Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757706AbYABFiF (ORCPT ); Wed, 2 Jan 2008 00:38:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754606AbYABFhy (ORCPT ); Wed, 2 Jan 2008 00:37:54 -0500 Received: from hs-out-0708.google.com ([64.233.178.251]:49413 "EHLO hs-out-2122.google.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752547AbYABFhx (ORCPT ); Wed, 2 Jan 2008 00:37:53 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=vjEHj/y9l9tyTbQguHRxQN7fEcqqgBpnh/T0sDYlWIoia8VWU52cLARhi8clPOJocn55eJNyyoRdJPXxHC3OO2fGXGBQC9KLF/MlmQkPvOMhAEwbxjVzLX4fFIcOAoGDeVSS0tkmIsU2Rq64hQBteXrtfrjVIN+7MdWQNHj9S8I= Message-ID: Date: Wed, 2 Jan 2008 13:37:52 +0800 From: "Dave Young" To: "Greg KH" Subject: Re: [PATCH 01/12] Use mutex instead of semaphore in driver core Cc: "Greg KH" , "Peter Zijlstra" , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org In-Reply-To: <20080102051828.GA24431@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <1198892544.6821.103.camel@twins> <1198893445.6821.108.camel@twins> <20071229044200.GA16712@suse.de> <20071229170730.GA1351@kroah.com> <20080102051828.GA24431@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2531 Lines: 61 On Jan 2, 2008 1:18 PM, Greg KH wrote: > On Wed, Jan 02, 2008 at 08:54:53AM +0800, Dave Young wrote: > > On Dec 30, 2007 1:07 AM, Greg KH wrote: > > > > > > On Sat, Dec 29, 2007 at 03:07:30PM +0800, Dave Young wrote: > > > > On Dec 29, 2007 1:06 PM, Dave Young wrote: > > > > > > > > > > On Dec 29, 2007 12:42 PM, Greg KH wrote: > > > > > > On Sat, Dec 29, 2007 at 10:36:49AM +0800, Dave Young wrote: > > > > > > > > > > > > > > > The full boot dmesg with lockdep output is out, there's one warnings in it : > > > > > > > > > > > > Please fix that warning before the next repost of these patches (along > > > > > > with fixing the problem of them not being able to be applied and > > > > > > successfully built at every point in the series...) > > > > > > > > > > > > > > > > Ok, thanks, I will fix them and repost. > > > > > > > > > > > > > Hi, > > > > After digging the code, I feel hard to fix the lockdep warning due to > > > > some misterious relationship with usb. > > > > > > > > Could someone help on this? thanks. > > > > > > My question back to you is why are you doing this conversion? Have you > > > found that it is needed for something? Are there problems in the -rt > > > kernels that this conversion helps with? Or is it just a janitorial > > > "convert semaphore to mutex" type thing. > > > > Sorry for delay-reply because recently I have little free time. > > > > Mutex is lightweighter than semaphore, the device/class is used > > heavily in kernel, so I think the convert would be worth. > > But is the usage of this semaphore in the class code really a problem? > Has it been seen to cause issues anywhere? Does it show up on any > benchmarks as being something that really needs to be replaced? > > All of the places this is used should be on a "slow" code-path, and the > semaphores themselves should very rarely ever have to block anyone under > normal usages. > > Without any real problems being reported for this, I wouldn't worry > about this, the effort involved is non-trivial as you are quickly > finding out :) > Maybe not a big problem, but AFAIK convertion is better. For Benchmarks, not yet. OTOH, as you said the effort to do this is indeed a problem. Regards dave -- 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/