On 14/11/2019 16.09, Jens Axboe wrote: > On 11/14/19 7:12 AM, Rasmus Villemoes wrote: >> So, I can't really think of anybody that might be relying on inheriting >> a signalfd instead of just setting it up in the child, but changing the >> semantics of it now seems rather dangerous. Also, I _can_ imagine >> threads in a process sharing a signalfd (initial thread sets it up and >> blocks the signals, all threads subsequently use that same fd), and for >> that case it would be wrong for one thread to dequeue signals directed >> at the initial thread. Plus the lifetime problems. > > What if we just made it specific SFD_CLOEXEC? O_CLOEXEC can be set and removed afterwards. Sure, we're far into "nobody does that" land, but having signalfd() have wildly different semantics based on whether it was initially created with O_CLOEXEC seems rather dubious. I don't want to break > existing applications, even if the use case is nonsensical, but it is > important to allow signalfd to be properly used with use cases that are > already in the kernel (aio with IOCB_CMD_POLL, io_uring with > IORING_OP_POLL_ADD). Alternatively, if need be, we could add a specific > SFD_ flag for this. Yeah, if you want another signalfd flavour, adding it via a new SFD_ flag seems the way to go. Though I can't imagine the resulting code would be very pretty. Rasmus
