On 2/11/23 16:51, Linus Torvalds wrote:
On Sat, Feb 11, 2023 at 1:41 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:@@ -2941,7 +2944,10 @@ void device_initialize(struct device *de kobject_init(&dev->kobj, &device_ktype); INIT_LIST_HEAD(&dev->dma_pools); mutex_init(&dev->mutex); - lockdep_set_novalidate_class(&dev->mutex); + if (!lockdep_static_obj(dev)) { + lockdep_register_key(&dev->mutex_key); + lockdep_set_class(&dev->mutex, &dev->mutex_key); + } spin_lock_init(&dev->devres_lock); INIT_LIST_HEAD(&dev->devres_head); device_pm_init(dev);So I think this is the right thing to do, but I note that while that lockdep_set_novalidate_class() was "documented" to only be for 'dev->mutex' by scripts/checkpatch.pl, that horrific thing is also used by md/bcache/btree.c for the mca_bucket_alloc(). Can we *please* get rid of it there too (it was added by the initial code, and never had any explicit excuse for it), possibly by using the same model. And then we could get rid of lockdep_set_novalidate_class() entirely. That would be a good thing.
Yeah, what bcache really needs (and presumably dev->mutex as well) is just to disable lockdep checking for self-deadlock of that lock type, since it's got its own deadlock avoidance and the subclass thing isn't good enough.
I've got a patch that should do what we want, replying from my other account with it.
