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 -- 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
