bneradt commented on code in PR #12874:
URL: https://github.com/apache/trafficserver/pull/12874#discussion_r2790783156
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src/iocore/net/P_NetAccept.h:
##########
@@ -60,21 +61,30 @@ AcceptFunction net_accept;
class UnixNetVConnection;
-// TODO fix race between cancel accept and call back
struct NetAcceptAction : public Action, public RefCountObjInHeap {
- Server *server;
+ std::atomic<Server *> server{nullptr};
- void
- cancel(Continuation *cont = nullptr) override
+ NetAcceptAction(Continuation *cont, Server *s)
{
- Action::cancel(cont);
- server->close();
+ continuation = cont;
+ if (cont != nullptr) {
+ mutex = cont->mutex;
+ }
+ server.store(s, std::memory_order_release);
}
- Continuation *
- operator=(Continuation *acont)
+ void
+ cancel(Continuation *cont = nullptr) override
{
- return Action::operator=(acont);
+ // Use atomic exchange so only one thread closes the server, preventing
+ // use-after-free races between cancel() and acceptEvent() cleanup.
+ Server *s = server.exchange(nullptr, std::memory_order_acq_rel);
+ if (s != nullptr) {
+ s->close();
+ }
+ if (!cancelled) {
+ Action::cancel(cont);
+ }
Review Comment:
This `!canceled` check is the only change made on top of the reverted #12803
PR. That should hopefully address the double-cancel issue (in addition to
addressing the use after free issue, which the rest of the patch intends to
fix).
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