On Wed, Feb 08, 2023 at 07:17:20AM +0900, Tetsuo Handa wrote: > On 2023/02/08 2:46, Alan Stern wrote: > > The real question is what will happen in your syzbot test scenarios. > > Lockdep certainly ought to be able to detect a real deadlock when one > > occurs. It will be more interesting to find out if it can warn about > > potential deadlocks _without_ them occurring. > > For example, https://syzkaller.appspot.com/x/repro.c?x=15556074480000 generates > below warning, but I don't have syzbot environment. Please propose an updated > patch (which won't hit WARN_ON_ONCE()) for allowing people to try it in syzbot > environment. Here is a patch. I haven't tried to compile it. Alan Stern Index: usb-devel/drivers/base/core.c =================================================================== --- usb-devel.orig/drivers/base/core.c +++ usb-devel/drivers/base/core.c @@ -2322,6 +2322,9 @@ static void device_release(struct kobjec devres_release_all(dev); kfree(dev->dma_range_map); + mutex_destroy(&dev->mutex); + if (!lockdep_static_obj(dev)) + lockdep_unregister_key(&dev->mutex_key); if (dev->release) dev->release(dev); @@ -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); Index: usb-devel/include/linux/device.h =================================================================== --- usb-devel.orig/include/linux/device.h +++ usb-devel/include/linux/device.h @@ -570,6 +570,7 @@ struct device { struct mutex mutex; /* mutex to synchronize calls to * its driver. */ + struct lock_class_key mutex_key; /* Unique key for each device */ struct dev_links_info links; struct dev_pm_info power; Index: usb-devel/include/linux/lockdep.h =================================================================== --- usb-devel.orig/include/linux/lockdep.h +++ usb-devel/include/linux/lockdep.h @@ -172,6 +172,7 @@ do { \ current->lockdep_recursion -= LOCKDEP_OFF; \ } while (0) +extern int lockdep_static_obj(const void *obj); extern void lockdep_register_key(struct lock_class_key *key); extern void lockdep_unregister_key(struct lock_class_key *key); Index: usb-devel/kernel/locking/lockdep.c =================================================================== --- usb-devel.orig/kernel/locking/lockdep.c +++ usb-devel/kernel/locking/lockdep.c @@ -831,7 +831,7 @@ static int arch_is_kernel_initmem_freed( } #endif -static int static_obj(const void *obj) +int lockdep_static_obj(const void *obj) { unsigned long start = (unsigned long) &_stext, end = (unsigned long) &_end, @@ -857,6 +857,7 @@ static int static_obj(const void *obj) */ return is_module_address(addr) || is_module_percpu_address(addr); } +EXPORT_SYMBOL_GPL(lockdep_static_obj); #endif /* @@ -969,7 +970,7 @@ static bool assign_lock_key(struct lockd lock->key = (void *)can_addr; else if (__is_module_percpu_address(addr, &can_addr)) lock->key = (void *)can_addr; - else if (static_obj(lock)) + else if (lockdep_static_obj(lock)) lock->key = (void *)lock; else { /* Debug-check: all keys must be persistent! */ @@ -1220,7 +1221,7 @@ void lockdep_register_key(struct lock_cl struct lock_class_key *k; unsigned long flags; - if (WARN_ON_ONCE(static_obj(key))) + if (WARN_ON_ONCE(lockdep_static_obj(key))) return; hash_head = keyhashentry(key); @@ -1246,7 +1247,7 @@ static bool is_dynamic_key(const struct struct lock_class_key *k; bool found = false; - if (WARN_ON_ONCE(static_obj(key))) + if (WARN_ON_ONCE(lockdep_static_obj(key))) return false; /* @@ -1293,7 +1294,7 @@ register_lock_class(struct lockdep_map * if (!lock->key) { if (!assign_lock_key(lock)) return NULL; - } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) { + } else if (!lockdep_static_obj(lock->key) && !is_dynamic_key(lock->key)) { return NULL; } @@ -4836,7 +4837,7 @@ void lockdep_init_map_type(struct lockde * Sanity check, the lock-class key must either have been allocated * statically or must have been registered as a dynamic key. */ - if (!static_obj(key) && !is_dynamic_key(key)) { + if (!lockdep_static_obj(key) && !is_dynamic_key(key)) { if (debug_locks) printk(KERN_ERR "BUG: key %px has not been registered!\n", key); DEBUG_LOCKS_WARN_ON(1); @@ -6335,7 +6336,7 @@ void lockdep_unregister_key(struct lock_ might_sleep(); - if (WARN_ON_ONCE(static_obj(key))) + if (WARN_ON_ONCE(lockdep_static_obj(key))) return; raw_local_irq_save(flags);
