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[Bob Chen]

POC:

Set up a socket client with multiple threads, each of the threads establishing a connection to a server. (Not using pooled-socket.)

In each send/recv, we would use wait_for_fd to do one-shot poll, and the underlying method is add_interest.

The error occurs at line 127.

PhotonLibOS/io/epoll.cpp

Lines 114 to 129 in 87d0bae

 virtual int add_interest(Event e) override { 
     if (e.fd < 0) 
         LOG_ERROR_RETURN(EINVAL, -1, "invalid file descriptor ", e.fd); 
     if ((size_t)e.fd >= _inflight_events.size()) 
         _inflight_events.resize(e.fd * 2); 
     auto& entry = _inflight_events[e.fd]; 
     if (e.interests & entry.interests) { 
         if (((e.interests & entry.interests & EVENT_READ) && 
              (entry.reader_data != e.data)) || 
             ((e.interests & entry.interests & EVENT_WRITE) && 
              (entry.writer_data != e.data)) || 
             ((e.interests & entry.interests & EVENT_ERROR) && 
              (entry.error_data != e.data))) { 
             LOG_ERROR_RETURN(EALREADY, -1, "conflicted interest(s)"); 
         } 
     } 

Below is a POC you can verify:

Client: ./net-perf -client -ip 10.144.106.75 -client_thread_num 8
Server: ./net-perf

https://github.com/beef9999/PhotonLibOS/blob/beef9999/poc-conflicted-interest/examples/perf/net-perf.cpp

[Bob Chen]

io_uring engine doesn't have this problem