From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dave Young" Subject: Re: [PATCH 1/3][-mm] add class_reclassify macro Date: Tue, 20 May 2008 19:05:21 +0800 Message-ID: References: <20080520095553.GA3201@darkstar.te-china.tietoenator.com> <20080520030232.fc91b64e.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from ti-out-0910.google.com ([209.85.142.185]:36730 "EHLO ti-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765597AbYETLFX (ORCPT ); Tue, 20 May 2008 07:05:23 -0400 Received: by ti-out-0910.google.com with SMTP id b6so1099984tic.23 for ; Tue, 20 May 2008 04:05:21 -0700 (PDT) In-Reply-To: <20080520030232.fc91b64e.akpm@linux-foundation.org> Content-Disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Andrew Morton Cc: greg@kroah.com, matthew@wil.cx, kay.sievers@vrfy.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org On Tue, May 20, 2008 at 6:02 PM, Andrew Morton wrote: > On Tue, 20 May 2008 17:55:54 +0800 Dave Young wrote: > >> Converting class semaphore to mutex cause lockdep warnings due to >> class_interface_register/unregister will possible call device_add/del > > Shouldn't we just fix that? Andrew, could you tell more? > >> For the class_interface users here add a class_reclassify macro to >> reclassify the lock class of their struct class. >> >> Signed-off-by: Dave Young >> >> --- >> include/linux/device.h | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> --- linux/include/linux/device.h 2008-05-19 12:29:54.000000000 +0800 >> +++ linux.new/include/linux/device.h 2008-05-19 14:42:25.000000000 +0800 >> @@ -529,4 +529,11 @@ extern const char *dev_driver_string(str >> MODULE_ALIAS("char-major-" __stringify(major) "-" __stringify(minor)) >> #define MODULE_ALIAS_CHARDEV_MAJOR(major) \ >> MODULE_ALIAS("char-major-" __stringify(major) "-*") >> + >> +#define class_reclassify(class) \ >> +do { \ >> + static struct lock_class_key class_key; \ >> + lockdep_set_class_and_name(&(class)->mutex, &class_key, \ >> + (class)->name); \ >> +} while (0) >> #endif /* _DEVICE_H_ */ > > I think it would need a lavish comment explaining what it is for, and > the reasons for its existence. Yes, will do. > > Perhaps this should be a kernel-wide thing in lockdep.h. But then that > would invite people to use it, and it looks like a bad thing. I agree. There's wellmeant lockdep warnings for some safe code logic every some time. Yes, this macro violates the lockdep class-based rules, but it can act as just supplementary. And it could help some users. > > device.h does not include lockdep.h, so putting this here assumes that > callees have already included lockdep.h. This is the sort of > assumption which leads to compilation errors. > My wrong, thanks. Regards dave