160
161 void MutableSpace::set_top_for_allocations(HeapWord* v) {
162 mangler()->set_top_for_allocations(v);
163 }
164
165 void MutableSpace::set_top_for_allocations() {
166 mangler()->set_top_for_allocations(top());
167 }
168 #endif
169
170 // This version requires locking. */
171 HeapWord* MutableSpace::allocate(size_t size) {
172 assert(Heap_lock->owned_by_self() ||
173 (SafepointSynchronize::is_at_safepoint() &&
174 Thread::current()->is_VM_thread()),
175 "not locked");
176 HeapWord* obj = top();
177 if (pointer_delta(end(), obj) >= size) {
178 HeapWord* new_top = obj + size;
179 set_top(new_top);
180 assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
181 "checking alignment");
182 return obj;
183 } else {
184 return NULL;
185 }
186 }
187
188 // This version is lock-free.
189 HeapWord* MutableSpace::cas_allocate(size_t size) {
190 do {
191 HeapWord* obj = top();
192 if (pointer_delta(end(), obj) >= size) {
193 HeapWord* new_top = obj + size;
194 HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
195 // result can be one of two:
196 // the old top value: the exchange succeeded
197 // otherwise: the new value of the top is returned.
198 if (result != obj) {
199 continue; // another thread beat us to the allocation, try again
200 }
201 assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
202 "checking alignment");
203 return obj;
204 } else {
205 return NULL;
206 }
207 } while (true);
208 }
209
210 // Try to deallocate previous allocation. Returns true upon success.
211 bool MutableSpace::cas_deallocate(HeapWord *obj, size_t size) {
212 HeapWord* expected_top = obj + size;
213 return (HeapWord*)Atomic::cmpxchg_ptr(obj, top_addr(), expected_top) == expected_top;
214 }
215
216 void MutableSpace::oop_iterate_no_header(OopClosure* cl) {
217 HeapWord* obj_addr = bottom();
218 HeapWord* t = top();
219 // Could call objects iterate, but this is easier.
220 while (obj_addr < t) {
221 obj_addr += oop(obj_addr)->oop_iterate_no_header(cl);
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160
161 void MutableSpace::set_top_for_allocations(HeapWord* v) {
162 mangler()->set_top_for_allocations(v);
163 }
164
165 void MutableSpace::set_top_for_allocations() {
166 mangler()->set_top_for_allocations(top());
167 }
168 #endif
169
170 // This version requires locking. */
171 HeapWord* MutableSpace::allocate(size_t size) {
172 assert(Heap_lock->owned_by_self() ||
173 (SafepointSynchronize::is_at_safepoint() &&
174 Thread::current()->is_VM_thread()),
175 "not locked");
176 HeapWord* obj = top();
177 if (pointer_delta(end(), obj) >= size) {
178 HeapWord* new_top = obj + size;
179 set_top(new_top);
180 assert(is_ptr_object_aligned(obj) && is_ptr_object_aligned(new_top),
181 "checking alignment");
182 return obj;
183 } else {
184 return NULL;
185 }
186 }
187
188 // This version is lock-free.
189 HeapWord* MutableSpace::cas_allocate(size_t size) {
190 do {
191 HeapWord* obj = top();
192 if (pointer_delta(end(), obj) >= size) {
193 HeapWord* new_top = obj + size;
194 HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
195 // result can be one of two:
196 // the old top value: the exchange succeeded
197 // otherwise: the new value of the top is returned.
198 if (result != obj) {
199 continue; // another thread beat us to the allocation, try again
200 }
201 assert(is_ptr_object_aligned(obj) && is_ptr_object_aligned(new_top),
202 "checking alignment");
203 return obj;
204 } else {
205 return NULL;
206 }
207 } while (true);
208 }
209
210 // Try to deallocate previous allocation. Returns true upon success.
211 bool MutableSpace::cas_deallocate(HeapWord *obj, size_t size) {
212 HeapWord* expected_top = obj + size;
213 return (HeapWord*)Atomic::cmpxchg_ptr(obj, top_addr(), expected_top) == expected_top;
214 }
215
216 void MutableSpace::oop_iterate_no_header(OopClosure* cl) {
217 HeapWord* obj_addr = bottom();
218 HeapWord* t = top();
219 // Could call objects iterate, but this is easier.
220 while (obj_addr < t) {
221 obj_addr += oop(obj_addr)->oop_iterate_no_header(cl);
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