From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751917AbXCSTM2 (ORCPT ); Mon, 19 Mar 2007 15:12:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751199AbXCSTM2 (ORCPT ); Mon, 19 Mar 2007 15:12:28 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:50844 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751917AbXCSTM2 (ORCPT ); Mon, 19 Mar 2007 15:12:28 -0400 X-AuthUser: davidel@xmailserver.org Date: Mon, 19 Mar 2007 12:11:01 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: "Eric W. Biederman" cc: Linux Kernel Mailing List , Andrew Morton , Linus Torvalds , Oleg Nesterov Subject: Re: [patch 2/13] signal/timer/event fds v6 - signalfd core ... In-Reply-To: Message-ID: References: X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Mar 2007, Eric W. Biederman wrote: > Davide Libenzi writes: > > > On Mon, 19 Mar 2007, Eric W. Biederman wrote: > > > >> Davide Libenzi writes: > >> > >> > struct signalfd_siginfo { > >> > __u32 signo; /* si_signo */ > >> > __s32 err; /* si_errno */ > >> > __s32 code; /* si_code */ > >> > __u32 pid; /* si_pid */ > >> > __u32 uid; /* si_uid */ > >> > __s32 fd; /* si_fd */ > >> > __u32 tid; /* si_fd */ > >> > __u32 band; /* si_band */ > >> > __u32 overrun; /* si_overrun */ > >> > __u32 trapno; /* si_trapno */ > >> > __s32 status; /* si_status */ > >> > __s32 svint; /* si_int */ > >> > __u64 svptr; /* si_ptr */ > >> > __u64 utime; /* si_utime */ > >> > __u64 stime; /* si_stime */ > >> > __u64 addr; /* si_addr */ > >> > }; > >> > >> Shouldn't we pad this to 128 bytes like we do siginfo in case there are > >> more fields we need to include, or we need to extend the size of some > >> field? > > > > Yes, I guess we can. > > I'm just a little paranoid about ABI's. There is always something > that crops up. And while we can probably cope by simply having another > version of the signalfd or whatever your syscall is, but having to do > that at the first sign of trouble sucks. Especially since we would have > to maintain two versions indefinitely. Ok, I added the padding to 128 bytes to the struct. > >> I think you want to use a struct pid *pid instead of a pointer to the > >> task struct here. It is slightly less efficient (one more > >> dereference) but it means that we won't pin the task struct in memory > >> indefinitely. Pinning the task_struct like this makes for a very > >> interesting way to get around the limits on the number of processes a > >> user can have. > > > > Hmm, when the task is detached from the sighand, we get a notify, so I > > could do a put from there. This would avoid the extra de-reference. I need > > to verify locking though ... > > Ok. That sounds more efficient than playing with struct pid pointers, > if it works. I'm looking into this right now ... - Davide