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    SubjectRe: [PATCH 3/4] modules: proper cleanup of kobject without CONFIG_SYSFS
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    On Friday 23 May 2008 03:54:15 Greg KH wrote:
    > On Thu, May 22, 2008 at 07:20:22PM +1000, Rusty Russell wrote:
    > > On Tuesday 20 May 2008 19:59:48 Denis V. Lunev wrote:
    > > > kobject: '<NULL>' (ffffffffa0104050): is not initialized, yet
    > > > kobject_put()
    > >
    > > Thanks Denis.
    > >
    > > This patch masks a deeper problem; looks like you can't load any modules
    > > with CONFIG_SYSFS=n:
    > >
    > > kernel/module.c:
    > > int mod_sysfs_init(struct module *mod)
    > > {
    > > int err;
    > > struct kobject *kobj;
    > >
    > > if (!module_sysfs_initialized) {
    > > printk(KERN_ERR "%s: module sysfs not initialized\n",
    > > mod->name);
    > > err = -EINVAL;
    > > goto out;
    > > }
    > >
    > > AFAICT, module_sysfs_initialized is not ever set if !CONFIG_SYSFS.
    > >
    > > I can't see the point of module_sysfs_initialized. It was introduced by
    > > Greg in commit 823bccfc ("remove "struct subsystem" as it is no longer
    > > needed").
    > >
    > > Greg, what were you trying to do here? Modules can't be loaded before
    > > param_sysfs_init(): are you trying to handle the case where the
    > > kset_create_and_add() fails?
    >
    > Yes. Previously you were never detecting that if the subsystem was not
    > properly created (for whatever reason), we could fail horribly when
    > trying to load a module.

    Well, my policy is to crash when allocations fail during boot, rather than
    traversing untested code paths. But since that code already exists, I'm not
    religious enough to argue about it; just wanted to see if there was some
    subtlety I was missing.

    > Now we at least detect that problem, is is causing an issue somehow? I
    > think you have now seen that we can load modules with CONFIG_SYSFS=n,
    > otherwise people would have complained by now (not that anyone actually
    > runs that kind of configuration that I know of...)

    Yes, thanks. But it seems noone has removed a module in such a config since
    April 2007.

    The module/sysfs code is messy though: we do most sysfs stuff only under
    CONFIG_SYSFS, which seems overkill since at a glance it should just neatly do
    nothing. Do you have the cycles and inclination to take a look at it?

    Thanks,
    Rusty.


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