Messages in this thread | | | Subject | Re: [KJ][PATCH] Correct misc_register return code handling in several drivers | From | Benjamin Herrenschmidt <> | Date | Wed, 25 Oct 2006 08:42:42 +1000 |
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On Tue, 2006-10-24 at 08:53 -0400, Neil Horman wrote: > On Tue, Oct 24, 2006 at 01:34:34PM +1000, Benjamin Herrenschmidt wrote: > > On Mon, 2006-10-23 at 13:19 -0400, Neil Horman wrote: > > > Hey All- > > > Janitor patch to clean up return code handling and exit from failed > > > calls to misc_register accross several modules. > > > > The patch doesn't match the description... What are those INIT_LIST_HEAD > > things ? Is this something I've missed or is this a new requirement for > > all misc devices ? Can't it be statically initialized instead ? > > > > The INIT_LIST_HEAD is there to prevent a potential oops on module removal. > misc_register, if it fails, leaves miscdevice.list unchanged. That means its > next and prev pointers contain NULL or garbage, when both pointers should contain > &miscdevice.list. If we don't do that, then there is a chance we will oops on > module removal when we do a list_del in misc_deregister on the moudule_exit > routine. I could have done this statically, but I thought it looked cleaner to > do it with the macro in the code.
Hrm... I see, but I still for some reason don't like it that much.. I'd rather have misc_register() do the initialisation unconditionally before it can fail, don't you think ?
We would theorically have a similar problem with any driver that does
xxxx_register(&static_struct)
and
xxxx_unregister(&static_struct)
(pci, usb, etc...)
As long as there are list heads involved. I think the proper solution here is to have either the unregister be smart and test for NULL/NULL or the register initialize those fields before it has a chance to fail.
Ben.
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