Re: device_del() and references

Russell King
2006-11-14T11:24:16Z

On Tue, Nov 14, 2006 at 08:40:00AM +0100, Pierre Ossman wrote:
> When a card driver has obtained a reference to a card, what makes sure
> we do not destroy that card from under its feet?

Essentially, the driver model. (see the answer to your paragraph below.)

> I suspect that device_del() doesn't return until remove() has been
> called and that our requirement is that the card driver must have
> released all references to the card before its remove routine exits.

Your sentence is confusing - which "remove()" are you talking about
here? If you're talking about mmc_blk_remove() then that's correct.

> If so, then there is the risk of a race in mmc_block. What guarantees
> that the request handler isn't running in parallel with the remove
> function? Again, I suspect that del_gendisk() might grab the queue lock,
> but as there might be stuff left in the queue, this seems insufficient.

Hmm, not sure here. I think you might be right, but the block layer is
*extremely* finaky when it comes to removing stuff.

In short, I don't know - I've forgotten quite a bit about the low level
block interface with MMC since it's something I did once and only once.

Maybe Jens has some ideas?

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core