From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Mackall Subject: Re: [PATCH] Prevent netpoll hanging when link is down Date: Mon, 11 Oct 2004 11:58:52 -0500 Sender: netdev-bounce@oss.sgi.com Message-ID: <20041011165851.GN31237@waste.org> References: <20041007214505.GB31558@wotan.suse.de> <20041008090610.70d7e183@pirandello> <20041008220001.GE31237@waste.org> <20041008151839.01823e0c.akpm@osdl.org> <20041010205928.6e54df7e.davem@davemloft.net> <20041011154000.GB26350@wotan.suse.de> <20041011162224.GL31237@waste.org> <20041011163226.GG26350@wotan.suse.de> <20041011163601.GM31237@waste.org> <20041011164315.GH26350@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , Andrew Morton , colin@colino.net, netdev@oss.sgi.com Return-path: To: Andi Kleen Content-Disposition: inline In-Reply-To: <20041011164315.GH26350@wotan.suse.de> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Mon, Oct 11, 2004 at 06:43:15PM +0200, Andi Kleen wrote: > > It's not recursion on printk that's a problem, it's recursion on > > ->poll() and attempting to take whatever internal driver locks. > > There is no recursion on poll because printk will never call into > the low level console driver when the console sem is already taken. Ergh, you deleted the context. Again, imagine we're originally in ->poll() for _a non-netpoll-related reason_. In other words, the console sem is not taken, because we're just doing routine network I/O. While in poll(), we take a private driver lock. Then for whatever reason, we printk -> netconsole -> netpoll -> poll() again where we attempt to retake the private driver lock. > P.S.: I made the same mistake long ago, but akpm set me straight. I'm pretty sure this case is different. -- Mathematics is the supreme nostalgia of our time.