From 381a229209aa6f7f72375797b7bcfcfe2ae6fcbb Mon Sep 17 00:00:00 2001 From: Jarek Poplawski Date: Sat, 10 Feb 2007 01:44:58 -0800 Subject: [PATCH] [PATCH] lockdep: more unlock-on-error fixes - returns after DEBUG_LOCKS_WARN_ON added in 3 places - debug_locks checking after lookup_chain_cache() added in __lock_acquire() - locking for testing and changing global variable max_lockdep_depth added in __lock_acquire() From: Ingo Molnar My __acquire_lock() cleanup introduced a locking bug: on SMP systems we'd release a non-owned graph lock. Fix this by moving the graph unlock back, and by leaving the max_lockdep_depth variable update possibly racy. (we dont care, it's just statistics) Also add some minimal debugging code to graph_unlock()/graph_lock(), which caught this locking bug. Signed-off-by: Jarek Poplawski Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/lockdep.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 509efd4954..2d616f4d85 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -70,6 +70,9 @@ static int graph_lock(void) static inline int graph_unlock(void) { + if (debug_locks && !__raw_spin_is_locked(&lockdep_lock)) + return DEBUG_LOCKS_WARN_ON(1); + __raw_spin_unlock(&lockdep_lock); return 0; } @@ -712,6 +715,9 @@ find_usage_backwards(struct lock_class *source, unsigned int depth) struct lock_list *entry; int ret; + if (!__raw_spin_is_locked(&lockdep_lock)) + return DEBUG_LOCKS_WARN_ON(1); + if (depth > max_recursion_depth) max_recursion_depth = depth; if (depth >= RECURSION_LIMIT) @@ -1293,7 +1299,8 @@ out_unlock_set: if (!subclass || force) lock->class_cache = class; - DEBUG_LOCKS_WARN_ON(class->subclass != subclass); + if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass)) + return NULL; return class; } @@ -1308,7 +1315,8 @@ static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class) struct list_head *hash_head = chainhashentry(chain_key); struct lock_chain *chain; - DEBUG_LOCKS_WARN_ON(!irqs_disabled()); + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return 0; /* * We can walk it lock-free, because entries only get added * to the hash: @@ -1394,7 +1402,9 @@ static void check_chain_key(struct task_struct *curr) return; } id = hlock->class - lock_classes; - DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS); + if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)) + return; + if (prev_hlock && (prev_hlock->irq_context != hlock->irq_context)) chain_key = 0; @@ -2205,7 +2215,11 @@ out_calc_hash: if (!check_prevs_add(curr, hlock)) return 0; graph_unlock(); - } + } else + /* after lookup_chain_cache(): */ + if (unlikely(!debug_locks)) + return 0; + curr->lockdep_depth++; check_chain_key(curr); if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) { @@ -2214,6 +2228,7 @@ out_calc_hash: printk("turning off the locking correctness validator.\n"); return 0; } + if (unlikely(curr->lockdep_depth > max_lockdep_depth)) max_lockdep_depth = curr->lockdep_depth; -- 2.39.5