Messages in this thread Patch in this message | | | Date | Mon, 8 Feb 2010 10:38:52 -0500 (EST) | From | Alan Stern <> | Subject | Re: [Patch 0/2] sysfs: fix s_active lockdep warning |
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On Fri, 5 Feb 2010, Peter Zijlstra wrote:
> > But for now perhaps a compromise is in > > order. We could make the switch from semaphores to mutexes while > > avoiding lockdep issues by assigning the device mutexes to a > > "don't-verify" class. Is there such a thing, or could it be added? > > Something like the below might work, but it should go along with a > checkpatch.pl mod to ensure we don't grow any new users (just don't feel > like brushing up my perl fu enough to actually make sense of that > script)
I tried this out and it does work; no more lockdep warnings during bootup. The complete patch is below.
But before we apply this, it might be worthwhile to spend a little time figuring out how many independent device trees there really are and whether they can be handled with separate depth-associated lockdep classes. It's not at all obvious that they can.
Alan Stern
Index: usb-2.6/include/linux/lockdep.h =================================================================== --- usb-2.6.orig/include/linux/lockdep.h +++ usb-2.6/include/linux/lockdep.h @@ -40,6 +40,8 @@ struct lock_class_key { struct lockdep_subclass_key subkeys[MAX_LOCKDEP_SUBCLASSES]; }; +extern struct lock_class_key __lockdep_no_validate__; + #define LOCKSTAT_POINTS 4 /* Index: usb-2.6/kernel/lockdep.c =================================================================== --- usb-2.6.orig/kernel/lockdep.c +++ usb-2.6/kernel/lockdep.c @@ -2716,6 +2716,8 @@ void lockdep_init_map(struct lockdep_map } EXPORT_SYMBOL_GPL(lockdep_init_map); +struct lock_class_key __lockdep_no_validate__; + /* * This gets called for every mutex_lock*()/spin_lock*() operation. * We maintain the dependency maps and validate the locking attempt: @@ -2750,6 +2752,9 @@ static int __lock_acquire(struct lockdep return 0; } + if (lock->key == &__lockdep_no_validate__) + check = 1; + if (!subclass) class = lock->class_cache; /* Index: usb-2.6/drivers/base/core.c =================================================================== --- usb-2.6.orig/drivers/base/core.c +++ usb-2.6/drivers/base/core.c @@ -559,6 +559,7 @@ void device_initialize(struct device *de kobject_init(&dev->kobj, &device_ktype); INIT_LIST_HEAD(&dev->dma_pools); mutex_init(&dev->mutex); + lockdep_set_class(&dev->mutex, &__lockdep_no_validate__); spin_lock_init(&dev->devres_lock); INIT_LIST_HEAD(&dev->devres_head); device_init_wakeup(dev, 0);
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