Hey, On Tue, Jun 19, 2018 at 15:30, Simon McVittie wrote: On Tue, 19 Jun 2018 at 12:32:19 +0000, mag...@minimum.se (mailto:mag...@minimum.se) wrote: The system is on a quite old kernel (3.18.44) ... At this point, things go wrong when recvmsg() is called on bus->input_fd with flags MSG_DONTWAIT|MSG_NOSIGNAL| MSG_CMSG_CLOEXEC. This syscall returns -22 (Invalid argument) which propagates all the way up to the user.
(I hate the way kernel/syscall/libc error-reporting isn't accompanied by a human-readable message that could tell you *which* argument is invalid... compare with GLib/D-Bus errors) MSG_NOSIGNAL is meaningless for recvmsg() so it's possible that your older kernel doesn't allow it, but newer kernels allow and ignore it? sd-bus should probably only use that flag for sendmsg() and the rest of the send(2) family. You are right, if I remove the MSG_NOSIGNAL flag to recvmsg() everything works (systemd-logind, busctl etc). I was unable to locate the place in my kernel code where it actually rejects MSG_NOSIGNAL for recvmsg(), but I think your theory is sane: 3.18.44 rejects it, newer kernels ignore it. I can send a patch that removes use of MSG_NOSIGNAL in recvmsg() if you are willing to accept it. I think there should be no side effects for users of newer kernels. smcv _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org (mailto:systemd-devel@lists.freedesktop.org) https://lists.freedesktop.org/mailman/listinfo/systemd-devel (https://lists.freedesktop.org/mailman/listinfo/systemd-devel)
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