Cross-Referenced Linux and Device Driver Code

   /*
    * kernel/lockdep.c
    *
    * Runtime locking correctness validator
    *
    * Started by Ingo Molnar:
    *
    *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
    *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
   *
   * this code maps all the lock dependencies as they occur in a live kernel
   * and will warn about the following classes of locking bugs:
   *
   * - lock inversion scenarios
   * - circular lock dependencies
   * - hardirq/softirq safe/unsafe locking bugs
   *
   * Bugs are reported even if the current locking scenario does not cause
   * any deadlock at this point.
   *
   * I.e. if anytime in the past two locks were taken in a different order,
   * even if it happened for another task, even if those were different
   * locks (but of the same class as this lock), this code will detect it.
   *
   * Thanks to Arjan van de Ven for coming up with the initial idea of
   * mapping lock dependencies runtime.
   */
  #include <linux/mutex.h>
  #include <linux/sched.h>
  #include <linux/delay.h>
  #include <linux/module.h>
  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>
  #include <linux/spinlock.h>
  #include <linux/kallsyms.h>
  #include <linux/interrupt.h>
  #include <linux/stacktrace.h>
  #include <linux/debug_locks.h>
  #include <linux/irqflags.h>
  #include <linux/utsname.h>
  #include <linux/hash.h>
  #include <linux/ftrace.h>
  
  #include <asm/sections.h>
  
  #include "lockdep_internals.h"
  
  #ifdef CONFIG_PROVE_LOCKING
  int prove_locking = 1;
  module_param(prove_locking, int, 0644);
  #else
  #define prove_locking 0
  #endif
  
  #ifdef CONFIG_LOCK_STAT
  int lock_stat = 1;
  module_param(lock_stat, int, 0644);
  #else
  #define lock_stat 0
  #endif
  
  /*
   * lockdep_lock: protects the lockdep graph, the hashes and the
   *               class/list/hash allocators.
   *
   * This is one of the rare exceptions where it's justified
   * to use a raw spinlock - we really dont want the spinlock
   * code to recurse back into the lockdep code...
   */
  static __raw_spinlock_t lockdep_lock = (__raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
  
  static int graph_lock(void)
  {
          __raw_spin_lock(&lockdep_lock);
          /*
           * Make sure that if another CPU detected a bug while
           * walking the graph we dont change it (while the other
           * CPU is busy printing out stuff with the graph lock
           * dropped already)
           */
          if (!debug_locks) {
                  __raw_spin_unlock(&lockdep_lock);
                  return 0;
          }
          /* prevent any recursions within lockdep from causing deadlocks */
          current->lockdep_recursion++;
          return 1;
  }
  
  static inline int graph_unlock(void)
  {
          if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
                  return DEBUG_LOCKS_WARN_ON(1);
  
          current->lockdep_recursion--;
          __raw_spin_unlock(&lockdep_lock);
          return 0;
  }
  
 /*
  * Turn lock debugging off and return with 0 if it was off already,
  * and also release the graph lock:
  */
 static inline int debug_locks_off_graph_unlock(void)
 {
         int ret = debug_locks_off();
 
         __raw_spin_unlock(&lockdep_lock);
 
         return ret;
 }
 
 static int lockdep_initialized;
 
 unsigned long nr_list_entries;
 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 
 /*
  * All data structures here are protected by the global debug_lock.
  *
  * Mutex key structs only get allocated, once during bootup, and never
  * get freed - this significantly simplifies the debugging code.
  */
 unsigned long nr_lock_classes;
 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 
 #ifdef CONFIG_LOCK_STAT
 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
 
 static int lock_contention_point(struct lock_class *class, unsigned long ip)
 {
         int i;
 
         for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
                 if (class->contention_point[i] == 0) {
                         class->contention_point[i] = ip;
                         break;
                 }
                 if (class->contention_point[i] == ip)
                         break;
         }
 
         return i;
 }
 
 static void lock_time_inc(struct lock_time *lt, s64 time)
 {
         if (time > lt->max)
                 lt->max = time;
 
         if (time < lt->min || !lt->min)
                 lt->min = time;
 
         lt->total += time;
         lt->nr++;
 }
 
 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
 {
         dst->min += src->min;
         dst->max += src->max;
         dst->total += src->total;
         dst->nr += src->nr;
 }
 
 struct lock_class_stats lock_stats(struct lock_class *class)
 {
         struct lock_class_stats stats;
         int cpu, i;
 
         memset(&stats, 0, sizeof(struct lock_class_stats));
         for_each_possible_cpu(cpu) {
                 struct lock_class_stats *pcs =
                         &per_cpu(lock_stats, cpu)[class - lock_classes];
 
                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
                         stats.contention_point[i] += pcs->contention_point[i];
 
                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
 
                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
 
                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
                         stats.bounces[i] += pcs->bounces[i];
         }
 
         return stats;
 }
 
 void clear_lock_stats(struct lock_class *class)
 {
         int cpu;
 
         for_each_possible_cpu(cpu) {
                 struct lock_class_stats *cpu_stats =
                         &per_cpu(lock_stats, cpu)[class - lock_classes];
 
                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
         }
         memset(class->contention_point, 0, sizeof(class->contention_point));
 }
 
 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 {
         return &get_cpu_var(lock_stats)[class - lock_classes];
 }
 
 static void put_lock_stats(struct lock_class_stats *stats)
 {
         put_cpu_var(lock_stats);
 }
 
 static void lock_release_holdtime(struct held_lock *hlock)
 {
         struct lock_class_stats *stats;
         s64 holdtime;
 
         if (!lock_stat)
                 return;
 
         holdtime = sched_clock() - hlock->holdtime_stamp;
 
         stats = get_lock_stats(hlock->class);
         if (hlock->read)
                 lock_time_inc(&stats->read_holdtime, holdtime);
         else
                 lock_time_inc(&stats->write_holdtime, holdtime);
         put_lock_stats(stats);
 }
 #else
 static inline void lock_release_holdtime(struct held_lock *hlock)
 {
 }
 #endif
 
 /*
  * We keep a global list of all lock classes. The list only grows,
  * never shrinks. The list is only accessed with the lockdep
  * spinlock lock held.
  */
 LIST_HEAD(all_lock_classes);
 
 /*
  * The lockdep classes are in a hash-table as well, for fast lookup:
  */
 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
 
 static struct list_head classhash_table[CLASSHASH_SIZE];
 
 /*
  * We put the lock dependency chains into a hash-table as well, to cache
  * their existence:
  */
 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
 
 static struct list_head chainhash_table[CHAINHASH_SIZE];
 
 /*
  * The hash key of the lock dependency chains is a hash itself too:
  * it's a hash of all locks taken up to that lock, including that lock.
  * It's a 64-bit hash, because it's important for the keys to be
  * unique.
  */
 #define iterate_chain_key(key1, key2) \
         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
         (key2))
 
 void lockdep_off(void)
 {
         current->lockdep_recursion++;
 }
 
 EXPORT_SYMBOL(lockdep_off);
 
 void lockdep_on(void)
 {
         current->lockdep_recursion--;
 }
 
 EXPORT_SYMBOL(lockdep_on);
 
 /*
  * Debugging switches:
  */
 
 #define VERBOSE                 0
 #define VERY_VERBOSE            0
 
 #if VERBOSE
 # define HARDIRQ_VERBOSE        1
 # define SOFTIRQ_VERBOSE        1
 #else
 # define HARDIRQ_VERBOSE        0
 # define SOFTIRQ_VERBOSE        0
 #endif
 
 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
 /*
  * Quick filtering for interesting events:
  */
 static int class_filter(struct lock_class *class)
 {
 #if 0
         /* Example */
         if (class->name_version == 1 &&
                         !strcmp(class->name, "lockname"))
                 return 1;
         if (class->name_version == 1 &&
                         !strcmp(class->name, "&struct->lockfield"))
                 return 1;
 #endif
         /* Filter everything else. 1 would be to allow everything else */
         return 0;
 }
 #endif
 
 static int verbose(struct lock_class *class)
 {
 #if VERBOSE
         return class_filter(class);
 #endif
         return 0;
 }
 
 /*
  * Stack-trace: tightly packed array of stack backtrace
  * addresses. Protected by the graph_lock.
  */
 unsigned long nr_stack_trace_entries;
 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
 
 static int save_trace(struct stack_trace *trace)
 {
         trace->nr_entries = 0;
         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
         trace->entries = stack_trace + nr_stack_trace_entries;
 
         trace->skip = 3;
 
         save_stack_trace(trace);
 
         trace->max_entries = trace->nr_entries;
 
         nr_stack_trace_entries += trace->nr_entries;
 
         if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
                 if (!debug_locks_off_graph_unlock())
                         return 0;
 
                 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
                 printk("turning off the locking correctness validator.\n");
                 dump_stack();
 
                 return 0;
         }
 
         return 1;
 }
 
 unsigned int nr_hardirq_chains;
 unsigned int nr_softirq_chains;
 unsigned int nr_process_chains;
 unsigned int max_lockdep_depth;
 unsigned int max_recursion_depth;
 
 #ifdef CONFIG_DEBUG_LOCKDEP
 /*
  * We cannot printk in early bootup code. Not even early_printk()
  * might work. So we mark any initialization errors and printk
  * about it later on, in lockdep_info().
  */
 static int lockdep_init_error;
 static unsigned long lockdep_init_trace_data[20];
 static struct stack_trace lockdep_init_trace = {
         .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
         .entries = lockdep_init_trace_data,
 };
 
 /*
  * Various lockdep statistics:
  */
 atomic_t chain_lookup_hits;
 atomic_t chain_lookup_misses;
 atomic_t hardirqs_on_events;
 atomic_t hardirqs_off_events;
 atomic_t redundant_hardirqs_on;
 atomic_t redundant_hardirqs_off;
 atomic_t softirqs_on_events;
 atomic_t softirqs_off_events;
 atomic_t redundant_softirqs_on;
 atomic_t redundant_softirqs_off;
 atomic_t nr_unused_locks;
 atomic_t nr_cyclic_checks;
 atomic_t nr_cyclic_check_recursions;
 atomic_t nr_find_usage_forwards_checks;
 atomic_t nr_find_usage_forwards_recursions;
 atomic_t nr_find_usage_backwards_checks;
 atomic_t nr_find_usage_backwards_recursions;
 # define debug_atomic_inc(ptr)          atomic_inc(ptr)
 # define debug_atomic_dec(ptr)          atomic_dec(ptr)
 # define debug_atomic_read(ptr)         atomic_read(ptr)
 #else
 # define debug_atomic_inc(ptr)          do { } while (0)
 # define debug_atomic_dec(ptr)          do { } while (0)
 # define debug_atomic_read(ptr)         0
 #endif
 
