Messages in this thread | | | Date | Thu, 29 Nov 2007 11:12:51 +0100 | From | Cornelia Huck <> | Subject | Re: [RFC] New kobject/kset/ktype documentation and example code |
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On Wed, 28 Nov 2007 14:18:18 -0500 (EST), Alan Stern <stern@rowland.harvard.edu> wrote:
> On Wed, 28 Nov 2007, Cornelia Huck wrote: > > > We should perhaps add a bit fat warning here: > > > > Note that once you registered your kobject via kobject_add(), you must > > never use kfree() to free it directly. The only safe way is to use > > Slightly ambiguous. Instead just say: > > If you have initialized your kobject via kobject_init() or > kobject_register(), you must not deallocate the kobject anywhere other > than its release() method (which is invoked during the final > kobject_put() call). Otherwise the kernel will leak memory.
And references to the kobject's kset...
> > > > One important point cannot be overstated: every kobject must have a > > > release() method, and the kobject must persist (in a consistent state) > > > until that method is called. > > > > Which is especially hurting if you use kobjects in modules. (Which > > reminds me: Must dig up the patchset that fixes the module unload vs. > > release problem.) > > In theory modules shouldn't present a problem -- especially if Greg > merges the "Kobjects: drop child->parent ref at unregistration" patch. > > When a module is unloaded, it has to unregister all its kobjects, which > should force all their children to be unregistered too. At that time > the children's drivers should drop all their references to the parent > kobject, leaving only references held by the module being unloaded. > Presumably it can arrange to drop its own references before its exit() > routine returns. > > The only problem arises when a child's driver retains a reference to > the parent kobject. If things are done properly, this reference should > involve incrementing the module count -- which would prevent the module > from being unloaded in the first place.
This still leaves the possibility that random code may grab a reference once the kobject is present in the tree and lookupable. You gave up the control of the number of references to your object once you made it public. - 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/
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