Hi Michael, On 01/20/2015 09:09 AM, Michael Kerrisk (man-pages) wrote: > On 11/30/2014 06:23 PM, Florian Weimer wrote: >> * David Herrmann: >> >>> On Sun, Nov 30, 2014 at 10:02 AM, Florian Weimer <fw@xxxxxxxxxxxxx> wrote: >>>> * Greg Kroah-Hartman: >>>> >>>>> +7.4 Receiving messages >> >>>> What happens if this is not possible because the file descriptor limit >>>> of the processes would be exceeded? EMFILE, and the message will not >>>> be received? >>> >>> The message is returned without installing the FDs. This is signaled >>> by EMFILE, but a valid pool offset. >> >> Oh. This is really surprising, so it needs documentation. But it's >> probably better than the alternative (return EMFILE and leave the >> message stuck, so that you receive it immediately again—this behavior >> makes non-blocking accept rather difficult to use correctly). > > So, was this point in the end explicitly documented? I not > obvious that it is documented in the revised kdbus.txt that > Greg K-H sent out 4 days ago. No, we've revisited this point and changed the kernel behavior again in v3. We're no longer returning -EMFILE in this case, but rather set KDBUS_RECV_RETURN_INCOMPLETE_FDS in a new field in the receive ioctl struct called 'return_flags'. We believe that's a nicer way of signaling specific errors. The message will carry -1 for all FDs that failed to get installed, so the user can actually see which one is missing. That's also documented in kdbus.txt, but we missed putting it into the Changelog - sorry for that. Hope this helps, Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
