From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268260AbUIGRFD (ORCPT ); Tue, 7 Sep 2004 13:05:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268130AbUIGRCV (ORCPT ); Tue, 7 Sep 2004 13:02:21 -0400 Received: from waste.org ([209.173.204.2]:10173 "EHLO waste.org") by vger.kernel.org with ESMTP id S268175AbUIGQ7t (ORCPT ); Tue, 7 Sep 2004 12:59:49 -0400 Date: Tue, 7 Sep 2004 11:59:42 -0500 From: Matt Mackall To: Jeff Moyer Cc: linux-kernel@vger.kernel.org Subject: Re: netpoll trapped question Message-ID: <20040907165942.GY31237@waste.org> References: <16692.45331.968648.262910@segfault.boston.redhat.com> <20040906213502.GU31237@waste.org> <16701.58093.63886.734877@segfault.boston.redhat.com> <20040907165014.GX31237@waste.org> <16701.59261.688607.284454@segfault.boston.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16701.59261.688607.284454@segfault.boston.redhat.com> User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 07, 2004 at 12:53:17PM -0400, Jeff Moyer wrote: > mpm> A random lock private to a given driver, for instance one taken on > mpm> entry to the IRQ handler. If said driver tries to do a printk inside > mpm> that lock and we recursively call the handler in netconsole, we're in > mpm> trouble. These are the issues that will have to be cleaned up in > mpm> individual drivers. So far, I haven't seen any reports, but I'm pretty > mpm> sure such cases exist. I suppose it's also possible for us to disable > mpm> recursion in netconsole instead of at the netpoll level. > > Recursion in netconsole is protected by the console semaphore. Yes, true. But we're still in trouble if we have nic irq handler -> take private lock -> printk -> netconsole -> nic irq handler -> take private lock. See? -- Mathematics is the supreme nostalgia of our time.