Re: [Patch -mm 0/3] RFC: module unloading vs. release function

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 4/16/07, Greg KH <[email protected]> wrote:
On Mon, Apr 16, 2007 at 03:03:16PM -0400, Dmitry Torokhov wrote:
> On 4/16/07, Greg KH <[email protected]> wrote:
> >On Mon, Apr 16, 2007 at 02:30:17PM -0400, Dmitry Torokhov wrote:
> >> On 4/16/07, Cornelia Huck <[email protected]> wrote:
> >> >Hi,
> >> >
> >> >based on the discussion in "How should an exit routine wait for
> >> >release() callbacks?", I've cooked up some patches that make module
> >> >unload wait until the last reference for a kobject has been dropped.
> >> >This should plug the "release function in already deleted module" race;
> >> >however, if the last kobject_put() from the module containing the
> >> >release function is not in the module's exit function, there's still a
> >> >small window (not sure if and how to plug this).
> >>
> >> Unfortunately all this "wait for refcount in module's exit" schemas
> >> lead to the following deadlock:
> >>
> >>        rmmod my_module < /path/to/some/file/incrementing/my/refcount
> >
> >No, it should just return "module in use" as the reference count it
> >grabbed before rmmod is called.
> >
>
> No, because it it were module's refcount we woudl not have problem
> with ->release() to begin with. It is object's refcount.

Yes, but with these patches, we are incrementing that reference count
when the kobject is created, which will cause this to fail.


Then you will never be able to unload the module, not with the current
module tools.

> >But either way, that's just foolish to try to prevent that from failing
> >:)
>
> Why? It works now for most of teh subsystems.

That's because it is buggy :)


Depends on the subsystem.

--
Dmitry
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux