1 files changed, 228 insertions, 53 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index f2852a510232..298c9276dfdb 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -490,6 +490,18 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
         usage[i] = '\0';
 }
 
+static int __print_lock_name(struct lock_class *class)
+{
+        char str[KSYM_NAME_LEN];
+        const char *name;
+
+        name = class->name;
+        if (!name)
+                name = __get_key_name(class->key, str);
+
+        return printk("%s", name);
+}
+
 static void print_lock_name(struct lock_class *class)
 {
         char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
@@ -639,6 +651,16 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
         }
 #endif
 
+        if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
+                debug_locks_off();
+                printk(KERN_ERR
+                        "BUG: looking up invalid subclass: %u\n", subclass);
+                printk(KERN_ERR
+                        "turning off the locking correctness validator.\n");
+                dump_stack();
+                return NULL;
+        }
+
         /*
          * Static locks do not have their class-keys yet - for them the key
          * is the lock object itself:
@@ -774,7 +796,9 @@ out_unlock_set:
         raw_local_irq_restore(flags);
 
         if (!subclass || force)
-                lock->class_cache = class;
+                lock->class_cache[0] = class;
+        else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
+                lock->class_cache[subclass] = class;
 
         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
                 return NULL;
@@ -1041,6 +1065,56 @@ print_circular_bug_entry(struct lock_list *target, int depth)
         return 0;
 }
 
+static void
+print_circular_lock_scenario(struct held_lock *src,
+                             struct held_lock *tgt,
+                             struct lock_list *prt)
+{
+        struct lock_class *source = hlock_class(src);
+        struct lock_class *target = hlock_class(tgt);
+        struct lock_class *parent = prt->class;
+
+        /*
+         * A direct locking problem where unsafe_class lock is taken
+         * directly by safe_class lock, then all we need to show
+         * is the deadlock scenario, as it is obvious that the
+         * unsafe lock is taken under the safe lock.
+         *
+         * But if there is a chain instead, where the safe lock takes
+         * an intermediate lock (middle_class) where this lock is
+         * not the same as the safe lock, then the lock chain is
+         * used to describe the problem. Otherwise we would need
+         * to show a different CPU case for each link in the chain
+         * from the safe_class lock to the unsafe_class lock.
+         */
+        if (parent != source) {
+                printk("Chain exists of:\n  ");
+                __print_lock_name(source);
+                printk(" --> ");
+                __print_lock_name(parent);
+                printk(" --> ");
+                __print_lock_name(target);
+                printk("\n\n");
+        }
+
+        printk(" Possible unsafe locking scenario:\n\n");
+        printk("       CPU0                    CPU1\n");
+        printk("       ----                    ----\n");
+        printk("  lock(");
+        __print_lock_name(target);
+        printk(");\n");
+        printk("                               lock(");
+        __print_lock_name(parent);
+        printk(");\n");
+        printk("                               lock(");
+        __print_lock_name(target);
+        printk(");\n");
+        printk("  lock(");
+        __print_lock_name(source);
+        printk(");\n");
+        printk("\n *** DEADLOCK ***\n\n");
+}
+
 /*
  * When a circular dependency is detected, print the
  * header first:
@@ -1084,6 +1158,7 @@ static noinline int print_circular_bug(struct lock_list *this,
 {
         struct task_struct *curr = current;
         struct lock_list *parent;
+        struct lock_list *first_parent;
         int depth;
 
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
@@ -1097,6 +1172,7 @@ static noinline int print_circular_bug(struct lock_list *this,
         print_circular_bug_header(target, depth, check_src, check_tgt);
 
         parent = get_lock_parent(target);
+        first_parent = parent;
 
         while (parent) {
                 print_circular_bug_entry(parent, --depth);
@@ -1104,6 +1180,9 @@ static noinline int print_circular_bug(struct lock_list *this,
         }
 
         printk("\nother info that might help us debug this:\n\n");
+        print_circular_lock_scenario(check_src, check_tgt,
+                                     first_parent);
+
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
@@ -1302,7 +1381,7 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
                 printk("\n");
 
                 if (depth == 0 && (entry != root)) {
-                        printk("lockdep:%s bad BFS generated tree\n", __func__);
+                        printk("lockdep:%s bad path found in chain graph\n", __func__);
                         break;
                 }
 
@@ -1313,6 +1392,62 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
         return;
 }
 