 /*
  * Locking printouts:
  */
 
 static const char *usage_str[] =
 {
         [LOCK_USED] =                   "initial-use ",
         [LOCK_USED_IN_HARDIRQ] =        "in-hardirq-W",
         [LOCK_USED_IN_SOFTIRQ] =        "in-softirq-W",
         [LOCK_ENABLED_SOFTIRQS] =       "softirq-on-W",
         [LOCK_ENABLED_HARDIRQS] =       "hardirq-on-W",
         [LOCK_USED_IN_HARDIRQ_READ] =   "in-hardirq-R",
         [LOCK_USED_IN_SOFTIRQ_READ] =   "in-softirq-R",
         [LOCK_ENABLED_SOFTIRQS_READ] =  "softirq-on-R",
         [LOCK_ENABLED_HARDIRQS_READ] =  "hardirq-on-R",
 };
 
 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
 {
         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
 }
 
 void
 get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4)
 {
         *c1 = '.', *c2 = '.', *c3 = '.', *c4 = '.';
 
         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
                 *c1 = '+';
         else
                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
                         *c1 = '-';
 
         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
                 *c2 = '+';
         else
                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
                         *c2 = '-';
 
         if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
                 *c3 = '-';
         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ) {
                 *c3 = '+';
                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
                         *c3 = '?';
         }
 
         if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
                 *c4 = '-';
         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ) {
                 *c4 = '+';
                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
                         *c4 = '?';
         }
 }
 
 static void print_lock_name(struct lock_class *class)
 {
         char str[KSYM_NAME_LEN], c1, c2, c3, c4;
         const char *name;
 
         get_usage_chars(class, &c1, &c2, &c3, &c4);
 
         name = class->name;
         if (!name) {
                 name = __get_key_name(class->key, str);
                 printk(" (%s", name);
         } else {
                 printk(" (%s", name);
                 if (class->name_version > 1)
                         printk("#%d", class->name_version);
                 if (class->subclass)
                         printk("/%d", class->subclass);
         }
         printk("){%c%c%c%c}", c1, c2, c3, c4);
 }
 
 static void print_lockdep_cache(struct lockdep_map *lock)
 {
         const char *name;
         char str[KSYM_NAME_LEN];
 
         name = lock->name;
         if (!name)
                 name = __get_key_name(lock->key->subkeys, str);
 
         printk("%s", name);
 }
 
 static void print_lock(struct held_lock *hlock)
 {
         print_lock_name(hlock->class);
         printk(", at: ");
         print_ip_sym(hlock->acquire_ip);
 }
 
 static void lockdep_print_held_locks(struct task_struct *curr)
 {
         int i, depth;
 
         if (!curr)
                 curr = current;
         depth = curr->lockdep_depth;
 
         if (!depth) {
                 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
                 return;
         }
         printk("%d lock%s held by %s/%d:\n",
                 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
 
         for (i = 0; i < depth; i++) {
                 printk(" #%d: ", i);
                 print_lock(curr->held_locks + i);
         }
 }
 
 static void print_lock_class_header(struct lock_class *class, int depth)
 {
         int bit;
 
         printk("%*s->", depth, "");
         print_lock_name(class);
         printk(" ops: %lu", class->ops);
         printk(" {\n");
 
         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
                 if (class->usage_mask & (1 << bit)) {
                         int len = depth;
 
                         len += printk("%*s   %s", depth, "", usage_str[bit]);
                         len += printk(" at:\n");
                         print_stack_trace(class->usage_traces + bit, len);
                 }
         }
         printk("%*s }\n", depth, "");
 
         printk("%*s ... key      at: ",depth,"");
         print_ip_sym((unsigned long)class->key);
 }
 
 /*
  * printk all lock dependencies starting at <entry>:
  */
 static void print_lock_dependencies(struct lock_class *class, int depth)
 {
         struct lock_list *entry;
 
         if (DEBUG_LOCKS_WARN_ON(depth >= 20))
                 return;
 
         print_lock_class_header(class, depth);
 
         list_for_each_entry(entry, &class->locks_after, entry) {
                 if (DEBUG_LOCKS_WARN_ON(!entry->class))
                         return;
 
                 print_lock_dependencies(entry->class, depth + 1);
 
                 printk("%*s ... acquired at:\n",depth,"");
                 print_stack_trace(&entry->trace, 2);
                 printk("\n");
         }
 }
 
 static void print_kernel_version(void)
 {
         printk("[ %s %.*s\n", init_utsname()->release,
                 (int)strcspn(init_utsname()->version, " "),
                 init_utsname()->version);
 }
 
 static int very_verbose(struct lock_class *class)
 {
 #if VERY_VERBOSE
         return class_filter(class);
 #endif
         return 0;
 }
 
 /*
  * Is this the address of a static object:
  */
 static int static_obj(void *obj)
 {
         unsigned long start = (unsigned long) &_stext,
                       end   = (unsigned long) &_end,
                       addr  = (unsigned long) obj;
 #ifdef CONFIG_SMP
         int i;
 #endif
 
         /*
          * static variable?
          */
         if ((addr >= start) && (addr < end))
                 return 1;
 
 #ifdef CONFIG_SMP
         /*
          * percpu var?
          */
         for_each_possible_cpu(i) {
                 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
                 end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
                                         + per_cpu_offset(i);
 
                 if ((addr >= start) && (addr < end))
                         return 1;
         }
 #endif
 
         /*
          * module var?
          */
         return is_module_address(addr);
 }
 
 /*
  * To make lock name printouts unique, we calculate a unique
  * class->name_version generation counter:
  */
 static int count_matching_names(struct lock_class *new_class)
 {
         struct lock_class *class;
         int count = 0;
 
         if (!new_class->name)
                 return 0;
 
         list_for_each_entry(class, &all_lock_classes, lock_entry) {
                 if (new_class->key - new_class->subclass == class->key)
                         return class->name_version;
                 if (class->name && !strcmp(class->name, new_class->name))
                         count = max(count, class->name_version);
         }
 
         return count + 1;
 }
 
 /*
  * Register a lock's class in the hash-table, if the class is not present
  * yet. Otherwise we look it up. We cache the result in the lock object
  * itself, so actual lookup of the hash should be once per lock object.
  */
 static inline struct lock_class *
 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 {
         struct lockdep_subclass_key *key;
         struct list_head *hash_head;
         struct lock_class *class;
 
 #ifdef CONFIG_DEBUG_LOCKDEP
         /*
          * If the architecture calls into lockdep before initializing
          * the hashes then we'll warn about it later. (we cannot printk
          * right now)
          */
         if (unlikely(!lockdep_initialized)) {
                 lockdep_init();
                 lockdep_init_error = 1;
                 save_stack_trace(&lockdep_init_trace);
         }
 #endif
 
         /*
          * Static locks do not have their class-keys yet - for them the key
          * is the lock object itself:
          */
         if (unlikely(!lock->key))
                 lock->key = (void *)lock;
 
         /*
          * NOTE: the class-key must be unique. For dynamic locks, a static
          * lock_class_key variable is passed in through the mutex_init()
          * (or spin_lock_init()) call - which acts as the key. For static
          * locks we use the lock object itself as the key.
          */
         BUILD_BUG_ON(sizeof(struct lock_class_key) >
                         sizeof(struct lockdep_map));
 
         key = lock->key->subkeys + subclass;
 
         hash_head = classhashentry(key);
 
         /*
          * We can walk the hash lockfree, because the hash only
          * grows, and we are careful when adding entries to the end:
          */
         list_for_each_entry(class, hash_head, hash_entry) {
                 if (class->key == key) {
                         WARN_ON_ONCE(class->name != lock->name);
                         return class;
                 }
         }
 
         return NULL;
 }
 
 /*
  * Register a lock's class in the hash-table, if the class is not present
  * yet. Otherwise we look it up. We cache the result in the lock object
  * itself, so actual lookup of the hash should be once per lock object.
  */
 static inline struct lock_class *
 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))
                 return class;
 
         /*
          * Debug-check: all keys must be persistent!
          */
         if (!static_obj(lock->key)) {
                 debug_locks_off();
                 printk("INFO: trying to register non-static key.\n");
                 printk("the code is fine but needs lockdep annotation.\n");
                 printk("turning off the locking correctness validator.\n");
                 dump_stack();
 
                 return NULL;
         }
 
         key = lock->key->subkeys + subclass;
         hash_head = classhashentry(key);
 
         raw_local_irq_save(flags);
         if (!graph_lock()) {
                 raw_local_irq_restore(flags);
                 return NULL;
         }
         /*
          * We have to do the hash-walk again, to avoid races
          * with another CPU:
          */
         list_for_each_entry(class, hash_head, hash_entry)
                 if (class->key == key)
                         goto out_unlock_set;
         /*
          * Allocate a new key from the static array, and add it to
          * the hash:
          */
         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
                 if (!debug_locks_off_graph_unlock()) {
                         raw_local_irq_restore(flags);
                         return NULL;
                 }
                 raw_local_irq_restore(flags);
 
                 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
                 printk("turning off the locking correctness validator.\n");
                 return NULL;
         }
         class = lock_classes + nr_lock_classes++;
         debug_atomic_inc(&nr_unused_locks);
         class->key = key;
         class->name = lock->name;
         class->subclass = subclass;
         INIT_LIST_HEAD(&class->lock_entry);
         INIT_LIST_HEAD(&class->locks_before);
         INIT_LIST_HEAD(&class->locks_after);
         class->name_version = count_matching_names(class);
         /*
          * We use RCU's safe list-add method to make
          * parallel walking of the hash-list safe:
          */
         list_add_tail_rcu(&class->hash_entry, hash_head);
         /*
          * Add it to the global list of classes:
          */
         list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
 
         if (verbose(class)) {
                 graph_unlock();
                 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);
                 if (!graph_lock()) {
                         raw_local_irq_restore(flags);
                         return NULL;
                 }
         }
 out_unlock_set:
         graph_unlock();
         raw_local_irq_restore(flags);
 
         if (!subclass || force)
                 lock->class_cache = class;
 
