145
146 // Go backwards because this removes entries that are dead.
147 int len = _qualified_exports->length();
148 for (int idx = len - 1; idx >= 0; idx--) {
149 ModuleEntry* module_idx = _qualified_exports->at(idx);
150 ClassLoaderData* cld_idx = module_idx->loader_data();
151 if (cld_idx->is_unloading()) {
152 _qualified_exports->delete_at(idx);
153 } else {
154 // Update the need to walk this package's exports based on live modules
155 set_export_walk_required(cld_idx);
156 }
157 }
158 }
159 }
160
161 void PackageEntry::delete_qualified_exports() {
162 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
163 if (_qualified_exports != NULL) {
164 delete _qualified_exports;
165 }
166 _qualified_exports = NULL;
167 }
168
169 PackageEntryTable::PackageEntryTable(int table_size)
170 : Hashtable<Symbol*, mtModule>(table_size, sizeof(PackageEntry))
171 {
172 }
173
174 PackageEntryTable::~PackageEntryTable() {
175 // Walk through all buckets and all entries in each bucket,
176 // freeing each entry.
177 for (int i = 0; i < table_size(); ++i) {
178 for (PackageEntry* p = bucket(i); p != NULL;) {
179 PackageEntry* to_remove = p;
180 // read next before freeing.
181 p = p->next();
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107
108 // Set the package as exported to all unnamed modules unless the package is
109 // already unqualifiedly exported.
110 void PackageEntry::set_is_exported_allUnnamed() {
111 if (module()->is_open()) {
112 // No-op for open modules since all packages are unqualifiedly exported
113 return;
114 }
115
116 MutexLocker m1(Module_lock);
117 if (!is_unqual_exported()) {
118 _export_flags = PKG_EXP_ALLUNNAMED;
119 }
120 }
121
122 // Remove dead module entries within the package's exported list. Note that
123 // if all of the modules on the _qualified_exports get purged the list does not
124 // get deleted. This prevents the package from illegally transitioning from
125 // exported to non-exported.
126 void PackageEntry::purge_qualified_exports() {
127 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
128 if (_must_walk_exports &&
129 _qualified_exports != NULL &&
130 !_qualified_exports->is_empty()) {
131 ModuleEntry* pkg_module = module();
132
133 // This package's _must_walk_exports flag will be reset based
134 // on the remaining live modules on the exports list.
135 _must_walk_exports = false;
136
137 if (log_is_enabled(Trace, module)) {
138 ResourceMark rm;
139 assert(name() != NULL, "PackageEntry without a valid name");
140 ModuleEntry* pkg_mod = module();
141 log_trace(module)("PackageEntry::purge_qualified_exports(): package %s defined in module %s, exports list being walked",
142 name()->as_C_string(),
143 (pkg_mod == NULL || pkg_mod->name() == NULL) ? UNNAMED_MODULE : pkg_mod->name()->as_C_string());
144 }
145
146 // Go backwards because this removes entries that are dead.
147 int len = _qualified_exports->length();
148 for (int idx = len - 1; idx >= 0; idx--) {
149 ModuleEntry* module_idx = _qualified_exports->at(idx);
150 ClassLoaderData* cld_idx = module_idx->loader_data();
151 if (cld_idx->is_unloading()) {
152 _qualified_exports->delete_at(idx);
153 } else {
154 // Update the need to walk this package's exports based on live modules
155 set_export_walk_required(cld_idx);
156 }
157 }
158 }
159 }
160
161 void PackageEntry::delete_qualified_exports() {
162 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
163 if (_qualified_exports != NULL) {
164 delete _qualified_exports;
165 }
166 _qualified_exports = NULL;
167 }
168
169 PackageEntryTable::PackageEntryTable(int table_size)
170 : Hashtable<Symbol*, mtModule>(table_size, sizeof(PackageEntry))
171 {
172 }
173
174 PackageEntryTable::~PackageEntryTable() {
175 // Walk through all buckets and all entries in each bucket,
176 // freeing each entry.
177 for (int i = 0; i < table_size(); ++i) {
178 for (PackageEntry* p = bucket(i); p != NULL;) {
179 PackageEntry* to_remove = p;
180 // read next before freeing.
181 p = p->next();
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210 void PackageEntryTable::add_entry(int index, PackageEntry* new_entry) {
211 assert(Module_lock->owned_by_self(), "should have the Module_lock");
212 Hashtable<Symbol*, mtModule>::add_entry(index, (HashtableEntry<Symbol*, mtModule>*)new_entry);
213 }
214
215 // Create package in loader's package entry table and return the entry.
216 // If entry already exists, return null. Assume Module lock was taken by caller.
217 PackageEntry* PackageEntryTable::locked_create_entry_or_null(Symbol* name, ModuleEntry* module) {
218 assert(Module_lock->owned_by_self(), "should have the Module_lock");
219 // Check if package already exists. Return NULL if it does.
220 if (lookup_only(name) != NULL) {
221 return NULL;
222 } else {
223 PackageEntry* entry = new_entry(compute_hash(name), name, module);
224 add_entry(index_for(name), entry);
225 return entry;
226 }
227 }
228
229 PackageEntry* PackageEntryTable::lookup(Symbol* name, ModuleEntry* module) {
230 PackageEntry* p = lookup_only(name);
231 if (p != NULL) {
232 return p;
233 } else {
234 // If not found, add to table. Grab the PackageEntryTable lock first.
