Messages in this thread | | | Date | Mon, 9 Jun 2008 19:15:21 +0200 | From | Cornelia Huck <> | Subject | Re: [bug, 2.6.26-rc4/rc5] sporadic bootup crashes in blk_lookup_devt()/prepare_namespace() |
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On Mon, 9 Jun 2008 09:15:40 -0700 (PDT), Linus Torvalds <torvalds@linux-foundation.org> wrote:
> And this is all still ignoring the locking issue, of course. It would be > trivial to just remove the block_class_lock, and change > > mutex_[un]lock(&block_class_lock); > > into > > down|up(&block_class.sem); > > except for _one_ case, which is > > bdev_map = kobj_map_init(base_probe, &block_class_lock); > > which really wants a mutex, not a sempahore. > > So to fix that, we'd need to make the class->sem be a mutex, and pass that > in. Which is probably a good change too, but makes the whole thing much > bigger.
The driver core changes in -next convert class->sem to class->p->class_mutex, which makes it non-accessible to drivers. Most of the locking is easily done through converting to the class iterator functions, but there are some cases where this is not going to work:
- The {register,unregister}_blkdev() functions, which don't directly involve the class. - The iterators for /proc/partitions, which take the lock in part_start() and give it up again in part_stop().
Maybe we need a possibilty for a driver to lock a class from outside?
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