         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
                 return NULL;
 
         return class;
 }
 
 #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_TRACE_IRQFLAGS)
 
 #define RECURSION_LIMIT 40
 
 static int noinline print_infinite_recursion_bug(void)
 {
         if (!debug_locks_off_graph_unlock())
                 return 0;
 
         WARN_ON(1);
 
         return 0;
 }
 #endif /* CONFIG_PROVE_LOCKING || CONFIG_TRACE_IRQFLAGS */
 
 #ifdef CONFIG_PROVE_LOCKING
 /*
  * Allocate a lockdep entry. (assumes the graph_lock held, returns
  * with NULL on failure)
  */
 static struct lock_list *alloc_list_entry(void)
 {
         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
                 if (!debug_locks_off_graph_unlock())
                         return NULL;
 
                 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
                 printk("turning off the locking correctness validator.\n");
                 return NULL;
         }
         return list_entries + nr_list_entries++;
 }
 
 /*
  * Add a new dependency to the head of the list:
  */
 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
                             struct list_head *head, unsigned long ip, int distance)
 {
         struct lock_list *entry;
         /*
          * Lock not present yet - get a new dependency struct and
          * add it to the list:
          */
         entry = alloc_list_entry();
         if (!entry)
                 return 0;
 
         entry->class = this;
         entry->distance = distance;
         if (!save_trace(&entry->trace))
                 return 0;
 
         /*
          * Since we never remove from the dependency list, the list can
          * be walked lockless by other CPUs, it's only allocation
          * that must be protected by the spinlock. But this also means
          * we must make new entries visible only once writes to the
          * entry become visible - hence the RCU op:
          */
         list_add_tail_rcu(&entry->entry, head);
 
         return 1;
 }
 
 /*
  * Recursive, forwards-direction lock-dependency checking, used for
  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
  * checking.
  *
  * (to keep the stackframe of the recursive functions small we
  *  use these global variables, and we also mark various helper
  *  functions as noinline.)
  */
 static struct held_lock *check_source, *check_target;
 
 /*
  * Print a dependency chain entry (this is only done when a deadlock
  * has been detected):
  */
 static noinline int
 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
 {
         if (debug_locks_silent)
                 return 0;
         printk("\n-> #%u", depth);
         print_lock_name(target->class);
         printk(":\n");
         print_stack_trace(&target->trace, 6);
 
         return 0;
 }
 
 /*
  * When a circular dependency is detected, print the
  * header first:
  */
 static noinline int
 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
 {
         struct task_struct *curr = current;
 
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                 return 0;
 
         printk("\n=======================================================\n");
         printk(  "[ INFO: possible circular locking dependency detected ]\n");
         print_kernel_version();
         printk(  "-------------------------------------------------------\n");
         printk("%s/%d is trying to acquire lock:\n",
                 curr->comm, task_pid_nr(curr));
         print_lock(check_source);
         printk("\nbut task is already holding lock:\n");
         print_lock(check_target);
         printk("\nwhich lock already depends on the new lock.\n\n");
         printk("\nthe existing dependency chain (in reverse order) is:\n");
 
         print_circular_bug_entry(entry, depth);
 
         return 0;
 }
 
 static noinline int print_circular_bug_tail(void)
 {
         struct task_struct *curr = current;
         struct lock_list this;
 
         if (debug_locks_silent)
                 return 0;
 
         this.class = check_source->class;
         if (!save_trace(&this.trace))
                 return 0;
 
         print_circular_bug_entry(&this, 0);
 
         printk("\nother info that might help us debug this:\n\n");
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 
 /*
  * Prove that the dependency graph starting at <entry> can not
  * lead to <target>. Print an error and return 0 if it does.
  */
 static noinline int
 check_noncircular(struct lock_class *source, unsigned int depth)
 {
         struct lock_list *entry;
 
         debug_atomic_inc(&nr_cyclic_check_recursions);
         if (depth > max_recursion_depth)
                 max_recursion_depth = depth;
         if (depth >= RECURSION_LIMIT)
                 return print_infinite_recursion_bug();
         /*
          * Check this lock's dependency list:
          */
         list_for_each_entry(entry, &source->locks_after, entry) {
                 if (entry->class == check_target->class)
                         return print_circular_bug_header(entry, depth+1);
                 debug_atomic_inc(&nr_cyclic_checks);
                 if (!check_noncircular(entry->class, depth+1))
                         return print_circular_bug_entry(entry, depth+1);
         }
         return 1;
 }
 
 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
 /*
  * Forwards and backwards subgraph searching, for the purposes of
  * proving that two subgraphs can be connected by a new dependency
  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
  */
 static enum lock_usage_bit find_usage_bit;
 static struct lock_class *forwards_match, *backwards_match;
 
 /*
  * Find a node in the forwards-direction dependency sub-graph starting
  * at <source> that matches <find_usage_bit>.
  *
  * Return 2 if such a node exists in the subgraph, and put that node
  * into <forwards_match>.
  *
  * Return 1 otherwise and keep <forwards_match> unchanged.
  * Return 0 on error.
  */
 static noinline int
 find_usage_forwards(struct lock_class *source, unsigned int depth)
 {
         struct lock_list *entry;
         int ret;
 
         if (depth > max_recursion_depth)
                 max_recursion_depth = depth;
         if (depth >= RECURSION_LIMIT)
                 return print_infinite_recursion_bug();
 
         debug_atomic_inc(&nr_find_usage_forwards_checks);
         if (source->usage_mask & (1 << find_usage_bit)) {
                 forwards_match = source;
                 return 2;
         }
 
         /*
          * Check this lock's dependency list:
          */
         list_for_each_entry(entry, &source->locks_after, entry) {
                 debug_atomic_inc(&nr_find_usage_forwards_recursions);
                 ret = find_usage_forwards(entry->class, depth+1);
                 if (ret == 2 || ret == 0)
                         return ret;
         }
         return 1;
 }
 
 /*
  * Find a node in the backwards-direction dependency sub-graph starting
  * at <source> that matches <find_usage_bit>.
  *
  * Return 2 if such a node exists in the subgraph, and put that node
  * into <backwards_match>.
  *
  * Return 1 otherwise and keep <backwards_match> unchanged.
  * Return 0 on error.
  */
 static noinline int
 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)
                 return print_infinite_recursion_bug();
 
         debug_atomic_inc(&nr_find_usage_backwards_checks);
         if (source->usage_mask & (1 << find_usage_bit)) {
                 backwards_match = source;
                 return 2;
         }
 
         /*
          * Check this lock's dependency list:
          */
         list_for_each_entry(entry, &source->locks_before, entry) {
                 debug_atomic_inc(&nr_find_usage_backwards_recursions);
                 ret = find_usage_backwards(entry->class, depth+1);
                 if (ret == 2 || ret == 0)
                         return ret;
         }
         return 1;
 }
 
 #ifdef CONFIG_PROVE_LOCKING
 static int
 print_bad_irq_dependency(struct task_struct *curr,
                          struct held_lock *prev,
                          struct held_lock *next,
                          enum lock_usage_bit bit1,
                          enum lock_usage_bit bit2,
                          const char *irqclass)
 {
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                 return 0;
 
         printk("\n======================================================\n");
         printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
                 irqclass, irqclass);
         print_kernel_version();
         printk(  "------------------------------------------------------\n");
         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
                 curr->comm, task_pid_nr(curr),
                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
                 curr->hardirqs_enabled,
                 curr->softirqs_enabled);
         print_lock(next);
 
         printk("\nand this task is already holding:\n");
         print_lock(prev);
         printk("which would create a new lock dependency:\n");
         print_lock_name(prev->class);
         printk(" ->");
         print_lock_name(next->class);
         printk("\n");
 
         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
                 irqclass);
         print_lock_name(backwards_match);
         printk("\n... which became %s-irq-safe at:\n", irqclass);
 
         print_stack_trace(backwards_match->usage_traces + bit1, 1);
 
         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
         print_lock_name(forwards_match);
         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
         printk("...");
 
         print_stack_trace(forwards_match->usage_traces + bit2, 1);
 
         printk("\nother info that might help us debug this:\n\n");
         lockdep_print_held_locks(curr);
 
         printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
         print_lock_dependencies(backwards_match, 0);
 
         printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
         print_lock_dependencies(forwards_match, 0);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 #endif /* CONFIG_PROVE_LOCKING */
 
 static int
 check_usage(struct task_struct *curr, struct held_lock *prev,
             struct held_lock *next, enum lock_usage_bit bit_backwards,
             enum lock_usage_bit bit_forwards, const char *irqclass)
 {
         int ret;
 
         find_usage_bit = bit_backwards;
         /* fills in <backwards_match> */
         ret = find_usage_backwards(prev->class, 0);
         if (!ret || ret == 1)
                 return ret;
 
         find_usage_bit = bit_forwards;
         ret = find_usage_forwards(next->class, 0);
         if (!ret || ret == 1)
                 return ret;
         /* ret == 2 */
         return print_bad_irq_dependency(curr, prev, next,
                         bit_backwards, bit_forwards, irqclass);
 }
 
 static int
 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
                 struct held_lock *next)
 {
         /*
          * Prove that the new dependency does not connect a hardirq-safe
          * lock with a hardirq-unsafe lock - to achieve this we search
          * the backwards-subgraph starting at <prev>, and the
          * forwards-subgraph starting at <next>:
          */
         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ,
                                         LOCK_ENABLED_HARDIRQS, "hard"))
                 return 0;
 
         /*
          * Prove that the new dependency does not connect a hardirq-safe-read
          * lock with a hardirq-unsafe lock - to achieve this we search
          * the backwards-subgraph starting at <prev>, and the
          * forwards-subgraph starting at <next>:
          */
         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ_READ,
                                         LOCK_ENABLED_HARDIRQS, "hard-read"))
                 return 0;
 
         /*
          * Prove that the new dependency does not connect a softirq-safe
          * lock with a softirq-unsafe lock - to achieve this we search
          * the backwards-subgraph starting at <prev>, and the
          * forwards-subgraph starting at <next>:
          */
         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ,
                                         LOCK_ENABLED_SOFTIRQS, "soft"))
                 return 0;
         /*
          * Prove that the new dependency does not connect a softirq-safe-read
          * lock with a softirq-unsafe lock - to achieve this we search
          * the backwards-subgraph starting at <prev>, and the
          * forwards-subgraph starting at <next>:
          */
         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ_READ,
                                         LOCK_ENABLED_SOFTIRQS, "soft"))
                 return 0;
 
         return 1;
 }
 
 static void inc_chains(void)
 {
         if (current->hardirq_context)
                 nr_hardirq_chains++;
         else {
                 if (current->softirq_context)
                         nr_softirq_chains++;
                 else
                         nr_process_chains++;
         }
 }
 
