From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760805Ab3BISZs (ORCPT ); Sat, 9 Feb 2013 13:25:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50159 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760778Ab3BISZq (ORCPT ); Sat, 9 Feb 2013 13:25:46 -0500 Date: Sat, 9 Feb 2013 19:22:39 +0100 From: Oleg Nesterov To: "Michael Kerrisk (man-pages)" Cc: Andrey Wagin , linux-kernel@vger.kernel.org, criu@openvz.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Alexander Viro , "Paul E. McKenney" , David Howells , Dave Jones , Pavel Emelyanov , Cyrill Gorcunov Subject: Re: [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2) Message-ID: <20130209182239.GA9947@redhat.com> References: <1358849741-9611-4-git-send-email-avagin@openvz.org> <1359486181-29088-1-git-send-email-avagin@openvz.org> <20130207173447.GA5888@redhat.com> <20130208191056.GA13674@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/08, Michael Kerrisk (man-pages) wrote: > > On Fri, Feb 8, 2013 at 8:10 PM, Oleg Nesterov wrote: > > > > Well. I do not know. Up to you and Michael. > > > > But honestly, I can't say this all looks really nice. And why do we > > need SIGNALFD_PEEK then? > > It surely is no beauty. The hope is at least to make it less ugly than it was. This is subjective, but I am not sure about "less" ;) Yes, we avoid the magic offsets, but we add SFD_SHARED/PER_THREAD which need to change dequeue_signal plus other complications. And for what? > > Seriously, perhaps we should simply add signalfd_fops->ioctl() for PEEK. > > Or add PTRACE_{PEEK,POKE}_SIGNAL which looks even logical and useful... > > And much simpler/straightforward. > > > > But I am not going to argue. > > I suppose I had wondered along similar lines, but in a slightly > different direction: would the use of a /proc interface to get the > queued signals make some sense? (Can't resist sorry... yes we need /proc/pid/cr or /dev/cr or whatever which dumps almost everything c/r needs without need to add a lot of cr code everywhere). Perhaps, but I am not sure about the textual representation. And to me, the best solution is the simplest solution. Please look at the patch below. It is trivial. And we can also drop the SFD_RAW patch in -mm. Oleg. --- x/kernel/ptrace.c +++ x/kernel/ptrace.c @@ -618,6 +618,35 @@ static int ptrace_setsiginfo(struct task return error; } +static int ptrace_peek_signal(struct task_struct *child, + unsigned long addr, siginfo_t __user *uinfo) +{ + siginfo_t info; + struct sigpending *pending; + int ret = -ESOMETHING; + + pending = &child->pending; + if (addr & PTRACE_PEEK_SHARED) { + addr &= ~PTRACE_PEEK_SHARED; + pending = &child->signal->shared_pending; + } + + spin_lock_irq(&child->sighand->siglock); + list_for_each_entry(q, &pending->list, list) { + if (!addr--) { + copy_siginfo(info, &q->info); + ret = 0; + break; + } + } + spin_lock_irq(&child->sighand->siglock); + + if (!ret) + ret = copy_siginfo_to_user(uinfo, info); + if (!ret) + ret = __put_user(info, si_code); + return ret; +} #ifdef PTRACE_SINGLESTEP #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP) @@ -742,6 +771,10 @@ int ptrace_request(struct task_struct *c ret = put_user(child->ptrace_message, datalp); break; + case PTRACE_PEEKSIGNAL: + ret = ptrace_peek_signal(child, addr, datavp); + break; + case PTRACE_GETSIGINFO: ret = ptrace_getsiginfo(child, &siginfo); if (!ret)