Hi Arnaldo, Things have gone quiet ;-). What's the current state of this patch? Thanks, Michael On Thu, May 29, 2014 at 4:17 PM, Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx> wrote: > Em Thu, May 29, 2014 at 02:06:04PM +0000, David Laight escreveu: >> From: 'Arnaldo Carvalho de Melo' >> ... >> > > I remember some discussions from an XNET standards meeting (I've forgotten >> > > exactly which errors on which calls were being discussed). >> > > My recollection is that you return success with a partial transfer >> > > count for ANY error that happens after some data has been transferred. >> > > The actual error will be returned when it happens again on the next >> > > system call - Note the AGAIN, not a saved error. > >> > A saved error, for the right entity, in the recvmmsg case, that >> > basically is batching multiple recvmsg syscalls, doesn't sound like a >> > problem, i.e. the idea is to, as much as possible, mimic what multiple >> > recvmsg calls would do, but reduce its in/out kernel (and inside kernel >> > subsystems) overhead. > >> > Perhaps we can have something in between, i.e. for things like EFAULT, >> > we should report straight away, effectively dropping whatever datagrams >> > successfully received in the current batch, do you agree? > >> Not unreasonable - EFAULT shouldn't happen unless the application >> is buggy. > > Ok. > >> > For transient errors the existing mechanism, fixed so that only per >> > socket errors are saved for later, as today, could be kept? > >> I don't think it is ever necessary to save an errno value for the >> next system call at all. >> Just process the next system call and see what happens. > >> If the call returns with less than the maximum number of datagrams >> and with a non-zero timeout left - then the application can infer >> that it was terminated by an abnormal event of some kind. >> This might be a signal. > > Then it could use getsockopt(SO_ERROR) perhaps? I.e. we don't return the > error on the next call, but we provide a way for the app to retrieve the > reason for the smaller than expected batch? > >> I'm not sure if an icmp error on a connected datagram socket could >> generate a 'disconnect'. It might happen if the interface is being >> used for something like SCTP. >> In either case the next call will detect the error. > > - Arnaldo -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