 #else
 
 static inline int
 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
                 struct held_lock *next)
 {
         return 1;
 }
 
 static inline void inc_chains(void)
 {
         nr_process_chains++;
 }
 
 #endif
 
 static int
 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
                    struct held_lock *next)
 {
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                 return 0;
 
         printk("\n=============================================\n");
         printk(  "[ INFO: possible recursive locking detected ]\n");
         print_kernel_version();
         printk(  "---------------------------------------------\n");
         printk("%s/%d is trying to acquire lock:\n",
                 curr->comm, task_pid_nr(curr));
         print_lock(next);
         printk("\nbut task is already holding lock:\n");
         print_lock(prev);
 
         printk("\nother info that might help us debug this:\n");
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 
 /*
  * Check whether we are holding such a class already.
  *
  * (Note that this has to be done separately, because the graph cannot
  * detect such classes of deadlocks.)
  *
  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
  */
 static int
 check_deadlock(struct task_struct *curr, struct held_lock *next,
                struct lockdep_map *next_instance, int read)
 {
         struct held_lock *prev;
         int i;
 
         for (i = 0; i < curr->lockdep_depth; i++) {
                 prev = curr->held_locks + i;
                 if (prev->class != next->class)
                         continue;
                 /*
                  * Allow read-after-read recursion of the same
                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
                  */
                 if ((read == 2) && prev->read)
                         return 2;
                 return print_deadlock_bug(curr, prev, next);
         }
         return 1;
 }
 
 /*
  * There was a chain-cache miss, and we are about to add a new dependency
  * to a previous lock. We recursively validate the following rules:
  *
  *  - would the adding of the <prev> -> <next> dependency create a
  *    circular dependency in the graph? [== circular deadlock]
  *
  *  - does the new prev->next dependency connect any hardirq-safe lock
  *    (in the full backwards-subgraph starting at <prev>) with any
  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
  *    <next>)? [== illegal lock inversion with hardirq contexts]
  *
  *  - does the new prev->next dependency connect any softirq-safe lock
  *    (in the full backwards-subgraph starting at <prev>) with any
  *    softirq-unsafe lock (in the full forwards-subgraph starting at
  *    <next>)? [== illegal lock inversion with softirq contexts]
  *
  * any of these scenarios could lead to a deadlock.
  *
  * Then if all the validations pass, we add the forwards and backwards
  * dependency.
  */
 static int
 check_prev_add(struct task_struct *curr, struct held_lock *prev,
                struct held_lock *next, int distance)
 {
         struct lock_list *entry;
         int ret;
 
         /*
          * Prove that the new <prev> -> <next> dependency would not
          * create a circular dependency in the graph. (We do this by
          * forward-recursing into the graph starting at <next>, and
          * checking whether we can reach <prev>.)
          *
          * We are using global variables to control the recursion, to
          * keep the stackframe size of the recursive functions low:
          */
         check_source = next;
         check_target = prev;
         if (!(check_noncircular(next->class, 0)))
                 return print_circular_bug_tail();
 
         if (!check_prev_add_irq(curr, prev, next))
                 return 0;
 
         /*
          * For recursive read-locks we do all the dependency checks,
          * but we dont store read-triggered dependencies (only
          * write-triggered dependencies). This ensures that only the
          * write-side dependencies matter, and that if for example a
          * write-lock never takes any other locks, then the reads are
          * equivalent to a NOP.
          */
         if (next->read == 2 || prev->read == 2)
                 return 1;
         /*
          * Is the <prev> -> <next> dependency already present?
          *
          * (this may occur even though this is a new chain: consider
          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
          *  chains - the second one will be new, but L1 already has
          *  L2 added to its dependency list, due to the first chain.)
          */
         list_for_each_entry(entry, &prev->class->locks_after, entry) {
                 if (entry->class == next->class) {
                         if (distance == 1)
                                 entry->distance = 1;
                         return 2;
                 }
         }
 
         /*
          * Ok, all validations passed, add the new lock
          * to the previous lock's dependency list:
          */
         ret = add_lock_to_list(prev->class, next->class,
                                &prev->class->locks_after, next->acquire_ip, distance);
 
         if (!ret)
                 return 0;
 
         ret = add_lock_to_list(next->class, prev->class,
                                &next->class->locks_before, next->acquire_ip, distance);
         if (!ret)
                 return 0;
 
         /*
          * Debugging printouts:
          */
         if (verbose(prev->class) || verbose(next->class)) {
                 graph_unlock();
                 printk("\n new dependency: ");
                 print_lock_name(prev->class);
                 printk(" => ");
                 print_lock_name(next->class);
                 printk("\n");
                 dump_stack();
                 return graph_lock();
         }
         return 1;
 }
 
 /*
  * Add the dependency to all directly-previous locks that are 'relevant'.
  * The ones that are relevant are (in increasing distance from curr):
  * all consecutive trylock entries and the final non-trylock entry - or
  * the end of this context's lock-chain - whichever comes first.
  */
 static int
 check_prevs_add(struct task_struct *curr, struct held_lock *next)
 {
         int depth = curr->lockdep_depth;
         struct held_lock *hlock;
 
         /*
          * Debugging checks.
          *
          * Depth must not be zero for a non-head lock:
          */
         if (!depth)
                 goto out_bug;
         /*
          * At least two relevant locks must exist for this
          * to be a head:
          */
         if (curr->held_locks[depth].irq_context !=
                         curr->held_locks[depth-1].irq_context)
                 goto out_bug;
 
         for (;;) {
                 int distance = curr->lockdep_depth - depth + 1;
                 hlock = curr->held_locks + depth-1;
                 /*
                  * Only non-recursive-read entries get new dependencies
                  * added:
                  */
                 if (hlock->read != 2) {
                         if (!check_prev_add(curr, hlock, next, distance))
                                 return 0;
                         /*
                          * Stop after the first non-trylock entry,
                          * as non-trylock entries have added their
                          * own direct dependencies already, so this
                          * lock is connected to them indirectly:
                          */
                         if (!hlock->trylock)
                                 break;
                 }
                 depth--;
                 /*
                  * End of lock-stack?
                  */
                 if (!depth)
                         break;
                 /*
                  * Stop the search if we cross into another context:
                  */
                 if (curr->held_locks[depth].irq_context !=
                                 curr->held_locks[depth-1].irq_context)
                         break;
         }
         return 1;
 out_bug:
         if (!debug_locks_off_graph_unlock())
                 return 0;
 
         WARN_ON(1);
 
         return 0;
 }
 
 unsigned long nr_lock_chains;
 static struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
 
 /*
  * Look up a dependency chain. If the key is not present yet then
  * add it and return 1 - in this case the new dependency chain is
  * validated. If the key is already hashed, return 0.
  * (On return with 1 graph_lock is held.)
  */
 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;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return 0;
         /*
          * We can walk it lock-free, because entries only get added
          * to the hash:
          */
         list_for_each_entry(chain, hash_head, entry) {
                 if (chain->chain_key == chain_key) {
 cache_hit:
                         debug_atomic_inc(&chain_lookup_hits);
                         if (very_verbose(class))
                                 printk("\nhash chain already cached, key: "
                                         "%016Lx tail class: [%p] %s\n",
                                         (unsigned long long)chain_key,
                                         class->key, class->name);
                         return 0;
                 }
         }
         if (very_verbose(class))
                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
                         (unsigned long long)chain_key, class->key, class->name);
         /*
          * Allocate a new chain entry from the static array, and add
          * it to the hash:
          */
         if (!graph_lock())
                 return 0;
         /*
          * We have to walk the chain again locked - to avoid duplicates:
          */
         list_for_each_entry(chain, hash_head, entry) {
                 if (chain->chain_key == chain_key) {
                         graph_unlock();
                         goto cache_hit;
                 }
         }
         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
                 if (!debug_locks_off_graph_unlock())
                         return 0;
 
                 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
                 printk("turning off the locking correctness validator.\n");
                 return 0;
         }
         chain = lock_chains + nr_lock_chains++;
         chain->chain_key = chain_key;
         list_add_tail_rcu(&chain->entry, hash_head);
         debug_atomic_inc(&chain_lookup_misses);
         inc_chains();
 
         return 1;
 }
 
 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
                 struct held_lock *hlock, int chain_head, u64 chain_key)
 {
         /*
          * Trylock needs to maintain the stack of held locks, but it
          * does not add new dependencies, because trylock can be done
          * in any order.
          *
          * We look up the chain_key and do the O(N^2) check and update of
          * the dependencies only if this is a new dependency chain.
          * (If lookup_chain_cache() returns with 1 it acquires
          * graph_lock for us)
          */
         if (!hlock->trylock && (hlock->check == 2) &&
                         lookup_chain_cache(chain_key, hlock->class)) {
                 /*
                  * Check whether last held lock:
                  *
                  * - is irq-safe, if this lock is irq-unsafe
                  * - is softirq-safe, if this lock is hardirq-unsafe
                  *
                  * And check whether the new lock's dependency graph
                  * could lead back to the previous lock.
                  *
                  * any of these scenarios could lead to a deadlock. If
                  * All validations
                  */
                 int ret = check_deadlock(curr, hlock, lock, hlock->read);
 
                 if (!ret)
                         return 0;
                 /*
                  * Mark recursive read, as we jump over it when
                  * building dependencies (just like we jump over
                  * trylock entries):
                  */
                 if (ret == 2)
                         hlock->read = 2;
                 /*
                  * Add dependency only if this lock is not the head
                  * of the chain, and if it's not a secondary read-lock:
                  */
                 if (!chain_head && ret != 2)
                         if (!check_prevs_add(curr, hlock))
                                 return 0;
                 graph_unlock();
         } else
                 /* after lookup_chain_cache(): */
                 if (unlikely(!debug_locks))
                         return 0;
 
         return 1;
 }
 #else
 static inline int validate_chain(struct task_struct *curr,
                 struct lockdep_map *lock, struct held_lock *hlock,
                 int chain_head, u64 chain_key)
 {
         return 1;
 }
 #endif
 
