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src/share/vm/gc/parallel/mutableSpace.cpp

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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);




 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(obj) && is_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_object_aligned(obj) && is_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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