From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFD driver-core] Lifetime problems of the current driver model Date: Sat, 31 Mar 2007 12:15:02 +0900 Message-ID: <460DD236.4030804@gmail.com> References: <460CDBA6.5030608@gmail.com> <20070330151926.18fc12a0@gondolin.boeblingen.de.ibm.com> <460D0E78.3040200@gmail.com> <20070330154042.4c7deb72@gondolin.boeblingen.de.ibm.com> <460D178F.4000500@gmail.com> <20070330165251.7beffc7c@gondolin.boeblingen.de.ibm.com> <460D27E3.2050602@gmail.com> <20070330213101.7aa7babf@gondolin.boeblingen.de.ibm.com> <460DD1B0.4080605@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from wr-out-0506.google.com ([64.233.184.228]:23384 "EHLO wr-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964785AbXCaDPO (ORCPT ); Fri, 30 Mar 2007 23:15:14 -0400 Received: by wr-out-0506.google.com with SMTP id 76so905033wra for ; Fri, 30 Mar 2007 20:15:13 -0700 (PDT) In-Reply-To: <460DD1B0.4080605@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Cornelia Huck Cc: gregkh@suse.de, hugh@veritas.com, dmitry.torokhov@gmail.com, oneukum@suse.de, maneesh@in.ibm.com, rpurdie@rpsys.net, James.Bottomley@SteelEye.com, Jeff Garzik , lkml , "linux-ide@vger.kernel.org" , SCSI Mailing List Tejun Heo wrote: > Cornelia Huck wrote: >> On Sat, 31 Mar 2007 00:08:19 +0900, >> Tejun Heo wrote: >> >>> (3) make sure all existing kobjects are released by module exit function. >>> >>> For example, let's say there is a hypothetical disk device /dev/dk0 >>> driven by a hypothetical driver mydrv. /dev/dk0 is represented like the >>> following in the sysfs tree. >>> >>> /sys/devices/pci0000:00/0000:00:1f.0/dk0/{myknob0,myknob1} >>> >>> Owner of both attrs myknob0 and myknob1 is mydrv and opening either >>> increases the reference counts of dk0 and mydrv and closing does the >>> opposite. >>> >>> * When there is no opener of either knob and the /dev/dk0 isn't used by >>> anyone. Reference count of dk0 is 1, mydrv 0. >> Hm, but as long as dk0 is registered, it can be looked up and someone >> could get a reference on it. > > Yeah, exactly. That's why any getting any kobject reference backed by a > module must be accompanied by try_module_get(). > > int mydrv_get_dk(struct dk *dk) > { > rc = try_module_get(mydrv); > if (rc) > return rc; > kobject_get(&dk->kobj); > return 0; > } And one more thing just in case. In the above code, try_module_get() and kobject_get() must be and is atomic w.r.t. try_stop_module(). That's why we do the following. stop_machine_run(__try_stop_module, &sref, NR_CPUS);. -- tejun