 /*
  * We are building curr_chain_key incrementally, so double-check
  * it from scratch, to make sure that it's done correctly:
  */
 static void check_chain_key(struct task_struct *curr)
 {
 #ifdef CONFIG_DEBUG_LOCKDEP
         struct held_lock *hlock, *prev_hlock = NULL;
         unsigned int i, id;
         u64 chain_key = 0;
 
         for (i = 0; i < curr->lockdep_depth; i++) {
                 hlock = curr->held_locks + i;
                 if (chain_key != hlock->prev_chain_key) {
                         debug_locks_off();
                         printk("hm#1, depth: %u [%u], %016Lx != %016Lx\n",
                                 curr->lockdep_depth, i,
                                 (unsigned long long)chain_key,
                                 (unsigned long long)hlock->prev_chain_key);
                         WARN_ON(1);
                         return;
                 }
                 id = hlock->class - lock_classes;
                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
                         return;
 
                 if (prev_hlock && (prev_hlock->irq_context !=
                                                         hlock->irq_context))
                         chain_key = 0;
                 chain_key = iterate_chain_key(chain_key, id);
                 prev_hlock = hlock;
         }
         if (chain_key != curr->curr_chain_key) {
                 debug_locks_off();
                 printk("hm#2, depth: %u [%u], %016Lx != %016Lx\n",
                         curr->lockdep_depth, i,
                         (unsigned long long)chain_key,
                         (unsigned long long)curr->curr_chain_key);
                 WARN_ON(1);
         }
 #endif
 }
 
 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)
 {
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                 return 0;
 
         printk("\n=================================\n");
         printk(  "[ INFO: inconsistent lock state ]\n");
         print_kernel_version();
         printk(  "---------------------------------\n");
 
         printk("inconsistent {%s} -> {%s} usage.\n",
                 usage_str[prev_bit], usage_str[new_bit]);
 
         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
                 curr->comm, task_pid_nr(curr),
                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
                 trace_hardirqs_enabled(curr),
                 trace_softirqs_enabled(curr));
         print_lock(this);
 
         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
         print_stack_trace(this->class->usage_traces + prev_bit, 1);
 
         print_irqtrace_events(curr);
         printk("\nother info that might help us debug this:\n");
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 
 /*
  * Print out an error if an invalid bit is set:
  */
 static inline int
 valid_state(struct task_struct *curr, struct held_lock *this,
             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
 {
         if (unlikely(this->class->usage_mask & (1 << bad_bit)))
                 return print_usage_bug(curr, this, bad_bit, new_bit);
         return 1;
 }
 
 static int mark_lock(struct task_struct *curr, struct held_lock *this,
                      enum lock_usage_bit new_bit);
 
 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
 
 /*
  * print irq inversion bug:
  */
 static int
 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
                         struct held_lock *this, int forwards,
                         const char *irqclass)
 {
         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
                 return 0;
 
         printk("\n=========================================================\n");
         printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
         print_kernel_version();
         printk(  "---------------------------------------------------------\n");
         printk("%s/%d just changed the state of lock:\n",
                 curr->comm, task_pid_nr(curr));
         print_lock(this);
         if (forwards)
                 printk("but this lock took another, %s-irq-unsafe lock in the past:\n", irqclass);
         else
                 printk("but this lock was taken by another, %s-irq-safe lock in the past:\n", irqclass);
         print_lock_name(other);
         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
 
         printk("\nother info that might help us debug this:\n");
         lockdep_print_held_locks(curr);
 
         printk("\nthe first lock's dependencies:\n");
         print_lock_dependencies(this->class, 0);
 
         printk("\nthe second lock's dependencies:\n");
         print_lock_dependencies(other, 0);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 
 /*
  * Prove that in the forwards-direction subgraph starting at <this>
  * there is no lock matching <mask>:
  */
 static int
 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
                      enum lock_usage_bit bit, const char *irqclass)
 {
         int ret;
 
         find_usage_bit = bit;
         /* fills in <forwards_match> */
         ret = find_usage_forwards(this->class, 0);
         if (!ret || ret == 1)
                 return ret;
 
         return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
 }
 
 /*
  * Prove that in the backwards-direction subgraph starting at <this>
  * there is no lock matching <mask>:
  */
 static int
 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
                       enum lock_usage_bit bit, const char *irqclass)
 {
         int ret;
 
         find_usage_bit = bit;
         /* fills in <backwards_match> */
         ret = find_usage_backwards(this->class, 0);
         if (!ret || ret == 1)
                 return ret;
 
         return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
 }
 
 void print_irqtrace_events(struct task_struct *curr)
 {
         printk("irq event stamp: %u\n", curr->irq_events);
         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
         print_ip_sym(curr->hardirq_enable_ip);
         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
         print_ip_sym(curr->hardirq_disable_ip);
         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
         print_ip_sym(curr->softirq_enable_ip);
         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
         print_ip_sym(curr->softirq_disable_ip);
 }
 
 static int hardirq_verbose(struct lock_class *class)
 {
 #if HARDIRQ_VERBOSE
         return class_filter(class);
 #endif
         return 0;
 }
 
 static int softirq_verbose(struct lock_class *class)
 {
 #if SOFTIRQ_VERBOSE
         return class_filter(class);
 #endif
         return 0;
 }
 
 #define STRICT_READ_CHECKS      1
 
 static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                 enum lock_usage_bit new_bit)
 {
         int ret = 1;
 
         switch(new_bit) {
         case LOCK_USED_IN_HARDIRQ:
                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
                         return 0;
                 if (!valid_state(curr, this, new_bit,
                                  LOCK_ENABLED_HARDIRQS_READ))
                         return 0;
                 /*
                  * just marked it hardirq-safe, check that this lock
                  * took no hardirq-unsafe lock in the past:
                  */
                 if (!check_usage_forwards(curr, this,
                                           LOCK_ENABLED_HARDIRQS, "hard"))
                         return 0;
 #if STRICT_READ_CHECKS
                 /*
                  * just marked it hardirq-safe, check that this lock
                  * took no hardirq-unsafe-read lock in the past:
                  */
                 if (!check_usage_forwards(curr, this,
                                 LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
                         return 0;
 #endif
                 if (hardirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_USED_IN_SOFTIRQ:
                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
                         return 0;
                 if (!valid_state(curr, this, new_bit,
                                  LOCK_ENABLED_SOFTIRQS_READ))
                         return 0;
                 /*
                  * just marked it softirq-safe, check that this lock
                  * took no softirq-unsafe lock in the past:
                  */
                 if (!check_usage_forwards(curr, this,
                                           LOCK_ENABLED_SOFTIRQS, "soft"))
                         return 0;
 #if STRICT_READ_CHECKS
                 /*
                  * just marked it softirq-safe, check that this lock
                  * took no softirq-unsafe-read lock in the past:
                  */
                 if (!check_usage_forwards(curr, this,
                                 LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
                         return 0;
 #endif
                 if (softirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_USED_IN_HARDIRQ_READ:
                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
                         return 0;
                 /*
                  * just marked it hardirq-read-safe, check that this lock
                  * took no hardirq-unsafe lock in the past:
                  */
                 if (!check_usage_forwards(curr, this,
                                           LOCK_ENABLED_HARDIRQS, "hard"))
                         return 0;
                 if (hardirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_USED_IN_SOFTIRQ_READ:
                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
                         return 0;
                 /*
                  * just marked it softirq-read-safe, check that this lock
                  * took no softirq-unsafe lock in the past:
                  */
                 if (!check_usage_forwards(curr, this,
                                           LOCK_ENABLED_SOFTIRQS, "soft"))
                         return 0;
                 if (softirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_ENABLED_HARDIRQS:
                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
                         return 0;
                 if (!valid_state(curr, this, new_bit,
                                  LOCK_USED_IN_HARDIRQ_READ))
                         return 0;
                 /*
                  * just marked it hardirq-unsafe, check that no hardirq-safe
                  * lock in the system ever took it in the past:
                  */
                 if (!check_usage_backwards(curr, this,
                                            LOCK_USED_IN_HARDIRQ, "hard"))
                         return 0;
 #if STRICT_READ_CHECKS
                 /*
                  * just marked it hardirq-unsafe, check that no
                  * hardirq-safe-read lock in the system ever took
                  * it in the past:
                  */
                 if (!check_usage_backwards(curr, this,
                                    LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
                         return 0;
 #endif
                 if (hardirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_ENABLED_SOFTIRQS:
                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
                         return 0;
                 if (!valid_state(curr, this, new_bit,
                                  LOCK_USED_IN_SOFTIRQ_READ))
                         return 0;
                 /*
                  * just marked it softirq-unsafe, check that no softirq-safe
                  * lock in the system ever took it in the past:
                  */
                 if (!check_usage_backwards(curr, this,
                                            LOCK_USED_IN_SOFTIRQ, "soft"))
                         return 0;
 #if STRICT_READ_CHECKS
                 /*
                  * just marked it softirq-unsafe, check that no
                  * softirq-safe-read lock in the system ever took
                  * it in the past:
                  */
                 if (!check_usage_backwards(curr, this,
                                    LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
                         return 0;
 #endif
                 if (softirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_ENABLED_HARDIRQS_READ:
                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
                         return 0;
 #if STRICT_READ_CHECKS
                 /*
                  * just marked it hardirq-read-unsafe, check that no
                  * hardirq-safe lock in the system ever took it in the past:
                  */
                 if (!check_usage_backwards(curr, this,
                                            LOCK_USED_IN_HARDIRQ, "hard"))
                         return 0;
 #endif
                 if (hardirq_verbose(this->class))
                         ret = 2;
                 break;
         case LOCK_ENABLED_SOFTIRQS_READ:
                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
                         return 0;
 #if STRICT_READ_CHECKS
                 /*
                  * just marked it softirq-read-unsafe, check that no
                  * softirq-safe lock in the system ever took it in the past:
                  */
                 if (!check_usage_backwards(curr, this,
                                            LOCK_USED_IN_SOFTIRQ, "soft"))
                         return 0;
 #endif
                 if (softirq_verbose(this->class))
                         ret = 2;
                 break;
         default:
                 WARN_ON(1);
                 break;
         }
 
