Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755468Ab3JIAqJ (ORCPT ); Tue, 8 Oct 2013 20:46:09 -0400 Received: from mga02.intel.com ([134.134.136.20]:17979 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752747Ab3JIAqG (ORCPT ); Tue, 8 Oct 2013 20:46:06 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,1059,1371106800"; d="scan'208";a="407977300" Date: Wed, 9 Oct 2013 08:46:02 +0800 From: Fengguang Wu To: Greg Kroah-Hartman Cc: Russell King - ARM Linux , Linus Torvalds , xen-devel@lists.xenproject.org, Linux Kernel Mailing List Subject: Re: [xen] double fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC Message-ID: <20131009004602.GB2315@localhost> References: <20131007083505.GA22585@localhost> <20131008020918.GA1220@localhost> <20131008021452.GA6456@localhost> <20131008031152.GA8218@localhost> <20131008121742.GA29280@localhost> <20131008221417.GF25034@n2100.arm.linux.org.uk> <20131008224840.GA15303@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131008224840.GA15303@kroah.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2274 Lines: 53 On Tue, Oct 08, 2013 at 03:48:40PM -0700, Greg KH wrote: > On Tue, Oct 08, 2013 at 11:14:17PM +0100, Russell King - ARM Linux wrote: > > On Tue, Oct 08, 2013 at 08:17:42PM +0800, Fengguang Wu wrote: > > > I find the above debug messages very helpful in locating the buggy > > > driver. How about enabling it whenever CONFIG_DEBUG_KOBJECT_RELEASE is > > > enabled? Something like > > > > > > #ifdef CONFIG_DEBUG_KOBJECT_RELEASE > > > - pr_debug("kobject: '%s' (%p): %s, parent %p (delayed)\n", > > > + printk(KERN_INFO "kobject: '%s' (%p): %s, parent %p (delayed)\n", > > > kobject_name(kobj), kobj, __func__, kobj->parent); > > > > > > pr_debug() won't be displayed by default, and it depends on > > > CONFIG_DYNAMIC_DEBUG. > > > > Please consider using pr_info() instead of printk(KERN_INFO - it's > > slightly less typing. Good suggestion! > > I can see that being a useful change while we have these problematical > > instances to track down, but I do wonder whether it'll make the thing > > too noisy. Does anyone have other opinions on this point? Linus? > > Greg? > > It's going to make things really noisy at boot time, but then it should > settle down and not be bad at all. FYI, in the randconfig kernel involved in this thread, it will emit about 20 lines of dmesg. > Let's try it and see if it helps or not. OK, I'll submit a patch. These messages would allow me to do a statistic analyze of similar bugs: since I'm testing 100+ new randconfigs every day, some of them will include the buggy drivers and some not, we can collect all these lines [ 2.929669] kobject: 'drm' (ffff880006db2848): kobject_release, parent ffff880000189648 (delayed) ... [ 3.750200] kobject: 'mc13783-adc' (ffff880007707000): kobject_release, parent ffff880000189248 (delayed) , count how many times each one shows up in the GOOD kernel boots and how many show up in the BAD boots. Then we may be able to learn which drivers are likely buggy and should be manually checked. Thanks, Fengguang -- 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/