From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932919Ab3HNQv4 (ORCPT ); Wed, 14 Aug 2013 12:51:56 -0400 Received: from perches-mx.perches.com ([206.117.179.246]:33630 "EHLO labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932815Ab3HNQvz (ORCPT ); Wed, 14 Aug 2013 12:51:55 -0400 Message-ID: <1376499114.1949.81.camel@joe-AO722> Subject: Re: Dynamic debug on by default? From: Joe Perches To: Sarah Sharp Cc: Xenia Ragiadakou , Jason Baron , Greg KH , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 14 Aug 2013 09:51:54 -0700 In-Reply-To: <20130814164022.GA22934@xanatos> References: <20130814164022.GA22934@xanatos> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.6.4-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2013-08-14 at 09:40 -0700, Sarah Sharp wrote: > Hi Xenia, > > I'm a bit confused. I thought that debugging messages would be turned > off by default for a module if CONFIG_DYNAMIC_DEBUG was turned on. When > I tested your patch to remove the CONFIG_USB_XHCI_HCD_DEBUGGING and just > use dev_dbg, the messages from the xHCI driver appeared in dmesg by > default. > > That generates a lot of log spew. We can have distros add a boot > parameter option to turn off debug messages, but that boot parameter is > limited to 1023 characters. I'm concerned that if more drivers add > dynamic debugging, the distros will eventually run out of space in the > dynamic debugging boot parameter. I know Greg was ripping out debugging > config options in other USB drivers, so this is a bit concerning. > > Jason, is there a way within the xHCI driver to say that dynamic > debugging should be off by default? I've looked through the > documentation, and I can't find anything like that documented. #undefine DEBUG > I've attached my .config file, in case I have something misconfigured. Because of: drivers/usb/host/Makefile:ccflags-$(CONFIG_USB_DEBUG) := -DDEBUG you probably want to turn this off CONFIG_USB_DEBUG=y when dynamic_debug is on. CONFIG_DYNAMIC_DEBUG=y This will cause all pr_debug/dev_dbg statements to be emitted without specific enabling via the dynamic_debug control file. (from include/linux/dynamic_debug.h) #if defined DEBUG #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT #else #define _DPRINTK_FLAGS_DEFAULT 0 #endif