         return ret;
 }
 
 /*
  * Mark all held locks with a usage bit:
  */
 static int
 mark_held_locks(struct task_struct *curr, int hardirq)
 {
         enum lock_usage_bit usage_bit;
         struct held_lock *hlock;
         int i;
 
         for (i = 0; i < curr->lockdep_depth; i++) {
                 hlock = curr->held_locks + i;
 
                 if (hardirq) {
                         if (hlock->read)
                                 usage_bit = LOCK_ENABLED_HARDIRQS_READ;
                         else
                                 usage_bit = LOCK_ENABLED_HARDIRQS;
                 } else {
                         if (hlock->read)
                                 usage_bit = LOCK_ENABLED_SOFTIRQS_READ;
                         else
                                 usage_bit = LOCK_ENABLED_SOFTIRQS;
                 }
                 if (!mark_lock(curr, hlock, usage_bit))
                         return 0;
         }
 
         return 1;
 }
 
 /*
  * 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 a0)
 {
         struct task_struct *curr = current;
         unsigned long ip;
 
         time_hardirqs_on(CALLER_ADDR0, a0);
         if (unlikely(!debug_locks || current->lockdep_recursion))
                 return;
 
         if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
                 return;
 
         if (unlikely(curr->hardirqs_enabled)) {
                 debug_atomic_inc(&redundant_hardirqs_on);
                 return;
         }
         /* we'll do an OFF -> ON transition: */
         curr->hardirqs_enabled = 1;
         ip = (unsigned long) __builtin_return_address(0);
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return;
         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
                 return;
         /*
          * We are going to turn hardirqs on, so set the
          * usage bit for all held locks:
          */
         if (!mark_held_locks(curr, 1))
                 return;
         /*
          * If we have softirqs enabled, then set the usage
          * bit for all held locks. (disabled hardirqs prevented
          * this bit from being set before)
          */
         if (curr->softirqs_enabled)
                 if (!mark_held_locks(curr, 0))
                         return;
 
         curr->hardirq_enable_ip = ip;
         curr->hardirq_enable_event = ++curr->irq_events;
         debug_atomic_inc(&hardirqs_on_events);
 }
 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
 void trace_hardirqs_on(void)
 {
         trace_hardirqs_on_caller(CALLER_ADDR0);
 }
 EXPORT_SYMBOL(trace_hardirqs_on);
 
 /*
  * Hardirqs were disabled:
  */
 void trace_hardirqs_off_caller(unsigned long a0)
 {
         struct task_struct *curr = current;
 
         time_hardirqs_off(CALLER_ADDR0, a0);
 
         if (unlikely(!debug_locks || current->lockdep_recursion))
                 return;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return;
 
         if (curr->hardirqs_enabled) {
                 /*
                  * We have done an ON -> OFF transition:
                  */
                 curr->hardirqs_enabled = 0;
                 curr->hardirq_disable_ip = _RET_IP_;
                 curr->hardirq_disable_event = ++curr->irq_events;
                 debug_atomic_inc(&hardirqs_off_events);
         } else
                 debug_atomic_inc(&redundant_hardirqs_off);
 }
 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 
 void trace_hardirqs_off(void)
 {
         trace_hardirqs_off_caller(CALLER_ADDR0);
 }
 EXPORT_SYMBOL(trace_hardirqs_off);
 
 /*
  * Softirqs will be enabled:
  */
 void trace_softirqs_on(unsigned long ip)
 {
         struct task_struct *curr = current;
 
         if (unlikely(!debug_locks))
                 return;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return;
 
         if (curr->softirqs_enabled) {
                 debug_atomic_inc(&redundant_softirqs_on);
                 return;
         }
 
         /*
          * We'll do an OFF -> ON transition:
          */
         curr->softirqs_enabled = 1;
         curr->softirq_enable_ip = ip;
         curr->softirq_enable_event = ++curr->irq_events;
         debug_atomic_inc(&softirqs_on_events);
         /*
          * We are going to turn softirqs on, so set the
          * usage bit for all held locks, if hardirqs are
          * enabled too:
          */
         if (curr->hardirqs_enabled)
                 mark_held_locks(curr, 0);
 }
 
 /*
  * Softirqs were disabled:
  */
 void trace_softirqs_off(unsigned long ip)
 {
         struct task_struct *curr = current;
 
         if (unlikely(!debug_locks))
                 return;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return;
 
         if (curr->softirqs_enabled) {
                 /*
                  * We have done an ON -> OFF transition:
                  */
                 curr->softirqs_enabled = 0;
                 curr->softirq_disable_ip = ip;
                 curr->softirq_disable_event = ++curr->irq_events;
                 debug_atomic_inc(&softirqs_off_events);
                 DEBUG_LOCKS_WARN_ON(!softirq_count());
         } else
                 debug_atomic_inc(&redundant_softirqs_off);
 }
 
 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
 {
         /*
          * If non-trylock use in a hardirq or softirq context, then
          * mark the lock as used in these contexts:
          */
         if (!hlock->trylock) {
                 if (hlock->read) {
                         if (curr->hardirq_context)
                                 if (!mark_lock(curr, hlock,
                                                 LOCK_USED_IN_HARDIRQ_READ))
                                         return 0;
                         if (curr->softirq_context)
                                 if (!mark_lock(curr, hlock,
                                                 LOCK_USED_IN_SOFTIRQ_READ))
                                         return 0;
                 } else {
                         if (curr->hardirq_context)
                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
                                         return 0;
                         if (curr->softirq_context)
                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
                                         return 0;
                 }
         }
         if (!hlock->hardirqs_off) {
                 if (hlock->read) {
                         if (!mark_lock(curr, hlock,
                                         LOCK_ENABLED_HARDIRQS_READ))
                                 return 0;
                         if (curr->softirqs_enabled)
                                 if (!mark_lock(curr, hlock,
                                                 LOCK_ENABLED_SOFTIRQS_READ))
                                         return 0;
                 } else {
                         if (!mark_lock(curr, hlock,
                                         LOCK_ENABLED_HARDIRQS))
                                 return 0;
                         if (curr->softirqs_enabled)
                                 if (!mark_lock(curr, hlock,
                                                 LOCK_ENABLED_SOFTIRQS))
                                         return 0;
                 }
         }
 
         return 1;
 }
 
 static int separate_irq_context(struct task_struct *curr,
                 struct held_lock *hlock)
 {
         unsigned int depth = curr->lockdep_depth;
 
         /*
          * Keep track of points where we cross into an interrupt context:
          */
         hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
                                 curr->softirq_context;
         if (depth) {
                 struct held_lock *prev_hlock;
 
                 prev_hlock = curr->held_locks + depth-1;
                 /*
                  * If we cross into another context, reset the
                  * hash key (this also prevents the checking and the
                  * adding of the dependency to 'prev'):
                  */
                 if (prev_hlock->irq_context != hlock->irq_context)
                         return 1;
         }
         return 0;
 }
 
 #else
 
 static inline
 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                 enum lock_usage_bit new_bit)
 {
         WARN_ON(1);
         return 1;
 }
 
 static inline int mark_irqflags(struct task_struct *curr,
                 struct held_lock *hlock)
 {
         return 1;
 }
 
 static inline int separate_irq_context(struct task_struct *curr,
                 struct held_lock *hlock)
 {
         return 0;
 }
 
 #endif
 
 /*
  * Mark a lock with a usage bit, and validate the state transition:
  */
 static int mark_lock(struct task_struct *curr, struct held_lock *this,
                      enum lock_usage_bit new_bit)
 {
         unsigned int new_mask = 1 << new_bit, ret = 1;
 
         /*
          * If already set then do not dirty the cacheline,
          * nor do any checks:
          */
         if (likely(this->class->usage_mask & new_mask))
                 return 1;
 
         if (!graph_lock())
                 return 0;
         /*
          * Make sure we didnt race:
          */
         if (unlikely(this->class->usage_mask & new_mask)) {
                 graph_unlock();
                 return 1;
         }
 
         this->class->usage_mask |= new_mask;
 
         if (!save_trace(this->class->usage_traces + new_bit))
                 return 0;
 
         switch (new_bit) {
         case LOCK_USED_IN_HARDIRQ:
         case LOCK_USED_IN_SOFTIRQ:
         case LOCK_USED_IN_HARDIRQ_READ:
         case LOCK_USED_IN_SOFTIRQ_READ:
         case LOCK_ENABLED_HARDIRQS:
         case LOCK_ENABLED_SOFTIRQS:
         case LOCK_ENABLED_HARDIRQS_READ:
         case LOCK_ENABLED_SOFTIRQS_READ:
                 ret = mark_lock_irq(curr, this, new_bit);
                 if (!ret)
                         return 0;
                 break;
         case LOCK_USED:
                 debug_atomic_dec(&nr_unused_locks);
                 break;
         default:
                 if (!debug_locks_off_graph_unlock())
                         return 0;
                 WARN_ON(1);
                 return 0;
         }
 
         graph_unlock();
 
         /*
          * We must printk outside of the graph_lock:
          */
         if (ret == 2) {
                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
                 print_lock(this);
                 print_irqtrace_events(curr);
                 dump_stack();
         }
 
         return ret;
 }
 
 /*
  * Initialize a lock instance's lock-class mapping info:
  */
 void lockdep_init_map(struct lockdep_map *lock, const char *name,
                       struct lock_class_key *key, int subclass)
 {
         if (unlikely(!debug_locks))
                 return;
 
         if (DEBUG_LOCKS_WARN_ON(!key))
                 return;
         if (DEBUG_LOCKS_WARN_ON(!name))
                 return;
         /*
          * Sanity check, the lock-class key must be persistent:
          */
         if (!static_obj(key)) {
                 printk("BUG: key %p not in .data!\n", key);
                 DEBUG_LOCKS_WARN_ON(1);
                 return;
         }
         lock->name = name;
         lock->key = key;
         lock->class_cache = NULL;
 #ifdef CONFIG_LOCK_STAT
         lock->cpu = raw_smp_processor_id();
 #endif
         if (subclass)
                 register_lock_class(lock, subclass, 1);
 }
 
 EXPORT_SYMBOL_GPL(lockdep_init_map);
 
 /*
  * This gets called for every mutex_lock*()/spin_lock*() operation.
  * We maintain the dependency maps and validate the locking attempt:
  */
 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                           int trylock, int read, int check, int hardirqs_off,
                           unsigned long ip)
 {
         struct task_struct *curr = current;
         struct lock_class *class = NULL;
         struct held_lock *hlock;
         unsigned int depth, id;
         int chain_head = 0;
         u64 chain_key;
 
         if (!prove_locking)
                 check = 1;
 
         if (unlikely(!debug_locks))
                 return 0;
 
