Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758139AbXFSXY5 (ORCPT ); Tue, 19 Jun 2007 19:24:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754512AbXFSXYu (ORCPT ); Tue, 19 Jun 2007 19:24:50 -0400 Received: from gate.crashing.org ([63.228.1.57]:36071 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754393AbXFSXYu (ORCPT ); Tue, 19 Jun 2007 19:24:50 -0400 Subject: Re: Fix signalfd interaction with thread-private signals From: Benjamin Herrenschmidt To: Oleg Nesterov Cc: Linus Torvalds , Davide Libenzi , Nicholas Miell , Linux Kernel Mailing List In-Reply-To: <20070619140646.GB27343@tv-sign.ru> References: <1182064500.2798.6.camel@entropy> <1182108399.3794.4.camel@entropy> <1182125303.3794.8.camel@entropy> <1182127391.26853.207.camel@localhost.localdomain> <20070619091452.GA94@tv-sign.ru> <1182254988.26853.334.camel@localhost.localdomain> <20070619140646.GB27343@tv-sign.ru> Content-Type: text/plain Date: Wed, 20 Jun 2007 09:24:33 +1000 Message-Id: <1182295473.26853.386.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1338 Lines: 31 On Tue, 2007-06-19 at 18:06 +0400, Oleg Nesterov wrote: > On 06/19, Benjamin Herrenschmidt wrote: > > > > On Tue, 2007-06-19 at 13:14 +0400, Oleg Nesterov wrote: > > > > > The commited "Fix signalfd interaction with thread-private signals" > > > (commit caec4e8dc85e0644ec24aeb36285e1ba02da58cc) doesn't implement > > > this. > > > > Indeed, if you want what Davide described, you need to also change > > signalfd side. The patch I did merely prevents another thread from > > dequeuing somebody else private signals. > > Yes I see, but why do we need this change? Yes, we can dequeue SIGSEGV > from another thread. Just don't do it if you have a handler for SIGSEGV? Well, for such synchronous signals, it's a fairly stupid idea, especially since you can't predict who will get it. Signals such as SEGV are forced-in, which means they are force-unblocked. Thus, you can't know for sure whome of signalfd or the target thread will get it first, depending on who catches the siglock first I suppose. In one case, you'll manage to steal it, in the other, you'll thread will be killed. Ben. - 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/