JosiahWI commented on code in PR #13170:
URL: https://github.com/apache/trafficserver/pull/13170#discussion_r3260649356
##########
src/tscore/ink_queue.cc:
##########
@@ -519,115 +576,127 @@ ink_atomiclist_init(InkAtomicList *l, const char *name,
uint32_t offset_to_next)
{
l->name = name;
l->offset = offset_to_next;
- SET_FREELIST_POINTER_VERSION(l->head, FROM_PTR(0), 0);
+ head_p empty_head;
+ SET_FREELIST_POINTER_VERSION(empty_head, FROM_PTR(nullptr), 0);
+ l->head.store(empty_head);
}
void *
ink_atomiclist_pop(InkAtomicList *l)
{
head_p item;
head_p next;
- int result = 0;
+ bool result = 0;
+
+ std::lock_guard guard{l->m};
+
+ item = l->head.load();
do {
- INK_QUEUE_LD(item, l->head);
if (TO_PTR(FREELIST_POINTER(item)) == nullptr) {
return nullptr;
}
- SET_FREELIST_POINTER_VERSION(next,
*ADDRESS_OF_NEXT(TO_PTR(FREELIST_POINTER(item)), l->offset),
FREELIST_VERSION(item) + 1);
- result = ink_atomic_cas(&l->head.data, item.data, next.data);
- } while (result == 0);
- {
- void *ret = TO_PTR(FREELIST_POINTER(item));
- *ADDRESS_OF_NEXT(ret, l->offset) = nullptr;
- return ret;
- }
+ head_p *next_ptr = reinterpret_cast<head_p *>(reinterpret_cast<unsigned
char *>(TO_PTR(FREELIST_POINTER(item))) + l->offset);
+ SET_FREELIST_POINTER_VERSION(next, FREELIST_POINTER(*next_ptr),
FREELIST_VERSION(item) + 1);
+ result = l->head.compare_exchange_weak(item, next);
+ } while (result == false);
+
+ head_p *ret = reinterpret_cast<head_p *>(reinterpret_cast<unsigned char
*>(TO_PTR(FREELIST_POINTER(item))) + l->offset);
+ SET_FREELIST_POINTER_VERSION(*ret, nullptr, 0);
+ return ret;
}
void *
ink_atomiclist_popall(InkAtomicList *l)
{
head_p item;
head_p next;
- int result = 0;
+ bool result = false;
+
+ item = l->head.load();
do {
- INK_QUEUE_LD(item, l->head);
if (TO_PTR(FREELIST_POINTER(item)) == nullptr) {
return nullptr;
}
SET_FREELIST_POINTER_VERSION(next, FROM_PTR(nullptr),
FREELIST_VERSION(item) + 1);
- result = ink_atomic_cas(&l->head.data, item.data, next.data);
- } while (result == 0);
- {
- void *ret = TO_PTR(FREELIST_POINTER(item));
- void *e = ret;
- /* fixup forward pointers */
- while (e) {
- void *n = TO_PTR(*ADDRESS_OF_NEXT(e, l->offset));
- *ADDRESS_OF_NEXT(e, l->offset) = n;
- e = n;
- }
- return ret;
+ result = l->head.compare_exchange_weak(item, next);
+ } while (result == false);
+
+ void *ret = TO_PTR(FREELIST_POINTER(item));
+ void *e = ret;
+ /* fixup forward pointers */
+ while (e) {
+ head_p *e_ = to_head_p(e, l->offset);
+ void *n = TO_PTR(FREELIST_POINTER(*e_));
+ SET_FREELIST_POINTER_VERSION(*e_, n, FREELIST_VERSION(*e_));
+ e = n;
Review Comment:
If the offset is applied before checking for nullptr, it is possible to pass
the tscore tests but fail a bunch of other unit tests (event system and cache
tests).
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