Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262046AbVCTJZr (ORCPT ); Sun, 20 Mar 2005 04:25:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262055AbVCTJZr (ORCPT ); Sun, 20 Mar 2005 04:25:47 -0500 Received: from 213-239-205-147.clients.your-server.de ([213.239.205.147]:11183 "EHLO mail.tglx.de") by vger.kernel.org with ESMTP id S262046AbVCTJZl (ORCPT ); Sun, 20 Mar 2005 04:25:41 -0500 Subject: Re: Real-Time Preemption and RCU From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Manfred Spraul Cc: Ingo Molnar , "Paul E. McKenney" , dipankar@in.ibm.com, shemminger@osdl.org, Andrew Morton , Linus Torvalds , rusty@au1.ibm.com, tgall@us.ibm.com, jim.houston@comcast.net, gh@us.ibm.com, LKML In-Reply-To: <423D19FE.7020902@colorfullife.com> References: <20050318002026.GA2693@us.ibm.com> <20050318091303.GB9188@elte.hu> <20050318092816.GA12032@elte.hu> <423BB299.4010906@colorfullife.com> <20050319162601.GA28958@elte.hu> <423D19FE.7020902@colorfullife.com> Content-Type: text/plain Date: Sun, 20 Mar 2005 10:25:36 +0100 Message-Id: <1111310736.17944.24.camel@tglx.tec.linutronix.de> Mime-Version: 1.0 X-Mailer: Evolution 2.0.3 (2.0.3-2) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 899 Lines: 30 On Sun, 2005-03-20 at 07:36 +0100, Manfred Spraul wrote: > cpu 1: > acquire random networking spin_lock_bh() > > cpu 2: > read_lock(&tasklist_lock) from process context > interrupt. softirq. within softirq: try to acquire the networking lock. > * spins. > > cpu 1: > hardware interrupt > within hw interrupt: signal delivery. tries to acquire tasklist_lock. > > --> deadlock. Signal delivery from hw interrupt context (interrupt is flagged SA_NODELAY) is not possible in RT preemption mode. The local_irq_save_nort() check in __cache_alloc will catch you. When it happens from a threaded irq handler the situation is solvable by the PI code. tglx - 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/