On 11/14/19 8:19 AM, Rasmus Villemoes wrote: > 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. Well, it's currently _broken_ for the listed in-kernel use cases, so I think making it work is the first priority here. -- Jens Axboe
