Messages in this thread | | | Date | Wed, 10 Sep 2003 23:26:49 -0700 | From | Greg KH <> | Subject | Re: [RFC] add kobject to struct module |
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On Thu, Sep 11, 2003 at 11:13:25AM +1000, Rusty Russell wrote: > > > > But in looking at your patch, I don't see why you want to separate the > > > > module from the kobject? What benefit does it have? > > > > > > The lifetimes are separate, each controlled by their own reference > > > count. I *know* this will work even if someone holds a reference to > > > the kobject (for some reason in the future) even as the module is > > > removed. > > > > Correct me if I'm wrong, but this sounds similar to the networking > > refcount problem. The reference on the containing object is the > > interesting one, as far as visibility goes. As long as its positive, the > > module is active. > > There are basically two choices: ensure that the reference count is > taken using try_module_get() (kobject doesn't have an owner field, so > it does not match this one), or ensure that an object isn't ever > referenced after the module cleanup function is called. > > In this context, that means that the module cleanup must pause until > the reference count of the kobject hits zero, so it can be freed. > > Implementation below.
Ah, nice catch on that bug. I like this implementation.
On a site note, can't you just use a "struct completion" to use for your waiting? Or do you need to do something special here?
> BTW, The *real* answer IMHO is (this is 2.7 stuff:) > > 1) Adopt a faster, smaller implementation of alloc_percpu (this patch > exists, needs some arch-dependent love for ia64). > 2) Use it to generalize the current module reference count scheme to > a "bigref_t" (I have a couple of these) > 3) Use that in kobjects.
Hm, I don't know if kobjects really need to get that heavy.
> 4) Decide that module removal is not as important as it was, and not > all modules need be removable (at least in finite time). > 5) Use the kobject reference count everywhere, including modules. > > This would make everything faster, except for the case where someone > is actually waiting for a refcount to hit zero: for long-lived objects > like kobjects, this seems the right tradeoff.
As more people use kobjects, I think we'll see some pretty short lifespans...
But yes, that's all 2.7 dreams :)
thanks,
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