Re: panic: ifc_free_unit: bit is already cleared

Brooks Davis wrote:
> On Wed, Oct 12, 2005 at 10:06:02AM +1300, Andrew Thompson wrote:
> 
>>On Mon, Oct 10, 2005 at 01:29:00PM -0700, Brooks Davis wrote:
>>
>>>On Mon, Oct 10, 2005 at 03:22:08PM +1300, Andrew Thompson wrote:
>>>
>>>>On Mon, Oct 10, 2005 at 03:28:49AM +0400, Yar Tikhiy wrote:
>>>>
>>>>>FWIW, I tried to look at the $subject problem since I had had it
>>>>>before, but just got a different panic:
>>>>>
>>>>>        Memory modified after free 0xc140b000(4092) val=deadc0dc _at_ 0xc140b000
>>>>>        panic: Most recently used by clone
>>>>>
>>>>>The clone code seems to have decremented something (refcount?) twice
>>>>>after freeing the memory chunk.
>>>>
>>>>I have been testing this patch and I think it fixes all the problems
>>>>discussed.
>>>>
>>>>It changes refcounting to count the number of cloned interfaces so
>>>>ifc_units is only freed when its safe. A new function has been added to
>>>>decrement this when a simple cloner module is unloaded. The cloner is
>>>>still detached first to prevent the race.
>>>>
>>>>In most cases the change is as simple as:
>>>
>>>I don't see any reason why you can't just replace the specific destroy
>>>calls with calls to ifc_simple_destroy().  That would avoid expanding
>>>the API.
>>
>>I have updated the patch and yes, its a nicer way to do it. Please
>>review.
>>
>>Ive run through interations of create/kldunload with bridge, disc,
>>faith, gif, gre and ppp with extra printf's and its freeing correctly.
> 
> 
> This looks good to me, thanks for working on this and doing the
> <ifn>_destory removals.  Let's see about getting this committed.
> 
> Slightly longer term I think should consider hanging the interface list
> off the cloner or maybe off some more generic per driver struct so
> if_clone_detach() can destroy the interfaces and the unload code becomes
> a one-liner in most cases.  The current code is a result of not wanting
> to mess with the drivers too much initially, but I think we need to
> start looking at moving more bits into the support code.  After all, if
> we only write something once instead of once per interface, that's a lot
> less opportunities to screw up. :)

There's also the changes I have to pass parameter blocks on clone create...

	Sam