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This plays the role of the >> STATUS_PIPE_IS_CLOSED macro in the pipe implementation. > > I don't see how to do that. The code is written in a way not requiring > to keep track of stuff at runtime. All shared info is part of the mmap > so far. We don't know if any other mqd_t descriptor is open at the time, > it's not even a descriptor in the usual sense, just a pointer to a private > malloc'ed area. Keeping track of open descriptors requires another > shared mem region at runtime. OK, then I think I can handle this in the AF_UNIX shared memory. Each socket can keep track of its own number of open (socket) descriptors, and then it can send a shutdown message to its peer when the last one is about to close. The sendmsg code will have to be tweaked to repeatedly check for shutdown messages. Ken