Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753942AbXFUSXw (ORCPT ); Thu, 21 Jun 2007 14:23:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751557AbXFUSXo (ORCPT ); Thu, 21 Jun 2007 14:23:44 -0400 Received: from mail.screens.ru ([213.234.233.54]:46298 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbXFUSXo (ORCPT ); Thu, 21 Jun 2007 14:23:44 -0400 Date: Thu, 21 Jun 2007 22:23:40 +0400 From: Oleg Nesterov To: Linus Torvalds Cc: Benjamin Herrenschmidt , Davide Libenzi , Nicholas Miell , Linux Kernel Mailing List Subject: Re: Fix signalfd interaction with thread-private signals Message-ID: <20070621182340.GA92@tv-sign.ru> References: <1182127391.26853.207.camel@localhost.localdomain> <20070619091452.GA94@tv-sign.ru> <1182254988.26853.334.camel@localhost.localdomain> <20070619140646.GB27343@tv-sign.ru> <1182295473.26853.386.camel@localhost.localdomain> <20070620111415.GA91@tv-sign.ru> <20070621082509.GA88@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 X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1353 Lines: 38 On 06/21, Linus Torvalds wrote: > > On Thu, 21 Jun 2007, Oleg Nesterov wrote: > > > > Yes, force_sig() unblocks and un-ignores the signal. However, unlike group-wide > > signals, thread-specific signals do not convert themselves to SIGKILL on delivery. > > The target thread should dequeue SIGSEGV and then it calls do_group_exit(). > > No it couldn't. > > Why? Because the target thread is the one that *caused* the SIGSEGV in the > first place. It's not going to dequeue *anything*. It's either going to > take the SIGSEGV, Hmm, can't understand. Yes, the target thread is the one that caused the SIGSEGV, it sends the signal to itself. entry.S:ret_from_exception should notice this signal and _dequeue_ it, no? This signal could be stealed by signal(SIG_IGN) which runs after it was delivered. > or it's going to get another SIGSEGV and now it's no > longer masked/handled and it's going to die. Yes sure. As I said, > and the target thread will take page fault again. My point was that it is _possible_ to steal a thread-local SIGSEGV even without signalfd, nothing bad should happen. 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/