On 8/27/25 7:39 AM, Lauri Vasama wrote: > For a user mode library to avoid generating SIGPIPE signals (e.g. > because this behaviour is not portable across operating systems) is > cumbersome. It is generally bad form to change the process-wide signal > mask in a library, so a local solution is needed instead. > > For I/O performed directly using system calls (synchronous or readiness > based asynchronous) this currently involves applying a thread-specific > signal mask before the operation and reverting it afterwards. This can be > avoided when it is known that the file descriptor refers to neither a > pipe nor a socket, but a conservative implementation must always apply > the mask. This incurs the cost of two additional system calls. In the > case of sockets, the existing MSG_NOSIGNAL flag can be used with send. > > For asynchronous I/O performed using io_uring, currently the only option > (apart from MSG_NOSIGNAL for sockets), is to mask SIGPIPE entirely in the > call to io_uring_enter. Thankfully io_uring_enter takes a signal mask, so > only a single syscall is needed. However, copying the signal mask on > every call incurs a non-zero performance penalty. Furthermore, this mask > applies to all completions, meaning that if the non-signaling behaviour > is desired only for some subset of operations, the desired signals must > be raised manually from user-mode depending on the completed operation. > > Add RWF_NOSIGNAL flag for pwritev2. This flag prevents the SIGPIPE signal > from being raised when writing on disconnected pipes or sockets. The flag > is handled directly by the pipe filesystem and converted to the existing > MSG_NOSIGNAL flag for sockets. LGTM, only curiosity is why this hasn't been added before. Reviewed-by: Jens Axboe <axboe@xxxxxxxxx> -- Jens Axboe
