Em Thu, May 22, 2014 at 04:27:45PM +0200, Michael Kerrisk (man-pages) escreveu: > Hi Arnaldo, > > On 05/21/2014 11:05 PM, Arnaldo Carvalho de Melo wrote: > > Em Mon, May 12, 2014 at 11:34:51AM -0300, Arnaldo Carvalho de Melo escreveu: > >> Em Mon, May 12, 2014 at 12:15:25PM +0200, Michael Kerrisk (man-pages) escreveu: > >>> Hi Arnaldo, > > > >>> Ping! > > > >> I acknowledge the problem, the timeout has to be passed to the > >> underlying ->recvmsg() implementations that should return the time spent > >> waiting for each packet, so that we can accrue that at recvmmsg level. > > > >> We can do either passing an extra timeout parameter to the recvmsg > >> implementations or using some struct sock member to specify that > >> timeout. > > > >> The first approach is intrusive, touches tons of files, so I'll try > >> making it all mostly transparent by hooking into sock_rcvtimeo() > >> somehow. > > > > But after thinking a bit more, looks like we need to do that, please > > take a look at the attached patch to see if it addresses the problem. > > > > Mostly it adds a new timeop to the per protocol recvmsg() > > implementations, that, if not NULL, should be used instead of > > SO_RCVTIMEO. > > > > since the underlying recvmsg implementations already check that timeout, > > return what is remaining, that will then be used in subsequent recvmsg > > calls, at the end we just convert it back to timespec format. > > > > In most cases it is just passed to skb_recv_datagram, that will check > > the pointer, use it and update if not NULL. > > > > Should have no problems, but I only did a boot with a system with this > > patch applied, no problems noticed on a normal desktop session, ssh, > > etc. > > Thanks! I applied this patch against 3.15-rc6. > > recvmmsg() now (mostly) does what I expect: > * it waits until either the timeout expires or vlen messages > have been received > * If no message is received before timeout, it returns -1/EAGAIN. > * If vlen messages are received before the timeout expires, then > the remaining time is returned in timeout. > > One question: in the event that the call is interrupted by a signal > handler, it fails (as expected) with EINTR, but the 'timeout' value is > not updated with the remaining time on the timer. Would it be desirable > to emulate the behavior of select() (and other syscalls) in this > respect, and instead return the remaining time if interrupted by > a signal? I think so, will check how to achieve that! > Cheers, > > Michael > > -- > 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 netdev" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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
