Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758016AbYARB4G (ORCPT ); Thu, 17 Jan 2008 20:56:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756846AbYARBzk (ORCPT ); Thu, 17 Jan 2008 20:55:40 -0500 Received: from wa-out-1112.google.com ([209.85.146.177]:35016 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751681AbYARBzj (ORCPT ); Thu, 17 Jan 2008 20:55:39 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=YjK0+M+ejBXMrXWh7Bp/jTelAwHlOZftfRgdh4jmL9fXL3NW0AhTZRBjrolXNWPM3CSWhO2Y4GJyiLopU7e99p4i6PeHhmAz6a3YRyJyWhf8q0FHCp24OZG3XDlenrwhUxbewdxP1wUey9c+doaKbCeqIP/AqNo/8RFuMgwytwY= Message-ID: <3ae72650801171755k85c4245i3b4c46a84ae8f52d@mail.gmail.com> Date: Fri, 18 Jan 2008 02:55:38 +0100 From: "Kay Sievers" To: "Dave Young" Subject: Re: [PATCH 7/7] driver-core : convert semaphore to mutex in struct class Cc: "Jarek Poplawski" , "Alan Stern" , "Greg KH" , stefanr@s5r6.in-berlin.de, "David Brownell" , "Kernel development list" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080117194728.GA2598@ami.dom.local> <20080117203155.GA2791@ami.dom.local> <20080117232626.GC2905@ami.dom.local> X-Google-Sender-Auth: 2c8e8abd037dd2b0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3632 Lines: 76 On Jan 18, 2008 2:42 AM, Dave Young wrote: > > On Jan 18, 2008 7:26 AM, Jarek Poplawski wrote: > > > > On Thu, Jan 17, 2008 at 09:31:55PM +0100, Jarek Poplawski wrote: > > > On Thu, Jan 17, 2008 at 02:57:36PM -0500, Alan Stern wrote: > > > > On Thu, 17 Jan 2008, Jarek Poplawski wrote: > > > > > > > > > On Thu, Jan 17, 2008 at 10:16:30AM -0500, Alan Stern wrote: > > > > > > On Thu, 17 Jan 2008, Dave Young wrote: > > > > > > > > > > > > > > Your meaning isn't clear. Do you mean that your patch doesn't generate > > > > > > > > any lockdep warnings at all? Or do you mean that it generates a single > > > > > > > > lockdep warning at boot time and then no more warnings afterward? > > > > > > > > > > > > > > I means the latter one. > > > > > > > > > > > > That's very bad. > > > > > > > > > > > > For each type of violation, lockdep only gives one error message. So > > > > > > the fact that you get one message at boot time and then no more doesn't > > > > > > mean the code is almost right -- it probably means the code has lots of > > > > > > errors and you're seeing only the first one. > > > > > > > > > > I hope it's better than this: lockdep really stops checking after first > > > > > warning, but I've understood from David's description that after fixing > > > > > this one place lockdep seems to be pleased. > > > > > > > > That isn't what Dave said above; he said that lockdep produces a single > > > > warning at bootup. If he did mention anything about one place being > > > > fixed up or lockdep being pleased, it was a while back and I've lost > > > > track of it. > > > > > > > > If I recall correctly the nature of the warning was that a method > > > > routine for one class (called with the class's mutex held) was creating > > > > a second class and locking that class's mutex. In principle this is > > > > perfectly legal and should be allowed for arbitrary depths of nesting, > > > > even though it is the sort of thing lockdep is currently unable to > > > > handle. > > > > > > You are definitely right! After first reading Dave's description I got > > > it the same way, but after re-reading I probably was misled with this > > > "thus"! Only now I've had a look at this warning and there is really > > > mutex_lock_nested(). Sorry Alan! > > > > But, on the other hand, mutex_lock() is really mutex_lock_nested(), and > > after second checking this lockdep warning from Jan. 3, it seems > > impossible it was get after this patch... > > > > Dave, could you please answer with full sentence if there is any lockdep > > warning possible after applying these 1-7/7 patches, and if so, attach > > current warning? Otherwise, I'll have apologized for this everybody from > > the list soon! > > After digging the class usage code again, I found that the only > possible double lock place is the class_interface_register/unregister > in which the class_device api could be called. > > The scsi and pcmcia use the class_interface api, I just found the > warning above caused by scsi part then. > > So I think I will need to use mutex_lock_nesting for the > class_device_* functions. All "struct class_device" stuff will go away very soon, and only "struct device" will stay. The conversion for remaining users is already in -mm. Only SCSI and IB are missing, but experimental patches for these exist already. Kay -- 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/