+static void
+print_irq_lock_scenario(struct lock_list *safe_entry,
+                        struct lock_list *unsafe_entry,
+                        struct lock_class *prev_class,
+                        struct lock_class *next_class)
+{
+        struct lock_class *safe_class = safe_entry->class;
+        struct lock_class *unsafe_class = unsafe_entry->class;
+        struct lock_class *middle_class = prev_class;
+
+        if (middle_class == safe_class)
+                middle_class = next_class;
+
+        /*
+         * A direct locking problem where unsafe_class lock is taken
+         * directly by safe_class lock, then all we need to show
+         * is the deadlock scenario, as it is obvious that the
+         * unsafe lock is taken under the safe lock.
+         *
+         * But if there is a chain instead, where the safe lock takes
+         * an intermediate lock (middle_class) where this lock is
+         * not the same as the safe lock, then the lock chain is
+         * used to describe the problem. Otherwise we would need
+         * to show a different CPU case for each link in the chain
+         * from the safe_class lock to the unsafe_class lock.
+         */
+        if (middle_class != unsafe_class) {
+                printk("Chain exists of:\n  ");
+                __print_lock_name(safe_class);
+                printk(" --> ");
+                __print_lock_name(middle_class);
+                printk(" --> ");
+                __print_lock_name(unsafe_class);
+                printk("\n\n");
+        }
+
+        printk(" Possible interrupt unsafe locking scenario:\n\n");
+        printk("       CPU0                    CPU1\n");
+        printk("       ----                    ----\n");
+        printk("  lock(");
+        __print_lock_name(unsafe_class);
+        printk(");\n");
+        printk("                               local_irq_disable();\n");
+        printk("                               lock(");
+        __print_lock_name(safe_class);
+        printk(");\n");
+        printk("                               lock(");
+        __print_lock_name(middle_class);
+        printk(");\n");
+        printk("  <Interrupt>\n");
+        printk("    lock(");
+        __print_lock_name(safe_class);
+        printk(");\n");
+        printk("\n *** DEADLOCK ***\n\n");
+}
+
 static int
 print_bad_irq_dependency(struct task_struct *curr,
                          struct lock_list *prev_root,
@@ -1364,6 +1499,9 @@ print_bad_irq_dependency(struct task_struct *curr,
         print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
 
         printk("\nother info that might help us debug this:\n\n");
+        print_irq_lock_scenario(backwards_entry, forwards_entry,
+                                hlock_class(prev), hlock_class(next));
+
         lockdep_print_held_locks(curr);
 
         printk("\nthe dependencies between %s-irq-safe lock", irqclass);
@@ -1527,6 +1665,26 @@ static inline void inc_chains(void)
 
 #endif
 
+static void
+print_deadlock_scenario(struct held_lock *nxt,
+                             struct held_lock *prv)
+{
+        struct lock_class *next = hlock_class(nxt);
+        struct lock_class *prev = hlock_class(prv);
+
+        printk(" Possible unsafe locking scenario:\n\n");
+        printk("       CPU0\n");
+        printk("       ----\n");
+        printk("  lock(");
+        __print_lock_name(prev);
+        printk(");\n");
+        printk("  lock(");
+        __print_lock_name(next);
+        printk(");\n");
+        printk("\n *** DEADLOCK ***\n\n");
+        printk(" May be due to missing lock nesting notation\n\n");
+}
+
 static int
 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
                    struct held_lock *next)
@@ -1545,6 +1703,7 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
         print_lock(prev);
 
         printk("\nother info that might help us debug this:\n");
+        print_deadlock_scenario(next, prev);
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
@@ -1814,7 +1973,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
         struct list_head *hash_head = chainhashentry(chain_key);
         struct lock_chain *chain;
         struct held_lock *hlock_curr, *hlock_next;
-        int i, j, n, cn;
+        int i, j;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return 0;
@@ -1874,15 +2033,9 @@ cache_hit:
         }
         i++;
         chain->depth = curr->lockdep_depth + 1 - i;
-        cn = nr_chain_hlocks;
-        while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
-                n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
-                if (n == cn)
-                        break;
-                cn = n;
-        }
-        if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
-                chain->base = cn;
+        if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
+                chain->base = nr_chain_hlocks;
+                nr_chain_hlocks += chain->depth;
                 for (j = 0; j < chain->depth - 1; j++, i++) {
                         int lock_id = curr->held_locks[i].class_idx - 1;
                         chain_hlocks[chain->base + j] = lock_id;
@@ -1999,6 +2152,24 @@ static void check_chain_key(struct task_struct *curr)
 #endif
 }
 
+static void
+print_usage_bug_scenario(struct held_lock *lock)
+{
+        struct lock_class *class = hlock_class(lock);
+
+        printk(" Possible unsafe locking scenario:\n\n");
+        printk("       CPU0\n");
+        printk("       ----\n");
+        printk("  lock(");
+        __print_lock_name(class);
+        printk(");\n");
+        printk("  <Interrupt>\n");
+        printk("    lock(");
+        __print_lock_name(class);
+        printk(");\n");
+        printk("\n *** DEADLOCK ***\n\n");
+}
+
 static int
 print_usage_bug(struct task_struct *curr, struct held_lock *this,
                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
@@ -2027,6 +2198,8 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
 
         print_irqtrace_events(curr);
         printk("\nother info that might help us debug this:\n");
+        print_usage_bug_scenario(this);
+
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
@@ -2061,6 +2234,10 @@ print_irq_inversion_bug(struct task_struct *curr,
                         struct held_lock *this, int forwards,
                         const char *irqclass)
 {
+        struct lock_list *entry = other;
+        struct lock_list *middle = NULL;
+        int depth;
+
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                 return 0;
 
