From 70e4506765602cca047cfa31933836e354c61a63 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 6 Dec 2006 20:40:50 -0800 Subject: [PATCH] [PATCH] lockdep: register_lock_class() fix The hash_lock must only ever be taken with irqs disabled. This happens in all the important places, except one codepath: register_lock_class(). The race should trigger rarely because register_lock_class() is quite rare and single-threaded (happens during init most of the time). The fix is to disable irqs. ( bug found live in -rt: there preemption is alot more agressive and preempting with the hash-lock held caused a lockup.) Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/lockdep.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 3926c3674354..62e73ce68197 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -1182,6 +1182,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) struct lockdep_subclass_key *key; struct list_head *hash_head; struct lock_class *class; + unsigned long flags; class = look_up_lock_class(lock, subclass); if (likely(class)) @@ -1203,6 +1204,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) key = lock->key->subkeys + subclass; hash_head = classhashentry(key); + raw_local_irq_save(flags); __raw_spin_lock(&hash_lock); /* * We have to do the hash-walk again, to avoid races @@ -1217,6 +1219,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) */ if (nr_lock_classes >= MAX_LOCKDEP_KEYS) { __raw_spin_unlock(&hash_lock); + raw_local_irq_restore(flags); debug_locks_off(); printk("BUG: MAX_LOCKDEP_KEYS too low!\n"); printk("turning off the locking correctness validator.\n"); @@ -1239,15 +1242,18 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) if (verbose(class)) { __raw_spin_unlock(&hash_lock); + raw_local_irq_restore(flags); printk("\nnew class %p: %s", class->key, class->name); if (class->name_version > 1) printk("#%d", class->name_version); printk("\n"); dump_stack(); + raw_local_irq_save(flags); __raw_spin_lock(&hash_lock); } out_unlock_set: __raw_spin_unlock(&hash_lock); + raw_local_irq_restore(flags); if (!subclass || force) lock->class_cache = class;