From: Joel Becker Date: Mon, 16 Jun 2008 11:06:43 -0700 Subject: [Ocfs2-devel] [RFC] configfs: module reference counting rules In-Reply-To: <20080616123912.GR30804@localhost> References: <20080612235410.GC4012@localdomain> <20080613033309.GE20581@mail.oracle.com> <20080613095159.GH30804@localhost> <20080613202605.GD20576@mail.oracle.com> <20080613222744.GB4153@localdomain> <20080614084701.GA9657@mail.oracle.com> <20080616123912.GR30804@localhost> Message-ID: <20080616180643.GC9657@mail.oracle.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Louis Rilling Cc: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org On Mon, Jun 16, 2008 at 02:39:12PM +0200, Louis Rilling wrote: > On Sat, Jun 14, 2008 at 01:47:01AM -0700, Joel Becker wrote: > IMHO, what really hurts configfs is that the unregister_subsystem() vs > mkdir() race is not solved unless mkdir() tries to grab a reference on the > subsystem's module. And the current code of mkdir() does not ensure that in the > "several modules" case. Valid point. It really does assume that the owner is always the same. Have to think about whether that's a big deal. > I do something like this (and this works): I believe it works. It looks fine. I'd personally do it more like what I displayed, wrapping release() rather than creating a separate operations abstraction and overriding item_operations, but as you point out that's just implementation. > > Why can't mod_b provide a ->release() that does > > module_put(self)? > > Because this is simply wrong. Doing module_put(self) exposes the modules's > function to be run while another cpu unloads the module. Note how I solve this How so? As long as the module_put() is the last thing, you're fine. That said, we both have better solutions with our wrappered functions. Joel -- "If you took all of the grains of sand in the world, and lined them up end to end in a row, you'd be working for the government!" - Mr. Interesting Joel Becker Principal Software Developer Oracle E-mail: joel.becker at oracle.com Phone: (650) 506-8127