@@ -2079,6 +2256,25 @@ print_irq_inversion_bug(struct task_struct *curr,
         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
 
         printk("\nother info that might help us debug this:\n");
+
+        /* Find a middle lock (if one exists) */
+        depth = get_lock_depth(other);
+        do {
+                if (depth == 0 && (entry != root)) {
+                        printk("lockdep:%s bad path found in chain graph\n", __func__);
+                        break;
+                }
+                middle = entry;
+                entry = get_lock_parent(entry);
+                depth--;
+        } while (entry && entry != root && (depth >= 0));
+        if (forwards)
+                print_irq_lock_scenario(root, other,
+                        middle ? middle->class : root->class, other->class);
+        else
+                print_irq_lock_scenario(other, root,
+                        middle ? middle->class : other->class, root->class);
+
         lockdep_print_held_locks(curr);
 
         printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
@@ -2280,22 +2476,6 @@ mark_held_locks(struct task_struct *curr, enum mark_type mark)
 }
 
 /*
- * Debugging helper: via this flag we know that we are in
- * 'early bootup code', and will warn about any invalid irqs-on event:
- */
-static int early_boot_irqs_enabled;
-
-void early_boot_irqs_off(void)
-{
-        early_boot_irqs_enabled = 0;
-}
-
-void early_boot_irqs_on(void)
-{
-        early_boot_irqs_enabled = 1;
-}
-
-/*
  * Hardirqs will be enabled:
  */
 void trace_hardirqs_on_caller(unsigned long ip)
@@ -2307,13 +2487,13 @@ void trace_hardirqs_on_caller(unsigned long ip)
         if (unlikely(!debug_locks || current->lockdep_recursion))
                 return;
 
-        if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
+        if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
                 return;
 
         if (unlikely(curr->hardirqs_enabled)) {
                 /*
                  * Neither irq nor preemption are disabled here
-                 * so this is racy by nature but loosing one hit
+                 * so this is racy by nature but losing one hit
                  * in a stat is not a big deal.
                  */
                 __debug_atomic_inc(redundant_hardirqs_on);
@@ -2624,7 +2804,7 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
         if (!graph_lock())
                 return 0;
         /*
-         * Make sure we didnt race:
+         * Make sure we didn't race:
          */
         if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
                 graph_unlock();
@@ -2679,7 +2859,11 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 void lockdep_init_map(struct lockdep_map *lock, const char *name,
                       struct lock_class_key *key, int subclass)
 {
-        lock->class_cache = NULL;
+        int i;
+
+        for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+                lock->class_cache[i] = NULL;
+
 #ifdef CONFIG_LOCK_STAT
         lock->cpu = raw_smp_processor_id();
 #endif
@@ -2739,21 +2923,13 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return 0;
 
-        if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
-                debug_locks_off();
-                printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
-                printk("turning off the locking correctness validator.\n");
-                dump_stack();
-                return 0;
-        }
-
         if (lock->key == &__lockdep_no_validate__)
                 check = 1;
 
-        if (!subclass)
-                class = lock->class_cache;
+        if (subclass < NR_LOCKDEP_CACHING_CLASSES)
+                class = lock->class_cache[subclass];
         /*
-         * Not cached yet or subclass?
+         * Not cached?
          */
         if (unlikely(!class)) {
                 class = register_lock_class(lock, subclass, 0);
@@ -2918,7 +3094,7 @@ static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
                 return 1;
 
         if (hlock->references) {
-                struct lock_class *class = lock->class_cache;
+                struct lock_class *class = lock->class_cache[0];
 
                 if (!class)
                         class = look_up_lock_class(lock, 0);
@@ -3250,7 +3426,7 @@ int lock_is_held(struct lockdep_map *lock)
         int ret = 0;
 
         if (unlikely(current->lockdep_recursion))
-                return ret;
+                return 1; /* avoid false negative lockdep_assert_held() */
 
         raw_local_irq_save(flags);
         check_flags(flags);
@@ -3559,7 +3735,12 @@ void lockdep_reset_lock(struct lockdep_map *lock)
                 if (list_empty(head))
                         continue;
                 list_for_each_entry_safe(class, next, head, hash_entry) {
-                        if (unlikely(class == lock->class_cache)) {
+                        int match = 0;
+
+                        for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
+                                match |= class == lock->class_cache[j];
+
+                        if (unlikely(match)) {
                                 if (debug_locks_off_graph_unlock())
                                         WARN_ON(1);
                                 goto out_restore;
@@ -3775,7 +3956,7 @@ EXPORT_SYMBOL_GPL(debug_show_all_locks);
  * Careful: only use this function if you are sure that
  * the task cannot run in parallel!
  */
-void __debug_show_held_locks(struct task_struct *task)
+void debug_show_held_locks(struct task_struct *task)
 {
         if (unlikely(!debug_locks)) {
                 printk("INFO: lockdep is turned off.\n");
@@ -3783,12 +3964,6 @@ void __debug_show_held_locks(struct task_struct *task)
         }
         lockdep_print_held_locks(task);
 }
-EXPORT_SYMBOL_GPL(__debug_show_held_locks);
-
-void debug_show_held_locks(struct task_struct *task)
-{
-                __debug_show_held_locks(task);
-}
 EXPORT_SYMBOL_GPL(debug_show_held_locks);
 
 void lockdep_sys_exit(void)