From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753195AbaBYXoa (ORCPT ); Tue, 25 Feb 2014 18:44:30 -0500 Received: from mail-pd0-f173.google.com ([209.85.192.173]:42791 "EHLO mail-pd0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752072AbaBYXo2 (ORCPT ); Tue, 25 Feb 2014 18:44:28 -0500 Message-ID: <1393371856.2886.2.camel@linux-whg8.site> Subject: Re: [RFC PATCH for-next 2/4] epoll: epoll() syscall declaration From: Nathaniel Yazdani To: Eric Wong Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 25 Feb 2014 15:44:16 -0800 In-Reply-To: <20140225103013.GB9963@dcvr.yhbt.net> References: <1393206162-18151-1-git-send-email-n1ght.4nd.d4y@gmail.com> <1393206162-18151-3-git-send-email-n1ght.4nd.d4y@gmail.com> <20140224053232.GB7056@dcvr.yhbt.net> <20140225103013.GB9963@dcvr.yhbt.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2014-02-25 at 10:30 +0000, Eric Wong wrote: > Nathaniel Yazdani wrote: > > On Sun, Feb 23, 2014 at 9:32 PM, Eric Wong wrote: > > > Nathaniel Yazdani wrote: > > >> +asmlinkage long sys_epoll(int ep, struct epoll __user *in, > > >> + unsigned int inc, struct epoll __user *out, > > >> + unsigned int outc, int timeout); > > > > > > I can understand using the new struct for 'in', but 'out' could just be > > > "struct epoll_event *" like sys_epoll_wait, right? > > > > > >> asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, > > > > Yeah and I went back and forth on that, it just seemed to me that the > > inconsistency could be confusing to others... maybe instead of defining a new > > struct to begin with it might make me sense to just have an 'infd' array of file > > descriptors in addition to an 'in' array of epoll_event struct > > (obviously the length > > of these would be identical). > > I don't think a separate array for in is a good idea, too error prone > and you lose locality. > > For output, some users either end up allocating more memory/retrieve > fewer items with the larger struct for *out. Well having a different struct for input and output would be just as error prone too, plus the file descriptor of a triggered event is highly relevant information.