Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753323AbYJ0Hps (ORCPT ); Mon, 27 Oct 2008 03:45:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751800AbYJ0Hpk (ORCPT ); Mon, 27 Oct 2008 03:45:40 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:33387 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751718AbYJ0Hpk (ORCPT ); Mon, 27 Oct 2008 03:45:40 -0400 Date: Mon, 27 Oct 2008 01:45:23 -0600 From: Matthew Wilcox To: "Zhao, Yu" Cc: Yu Zhao , Jesse Barnes , "linux-pci@vger.kernel.org" , "greg@kroah.com" , "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "stable@kernel.org" , Rakib Mullick Subject: Re: [PATCH] pci: Fixing drivers/pci/search.c compilation warning. Message-ID: <20081027074523.GA26094@parisc-linux.org> References: <20080928163211.GR27204@parisc-linux.org> <20081021011308.GA3889@parisc-linux.org> <490467CD.3000402@uniscape.net> <20081026183412.GX26094@parisc-linux.org> <49053313.9080706@intel.com> <20081027070745.GY26094@parisc-linux.org> <49056A2F.6030206@intel.com> <20081027072137.GZ26094@parisc-linux.org> <49056EF6.3000904@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49056EF6.3000904@intel.com> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1455 Lines: 30 On Mon, Oct 27, 2008 at 03:34:14PM +0800, Zhao, Yu wrote: > >Erm, no, the 'dev' cannot be destroyed because the caller has a refcount > >on it. The physical device backing it might have gone away. The dev > > Why does the caller have a reference count? I don't see we increase the > reference count after the 'dev' is returned by following in > pci_get_dev_by_id(): > > dev = bus_find_device(&pci_bus_type, dev_start, (void *)id, > match_pci_dev_by_id); > > And this 'dev' becomes the 'from' in the next loop, but it may be > destroyed before the 'pci_dev_get(from)', isn't it? Either you've gone back to talking about pci_find_device() [which, yes, is vulnerable to race conditions, we know that, it's not interesting to talk about it], or you're refusing to take it on faith that pci_get_dev_by_id() returns a device with an increased refcount. And if you don't believe that is true, please follow the code in bus_find_device() to prove it. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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/