So I was perusing the code in lib/kobject.c, and I saw this:
void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
{
// [a couple of of parameter checks...]
if (kobj->state_initialized) {
/* do not error out as sometimes we can recover */
printk(KERN_ERR "kobject (%p): tried to init an
initialized "
"object, something is seriously wrong.\n", kobj);
dump_stack();
}
in other words the first thing you do is check a member of the
structure you're supposed to be initializing -- if someone just
kmalloc()s a struct kobject and passes it into this function, there's
a good chance that state_initialized won't be zero. In fact, with
slab debugging on, it's guaranteed to be poisoned with a non-zero
value.
So are users supposed to be zeroing out struct kobjects before
initializing them? If so, this should probably be documented.
And also the code in kobject_init() that sets other fields to be zero
can also be removed:
kobj->state_in_sysfs = 0;
kobj->state_add_uevent_sent = 0;
kobj->state_remove_uevent_sent = 0;
Let me know if the intention is that everyone should zero out their
kobjects when they initialize them, and I'll send a patch updating the
documentation.
There's another similar booby-trap in kobject_init_and_add(), which
ends up calling into kobject_set_name_vargs(), which does
/* Free the old name, if necessary. */
kfree(kobj->name);
which is generally a bad thing if kobj->name has not been initialized.
Thanks,
Roland
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