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authorJarek Poplawski <jarkao2@o2.pl>2007-02-10 04:44:58 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-11 13:51:26 -0500
commit381a229209aa6f7f72375797b7bcfcfe2ae6fcbb (patch)
treebbd92afe1437ac77084c6ba3485f7f5a988dd673 /kernel
parent898552c9d807fe59f3ecaf9c300c109358375c12 (diff)
[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 <mingo@elte.hu> 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 <jarkao2@o2.pl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/lockdep.c23
1 files changed, 19 insertions, 4 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 509efd49540f..2d616f4d853c 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -70,6 +70,9 @@ static int graph_lock(void)
70 70
71static inline int graph_unlock(void) 71static inline int graph_unlock(void)
72{ 72{
73 if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
74 return DEBUG_LOCKS_WARN_ON(1);
75
73 __raw_spin_unlock(&lockdep_lock); 76 __raw_spin_unlock(&lockdep_lock);
74 return 0; 77 return 0;
75} 78}
@@ -712,6 +715,9 @@ find_usage_backwards(struct lock_class *source, unsigned int depth)
712 struct lock_list *entry; 715 struct lock_list *entry;
713 int ret; 716 int ret;
714 717
718 if (!__raw_spin_is_locked(&lockdep_lock))
719 return DEBUG_LOCKS_WARN_ON(1);
720
715 if (depth > max_recursion_depth) 721 if (depth > max_recursion_depth)
716 max_recursion_depth = depth; 722 max_recursion_depth = depth;
717 if (depth >= RECURSION_LIMIT) 723 if (depth >= RECURSION_LIMIT)
@@ -1293,7 +1299,8 @@ out_unlock_set:
1293 if (!subclass || force) 1299 if (!subclass || force)
1294 lock->class_cache = class; 1300 lock->class_cache = class;
1295 1301
1296 DEBUG_LOCKS_WARN_ON(class->subclass != subclass); 1302 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1303 return NULL;
1297 1304
1298 return class; 1305 return class;
1299} 1306}
@@ -1308,7 +1315,8 @@ static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class)
1308 struct list_head *hash_head = chainhashentry(chain_key); 1315 struct list_head *hash_head = chainhashentry(chain_key);
1309 struct lock_chain *chain; 1316 struct lock_chain *chain;
1310 1317
1311 DEBUG_LOCKS_WARN_ON(!irqs_disabled()); 1318 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1319 return 0;
1312 /* 1320 /*
1313 * We can walk it lock-free, because entries only get added 1321 * We can walk it lock-free, because entries only get added
1314 * to the hash: 1322 * to the hash:
@@ -1394,7 +1402,9 @@ static void check_chain_key(struct task_struct *curr)
1394 return; 1402 return;
1395 } 1403 }
1396 id = hlock->class - lock_classes; 1404 id = hlock->class - lock_classes;
1397 DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS); 1405 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1406 return;
1407
1398 if (prev_hlock && (prev_hlock->irq_context != 1408 if (prev_hlock && (prev_hlock->irq_context !=
1399 hlock->irq_context)) 1409 hlock->irq_context))
1400 chain_key = 0; 1410 chain_key = 0;
@@ -2205,7 +2215,11 @@ out_calc_hash:
2205 if (!check_prevs_add(curr, hlock)) 2215 if (!check_prevs_add(curr, hlock))
2206 return 0; 2216 return 0;
2207 graph_unlock(); 2217 graph_unlock();
2208 } 2218 } else
2219 /* after lookup_chain_cache(): */
2220 if (unlikely(!debug_locks))
2221 return 0;
2222
2209 curr->lockdep_depth++; 2223 curr->lockdep_depth++;
2210 check_chain_key(curr); 2224 check_chain_key(curr);
2211 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) { 2225 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
@@ -2214,6 +2228,7 @@ out_calc_hash:
2214 printk("turning off the locking correctness validator.\n"); 2228 printk("turning off the locking correctness validator.\n");
2215 return 0; 2229 return 0;
2216 } 2230 }
2231
2217 if (unlikely(curr->lockdep_depth > max_lockdep_depth)) 2232 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2218 max_lockdep_depth = curr->lockdep_depth; 2233 max_lockdep_depth = curr->lockdep_depth;
2219 2234