From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Kerrisk Subject: Re: Problem with semantics? Date: Mon, 27 Aug 2007 17:46:09 +0200 Message-ID: <46D2F1C1.2050606@gmx.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Shay Goikhman , netdev@vger.kernel.org, davem@davemloft.net To: Andi Kleen Return-path: Received: from mail.gmx.net ([213.165.64.20]:37676 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754663AbXH0PsE (ORCPT ); Mon, 27 Aug 2007 11:48:04 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi Andi, Andi Kleen wrote: > Shay Goikhman writes: > >> Dear Linux maintainers, >> >> I'm doing : >> >> setsockopt(s, SO_RCVTIMEO, t1 ); // set time-out >> t1 on socket while block receiving on it >> select(,,, &fd_set_including(s), .., &errs, t2); // block till >> receive or time-out t 2 jointly on a set of sockets >> >> Apparently, I could no find reference on the coupled behavior of the two >> above statements in Linux documentation. >> As I understand the blocking semantics, I would expect that if t1> select should return after t1 with the descriptor 's' in 'errs' if 's' does >> not become readable in the t1 interval. >> >> It is not so in life -- select ignores t1 altogether. >> >> Do you have some enlightening knowledge on the matter? > > RCVTIMEO only applies to recvmsg et.al., similar to SNDTIMEO only > apply to sendmsg etc. But select/poll only report events, they > do not actually send or receive by themselves. > > Michael, perhaps you can clarify that in the manpages I added the following to sockets.7: Timeouts have effect for socket I/O calls (read(2), recv(2), recvfrom(2), recvmsg(2), write(2), send(2), sendto(2), sendmsg(2)); timeouts have no effect for select(2), poll(2), epoll_wait(2), etc. The change will be in man-pages-2.65. Thanks for your note. Cheers, Michael -- Michael Kerrisk maintainer of Linux man pages Sections 2, 3, 4, 5, and 7 Want to help with man page maintenance? Grab the latest tarball at http://www.kernel.org/pub/linux/docs/manpages/ read the HOWTOHELP file and grep the source files for 'FIXME'.