         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");
                 return 0;
         }
 
         if (!subclass)
                 class = lock->class_cache;
         /*
          * Not cached yet or subclass?
          */
         if (unlikely(!class)) {
                 class = register_lock_class(lock, subclass, 0);
                 if (!class)
                         return 0;
         }
         debug_atomic_inc((atomic_t *)&class->ops);
         if (very_verbose(class)) {
                 printk("\nacquire class [%p] %s", class->key, class->name);
                 if (class->name_version > 1)
                         printk("#%d", class->name_version);
                 printk("\n");
                 dump_stack();
         }
 
         /*
          * Add the lock to the list of currently held locks.
          * (we dont increase the depth just yet, up until the
          * dependency checks are done)
          */
         depth = curr->lockdep_depth;
         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
                 return 0;
 
         hlock = curr->held_locks + depth;
 
         hlock->class = class;
         hlock->acquire_ip = ip;
         hlock->instance = lock;
         hlock->trylock = trylock;
         hlock->read = read;
         hlock->check = check;
         hlock->hardirqs_off = hardirqs_off;
 #ifdef CONFIG_LOCK_STAT
         hlock->waittime_stamp = 0;
         hlock->holdtime_stamp = sched_clock();
 #endif
 
         if (check == 2 && !mark_irqflags(curr, hlock))
                 return 0;
 
         /* mark it as used: */
         if (!mark_lock(curr, hlock, LOCK_USED))
                 return 0;
 
         /*
          * Calculate the chain hash: it's the combined hash of all the
          * lock keys along the dependency chain. We save the hash value
          * at every step so that we can get the current hash easily
          * after unlock. The chain hash is then used to cache dependency
          * results.
          *
          * The 'key ID' is what is the most compact key value to drive
          * the hash, not class->key.
          */
         id = class - lock_classes;
         if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
                 return 0;
 
         chain_key = curr->curr_chain_key;
         if (!depth) {
                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
                         return 0;
                 chain_head = 1;
         }
 
         hlock->prev_chain_key = chain_key;
         if (separate_irq_context(curr, hlock)) {
                 chain_key = 0;
                 chain_head = 1;
         }
         chain_key = iterate_chain_key(chain_key, id);
 
         if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
                 return 0;
 
         curr->curr_chain_key = chain_key;
         curr->lockdep_depth++;
         check_chain_key(curr);
 #ifdef CONFIG_DEBUG_LOCKDEP
         if (unlikely(!debug_locks))
                 return 0;
 #endif
         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
                 debug_locks_off();
                 printk("BUG: MAX_LOCK_DEPTH too low!\n");
                 printk("turning off the locking correctness validator.\n");
                 return 0;
         }
 
         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
                 max_lockdep_depth = curr->lockdep_depth;
 
         return 1;
 }
 
 static int
 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
                            unsigned long ip)
 {
         if (!debug_locks_off())
                 return 0;
         if (debug_locks_silent)
                 return 0;
 
         printk("\n=====================================\n");
         printk(  "[ BUG: bad unlock balance detected! ]\n");
         printk(  "-------------------------------------\n");
         printk("%s/%d is trying to release lock (",
                 curr->comm, task_pid_nr(curr));
         print_lockdep_cache(lock);
         printk(") at:\n");
         print_ip_sym(ip);
         printk("but there are no more locks to release!\n");
         printk("\nother info that might help us debug this:\n");
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 
 /*
  * Common debugging checks for both nested and non-nested unlock:
  */
 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
                         unsigned long ip)
 {
         if (unlikely(!debug_locks))
                 return 0;
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return 0;
 
         if (curr->lockdep_depth <= 0)
                 return print_unlock_inbalance_bug(curr, lock, ip);
 
         return 1;
 }
 
 static int
 __lock_set_subclass(struct lockdep_map *lock,
                     unsigned int subclass, unsigned long ip)
 {
         struct task_struct *curr = current;
         struct held_lock *hlock, *prev_hlock;
         struct lock_class *class;
         unsigned int depth;
         int i;
 
         depth = curr->lockdep_depth;
         if (DEBUG_LOCKS_WARN_ON(!depth))
                 return 0;
 
         prev_hlock = NULL;
         for (i = depth-1; i >= 0; i--) {
                 hlock = curr->held_locks + i;
                 /*
                  * We must not cross into another context:
                  */
                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                         break;
                 if (hlock->instance == lock)
                         goto found_it;
                 prev_hlock = hlock;
         }
         return print_unlock_inbalance_bug(curr, lock, ip);
 
 found_it:
         class = register_lock_class(lock, subclass, 0);
         hlock->class = class;
 
         curr->lockdep_depth = i;
         curr->curr_chain_key = hlock->prev_chain_key;
 
         for (; i < depth; i++) {
                 hlock = curr->held_locks + i;
                 if (!__lock_acquire(hlock->instance,
                         hlock->class->subclass, hlock->trylock,
                                 hlock->read, hlock->check, hlock->hardirqs_off,
                                 hlock->acquire_ip))
                         return 0;
         }
 
         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
                 return 0;
         return 1;
 }
 
 /*
  * Remove the lock to the list of currently held locks in a
  * potentially non-nested (out of order) manner. This is a
  * relatively rare operation, as all the unlock APIs default
  * to nested mode (which uses lock_release()):
  */
 static int
 lock_release_non_nested(struct task_struct *curr,
                         struct lockdep_map *lock, unsigned long ip)
 {
         struct held_lock *hlock, *prev_hlock;
         unsigned int depth;
         int i;
 
         /*
          * Check whether the lock exists in the current stack
          * of held locks:
          */
         depth = curr->lockdep_depth;
         if (DEBUG_LOCKS_WARN_ON(!depth))
                 return 0;
 
         prev_hlock = NULL;
         for (i = depth-1; i >= 0; i--) {
                 hlock = curr->held_locks + i;
                 /*
                  * We must not cross into another context:
                  */
                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                         break;
                 if (hlock->instance == lock)
                         goto found_it;
                 prev_hlock = hlock;
         }
         return print_unlock_inbalance_bug(curr, lock, ip);
 
 found_it:
         lock_release_holdtime(hlock);
 
         /*
          * We have the right lock to unlock, 'hlock' points to it.
          * Now we remove it from the stack, and add back the other
          * entries (if any), recalculating the hash along the way:
          */
         curr->lockdep_depth = i;
         curr->curr_chain_key = hlock->prev_chain_key;
 
         for (i++; i < depth; i++) {
                 hlock = curr->held_locks + i;
                 if (!__lock_acquire(hlock->instance,
                         hlock->class->subclass, hlock->trylock,
                                 hlock->read, hlock->check, hlock->hardirqs_off,
                                 hlock->acquire_ip))
                         return 0;
         }
 
         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
                 return 0;
         return 1;
 }
 
 /*
  * Remove the lock to the list of currently held locks - this gets
  * called on mutex_unlock()/spin_unlock*() (or on a failed
  * mutex_lock_interruptible()). This is done for unlocks that nest
  * perfectly. (i.e. the current top of the lock-stack is unlocked)
  */
 static int lock_release_nested(struct task_struct *curr,
                                struct lockdep_map *lock, unsigned long ip)
 {
         struct held_lock *hlock;
         unsigned int depth;
 
         /*
          * Pop off the top of the lock stack:
          */
         depth = curr->lockdep_depth - 1;
         hlock = curr->held_locks + depth;
 
         /*
          * Is the unlock non-nested:
          */
         if (hlock->instance != lock)
                 return lock_release_non_nested(curr, lock, ip);
         curr->lockdep_depth--;
 
         if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
                 return 0;
 
         curr->curr_chain_key = hlock->prev_chain_key;
 
         lock_release_holdtime(hlock);
 
 #ifdef CONFIG_DEBUG_LOCKDEP
         hlock->prev_chain_key = 0;
         hlock->class = NULL;
         hlock->acquire_ip = 0;
         hlock->irq_context = 0;
 #endif
         return 1;
 }
 
 /*
  * Remove the lock to the list of currently held locks - this gets
  * called on mutex_unlock()/spin_unlock*() (or on a failed
  * mutex_lock_interruptible()). This is done for unlocks that nest
  * perfectly. (i.e. the current top of the lock-stack is unlocked)
  */
 static void
 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
 {
         struct task_struct *curr = current;
 
         if (!check_unlock(curr, lock, ip))
                 return;
 
         if (nested) {
                 if (!lock_release_nested(curr, lock, ip))
                         return;
         } else {
                 if (!lock_release_non_nested(curr, lock, ip))
                         return;
         }
 
         check_chain_key(curr);
 }
 
 /*
  * Check whether we follow the irq-flags state precisely:
  */
 static void check_flags(unsigned long flags)
 {
 #if defined(CONFIG_DEBUG_LOCKDEP) && defined(CONFIG_TRACE_IRQFLAGS)
         if (!debug_locks)
                 return;
 
         if (irqs_disabled_flags(flags)) {
                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
                         printk("possible reason: unannotated irqs-off.\n");
                 }
         } else {
                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
                         printk("possible reason: unannotated irqs-on.\n");
                 }
         }
 
         /*
          * We dont accurately track softirq state in e.g.
          * hardirq contexts (such as on 4KSTACKS), so only
          * check if not in hardirq contexts:
          */
         if (!hardirq_count()) {
                 if (softirq_count())
                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
                 else
                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
         }
 
         if (!debug_locks)
                 print_irqtrace_events(current);
 #endif
 }
 
 void
 lock_set_subclass(struct lockdep_map *lock,
                   unsigned int subclass, unsigned long ip)
 {
         unsigned long flags;
 
         if (unlikely(!lock_stat && !prove_locking))
                 return;
 
         if (unlikely(current->lockdep_recursion))
                 return;
 
         raw_local_irq_save(flags);
         current->lockdep_recursion = 1;
         check_flags(flags);
         if (__lock_set_subclass(lock, subclass, ip))
                 check_chain_key(current);
         current->lockdep_recursion = 0;
         raw_local_irq_restore(flags);
 }
 
 EXPORT_SYMBOL_GPL(lock_set_subclass);
 
