Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754158AbYB1GSP (ORCPT ); Thu, 28 Feb 2008 01:18:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751040AbYB1GR7 (ORCPT ); Thu, 28 Feb 2008 01:17:59 -0500 Received: from x346.tv-sign.ru ([89.108.83.215]:39115 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750695AbYB1GR7 (ORCPT ); Thu, 28 Feb 2008 01:17:59 -0500 Date: Thu, 28 Feb 2008 09:17:23 +0300 From: Oleg Nesterov To: Thomas Gleixner Cc: Pavel Emelyanov , Andrew Morton , Linux Kernel Mailing List , Roland McGrath Subject: Re: [PATCH 3/3] Consolidate send_sigqueue and send_group_sigqueue Message-ID: <20080228061723.GB108@tv-sign.ru> References: <47BEC663.7050904@openvz.org> <20080222144155.GA4349@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2428 Lines: 71 On 02/28, Thomas Gleixner wrote: > > On Fri, 22 Feb 2008, Oleg Nesterov wrote: > > > - > > > - if (unlikely(!list_empty(&q->list))) { > > > - /* > > > - * If an SI_TIMER entry is already queue just increment > > > - * the overrun count. > > > - */ > > > - BUG_ON(q->info.si_code != SI_TIMER); > > > - q->info.si_overrun++; > > > - goto out; > > > - } > > > - /* Short-circuit ignored signals. */ > > > - if (sig_ignored(p, sig)) { > > > - ret = 1; > > > - goto out; > > > - } > > > > send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) > > > > - /* Short-circuit ignored signals. */ > > > - if (sig_ignored(p, sig)) { > > > - ret = 1; > > > - goto out; > > > - } > > > - > > > - if (unlikely(!list_empty(&q->list))) { > > > - /* > > > - * If an SI_TIMER entry is already queue just increment > > > - * the overrun count. Other uses should not try to > > > - * send the signal multiple times. > > > - */ > > > - BUG_ON(q->info.si_code != SI_TIMER); > > > - q->info.si_overrun++; > > > - goto out; > > > - } > > > > Personally, I think this change is very good. But send_sigqueue() and > > send_group_sigqueue() have a very subtle difference which I was never > > able to understand. > > > > Let's suppose that sigqueue is already queued, and the signal is ignored > > (the latter means we should re-schedule cpu timer or handle overrruns). > > In that case send_sigqueue() returns 0, but send_group_sigqueue() returns 1. > > > > I think this is not the problem (in fact, I think this patch makes the > > behaviour more correct), but I hope Thomas can take a look and confirm. > > It should not change anything. We should never have a signal enqueued > when it's ignored anyway. Well, it _is_ possible. Suppose that the signal is both ignored and blocked. Now, if the task unblocks the signal, it could be ignored, queued, and sig_ignored() == T. But yes, I think you are right, this can't change anything. I just wanted to be sure there is no subtle reason to prefer one way or another. > Roland, any insight why this is different aside of a copy and paste > error ? I guess this was the reason for the difference. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/