235 MutexLocker ml(Module_lock);
236
237 // Since look-up was done lock-free, we need to check if another thread beat
238 // us in the race to insert the package.
239 PackageEntry* test = lookup_only(name);
240 if (test != NULL) {
241 // A race occurred and another thread introduced the package.
242 return test;
243 } else {
244 assert(module != NULL, "module should never be null");
245 PackageEntry* entry = new_entry(compute_hash(name), name, module);
246 add_entry(index_for(name), entry);
247 return entry;
248 }
249 }
250 }
251
252 PackageEntry* PackageEntryTable::lookup_only(Symbol* name) {
253 int index = index_for(name);
254 for (PackageEntry* p = bucket(index); p != NULL; p = p->next()) {
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210 void PackageEntryTable::add_entry(int index, PackageEntry* new_entry) {
211 assert(Module_lock->owned_by_self(), "should have the Module_lock");
212 Hashtable<Symbol*, mtModule>::add_entry(index, (HashtableEntry<Symbol*, mtModule>*)new_entry);
213 }
214
215 // Create package in loader's package entry table and return the entry.
216 // If entry already exists, return null. Assume Module lock was taken by caller.
217 PackageEntry* PackageEntryTable::locked_create_entry_or_null(Symbol* name, ModuleEntry* module) {
218 assert(Module_lock->owned_by_self(), "should have the Module_lock");
219 // Check if package already exists. Return NULL if it does.
220 if (lookup_only(name) != NULL) {
221 return NULL;
222 } else {
223 PackageEntry* entry = new_entry(compute_hash(name), name, module);
224 add_entry(index_for(name), entry);
225 return entry;
226 }
227 }
228
229 PackageEntry* PackageEntryTable::lookup(Symbol* name, ModuleEntry* module) {
230 // If not found, add to table. Grab the PackageEntryTable lock first.
231 MutexLocker ml(Module_lock);
232 PackageEntry* p = lookup_only(name);
233 if (p != NULL) {
234 return p;
235 } else {
236
237 // Since look-up was done lock-free, we need to check if another thread beat
238 // us in the race to insert the package.
239 PackageEntry* test = lookup_only(name);
240 if (test != NULL) {
241 // A race occurred and another thread introduced the package.
242 return test;
243 } else {
244 assert(module != NULL, "module should never be null");
245 PackageEntry* entry = new_entry(compute_hash(name), name, module);
246 add_entry(index_for(name), entry);
247 return entry;
248 }
249 }
250 }
251
252 PackageEntry* PackageEntryTable::lookup_only(Symbol* name) {
253 int index = index_for(name);
254 for (PackageEntry* p = bucket(index); p != NULL; p = p->next()) {
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278 }
279 }
280
281 }
282
283 // iteration of qualified exports
284 void PackageEntry::package_exports_do(ModuleClosure* f) {
285 assert_locked_or_safepoint(Module_lock);
286 assert(f != NULL, "invariant");
287
288 if (has_qual_exports_list()) {
289 int qe_len = _qualified_exports->length();
290
291 for (int i = 0; i < qe_len; ++i) {
292 f->do_module(_qualified_exports->at(i));
293 }
294 }
295 }
296
297 bool PackageEntry::exported_pending_delete() const {
298 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
299 return (is_unqual_exported() && _qualified_exports != NULL);
300 }
301
302 // Remove dead entries from all packages' exported list
303 void PackageEntryTable::purge_all_package_exports() {
304 assert_locked_or_safepoint(Module_lock);
305 for (int i = 0; i < table_size(); i++) {
306 for (PackageEntry* entry = bucket(i);
307 entry != NULL;
308 entry = entry->next()) {
309 if (entry->exported_pending_delete()) {
310 // exported list is pending deletion due to a transition
311 // from qualified to unqualified
312 entry->delete_qualified_exports();
313 } else if (entry->is_qual_exported()) {
314 entry->purge_qualified_exports();
315 }
316 }
317 }
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278 }
279 }
280
281 }
282
283 // iteration of qualified exports
284 void PackageEntry::package_exports_do(ModuleClosure* f) {
285 assert_locked_or_safepoint(Module_lock);
286 assert(f != NULL, "invariant");
287
288 if (has_qual_exports_list()) {
289 int qe_len = _qualified_exports->length();
290
291 for (int i = 0; i < qe_len; ++i) {
292 f->do_module(_qualified_exports->at(i));
293 }
294 }
295 }
296
297 bool PackageEntry::exported_pending_delete() const {
298 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
299 return (is_unqual_exported() && _qualified_exports != NULL);
300 }
301
302 // Remove dead entries from all packages' exported list
303 void PackageEntryTable::purge_all_package_exports() {
304 assert_locked_or_safepoint(Module_lock);
305 for (int i = 0; i < table_size(); i++) {
306 for (PackageEntry* entry = bucket(i);
307 entry != NULL;
308 entry = entry->next()) {
309 if (entry->exported_pending_delete()) {
310 // exported list is pending deletion due to a transition
311 // from qualified to unqualified
312 entry->delete_qualified_exports();
313 } else if (entry->is_qual_exported()) {
314 entry->purge_qualified_exports();
315 }
316 }
317 }
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