 /*
  * We are not always called with irqs disabled - do that here,
  * and also avoid lockdep recursion:
  */
 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                   int trylock, int read, int check, unsigned long ip)
 {
         unsigned long flags;
 
         if (unlikely(!lock_stat && !prove_locking))
                 return;
 
         if (unlikely(current->lockdep_recursion))
                 return;
 
         raw_local_irq_save(flags);
         check_flags(flags);
 
         current->lockdep_recursion = 1;
         __lock_acquire(lock, subclass, trylock, read, check,
                        irqs_disabled_flags(flags), ip);
         current->lockdep_recursion = 0;
         raw_local_irq_restore(flags);
 }
 
 EXPORT_SYMBOL_GPL(lock_acquire);
 
 void lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
 {
         unsigned long flags;
 
         if (unlikely(!lock_stat && !prove_locking))
                 return;
 
         if (unlikely(current->lockdep_recursion))
                 return;
 
         raw_local_irq_save(flags);
         check_flags(flags);
         current->lockdep_recursion = 1;
         __lock_release(lock, nested, ip);
         current->lockdep_recursion = 0;
         raw_local_irq_restore(flags);
 }
 
 EXPORT_SYMBOL_GPL(lock_release);
 
 #ifdef CONFIG_LOCK_STAT
 static int
 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
                            unsigned long ip)
 {
         if (!debug_locks_off())
                 return 0;
         if (debug_locks_silent)
                 return 0;
 
         printk("\n=================================\n");
         printk(  "[ BUG: bad contention detected! ]\n");
         printk(  "---------------------------------\n");
         printk("%s/%d is trying to contend lock (",
                 curr->comm, task_pid_nr(curr));
         print_lockdep_cache(lock);
         printk(") at:\n");
         print_ip_sym(ip);
         printk("but there are no locks held!\n");
         printk("\nother info that might help us debug this:\n");
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 
         return 0;
 }
 
 static void
 __lock_contended(struct lockdep_map *lock, unsigned long ip)
 {
         struct task_struct *curr = current;
         struct held_lock *hlock, *prev_hlock;
         struct lock_class_stats *stats;
         unsigned int depth;
         int i, point;
 
         depth = curr->lockdep_depth;
         if (DEBUG_LOCKS_WARN_ON(!depth))
                 return;
 
         prev_hlock = NULL;
         for (i = depth-1; i >= 0; i--) {
                 hlock = curr->held_locks + i;
                 /*
                  * We must not cross into another context:
                  */
                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                         break;
                 if (hlock->instance == lock)
                         goto found_it;
                 prev_hlock = hlock;
         }
         print_lock_contention_bug(curr, lock, ip);
         return;
 
 found_it:
         hlock->waittime_stamp = sched_clock();
 
         point = lock_contention_point(hlock->class, ip);
 
         stats = get_lock_stats(hlock->class);
         if (point < ARRAY_SIZE(stats->contention_point))
                 stats->contention_point[point]++;
         if (lock->cpu != smp_processor_id())
                 stats->bounces[bounce_contended + !!hlock->read]++;
         put_lock_stats(stats);
 }
 
 static void
 __lock_acquired(struct lockdep_map *lock)
 {
         struct task_struct *curr = current;
         struct held_lock *hlock, *prev_hlock;
         struct lock_class_stats *stats;
         unsigned int depth;
         u64 now;
         s64 waittime = 0;
         int i, cpu;
 
         depth = curr->lockdep_depth;
         if (DEBUG_LOCKS_WARN_ON(!depth))
                 return;
 
         prev_hlock = NULL;
         for (i = depth-1; i >= 0; i--) {
                 hlock = curr->held_locks + i;
                 /*
                  * We must not cross into another context:
                  */
                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
                         break;
                 if (hlock->instance == lock)
                         goto found_it;
                 prev_hlock = hlock;
         }
         print_lock_contention_bug(curr, lock, _RET_IP_);
         return;
 
 found_it:
         cpu = smp_processor_id();
         if (hlock->waittime_stamp) {
                 now = sched_clock();
                 waittime = now - hlock->waittime_stamp;
                 hlock->holdtime_stamp = now;
         }
 
         stats = get_lock_stats(hlock->class);
         if (waittime) {
                 if (hlock->read)
                         lock_time_inc(&stats->read_waittime, waittime);
                 else
                         lock_time_inc(&stats->write_waittime, waittime);
         }
         if (lock->cpu != cpu)
                 stats->bounces[bounce_acquired + !!hlock->read]++;
         put_lock_stats(stats);
 
         lock->cpu = cpu;
 }
 
 void lock_contended(struct lockdep_map *lock, unsigned long ip)
 {
         unsigned long flags;
 
         if (unlikely(!lock_stat))
                 return;
 
         if (unlikely(current->lockdep_recursion))
                 return;
 
         raw_local_irq_save(flags);
         check_flags(flags);
         current->lockdep_recursion = 1;
         __lock_contended(lock, ip);
         current->lockdep_recursion = 0;
         raw_local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(lock_contended);
 
 void lock_acquired(struct lockdep_map *lock)
 {
         unsigned long flags;
 
         if (unlikely(!lock_stat))
                 return;
 
         if (unlikely(current->lockdep_recursion))
                 return;
 
         raw_local_irq_save(flags);
         check_flags(flags);
         current->lockdep_recursion = 1;
         __lock_acquired(lock);
         current->lockdep_recursion = 0;
         raw_local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(lock_acquired);
 #endif
 
 /*
  * Used by the testsuite, sanitize the validator state
  * after a simulated failure:
  */
 
 void lockdep_reset(void)
 {
         unsigned long flags;
         int i;
 
         raw_local_irq_save(flags);
         current->curr_chain_key = 0;
         current->lockdep_depth = 0;
         current->lockdep_recursion = 0;
         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
         nr_hardirq_chains = 0;
         nr_softirq_chains = 0;
         nr_process_chains = 0;
         debug_locks = 1;
         for (i = 0; i < CHAINHASH_SIZE; i++)
                 INIT_LIST_HEAD(chainhash_table + i);
         raw_local_irq_restore(flags);
 }
 
 static void zap_class(struct lock_class *class)
 {
         int i;
 
         /*
          * Remove all dependencies this lock is
          * involved in:
          */
         for (i = 0; i < nr_list_entries; i++) {
                 if (list_entries[i].class == class)
                         list_del_rcu(&list_entries[i].entry);
         }
         /*
          * Unhash the class and remove it from the all_lock_classes list:
          */
         list_del_rcu(&class->hash_entry);
         list_del_rcu(&class->lock_entry);
 
 }
 
 static inline int within(const void *addr, void *start, unsigned long size)
 {
         return addr >= start && addr < start + size;
 }
 
 void lockdep_free_key_range(void *start, unsigned long size)
 {
         struct lock_class *class, *next;
         struct list_head *head;
         unsigned long flags;
         int i;
         int locked;
 
         raw_local_irq_save(flags);
         locked = graph_lock();
 
         /*
          * Unhash all classes that were created by this module:
          */
         for (i = 0; i < CLASSHASH_SIZE; i++) {
                 head = classhash_table + i;
                 if (list_empty(head))
                         continue;
                 list_for_each_entry_safe(class, next, head, hash_entry) {
                         if (within(class->key, start, size))
                                 zap_class(class);
                         else if (within(class->name, start, size))
                                 zap_class(class);
                 }
         }
 
         if (locked)
                 graph_unlock();
         raw_local_irq_restore(flags);
 }
 
 void lockdep_reset_lock(struct lockdep_map *lock)
 {
         struct lock_class *class, *next;
         struct list_head *head;
         unsigned long flags;
         int i, j;
         int locked;
 
         raw_local_irq_save(flags);
 
         /*
          * Remove all classes this lock might have:
          */
         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
                 /*
                  * If the class exists we look it up and zap it:
                  */
                 class = look_up_lock_class(lock, j);
                 if (class)
                         zap_class(class);
         }
         /*
          * Debug check: in the end all mapped classes should
          * be gone.
          */
         locked = graph_lock();
         for (i = 0; i < CLASSHASH_SIZE; i++) {
                 head = classhash_table + i;
                 if (list_empty(head))
                         continue;
                 list_for_each_entry_safe(class, next, head, hash_entry) {
                         if (unlikely(class == lock->class_cache)) {
                                 if (debug_locks_off_graph_unlock())
                                         WARN_ON(1);
                                 goto out_restore;
                         }
                 }
         }
         if (locked)
                 graph_unlock();
 
 out_restore:
         raw_local_irq_restore(flags);
 }
 
 void lockdep_init(void)
 {
         int i;
 
         /*
          * Some architectures have their own start_kernel()
          * code which calls lockdep_init(), while we also
          * call lockdep_init() from the start_kernel() itself,
          * and we want to initialize the hashes only once:
          */
         if (lockdep_initialized)
                 return;
 
         for (i = 0; i < CLASSHASH_SIZE; i++)
                 INIT_LIST_HEAD(classhash_table + i);
 
         for (i = 0; i < CHAINHASH_SIZE; i++)
                 INIT_LIST_HEAD(chainhash_table + i);
 
         lockdep_initialized = 1;
 }
 
 void __init lockdep_info(void)
 {
         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
 
         printk("... MAX_LOCKDEP_SUBCLASSES: %6lu\n", MAX_LOCKDEP_SUBCLASSES);
         printk("... MAX_LOCK_DEPTH:         %6lu\n", MAX_LOCK_DEPTH);
         printk("... MAX_LOCKDEP_KEYS:       %6lu\n", MAX_LOCKDEP_KEYS);
         printk("... CLASSHASH_SIZE:         %6lu\n", CLASSHASH_SIZE);
         printk("... MAX_LOCKDEP_ENTRIES:    %6lu\n", MAX_LOCKDEP_ENTRIES);
         printk("... MAX_LOCKDEP_CHAINS:     %6lu\n", MAX_LOCKDEP_CHAINS);
         printk("... CHAINHASH_SIZE:         %6lu\n", CHAINHASH_SIZE);
 
         printk(" memory used by lock dependency info: %lu kB\n",
                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
                 sizeof(struct list_head) * CLASSHASH_SIZE +
                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
                 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
 
         printk(" per task-struct memory footprint: %lu bytes\n",
                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
 
 #ifdef CONFIG_DEBUG_LOCKDEP
         if (lockdep_init_error) {
                 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
                 printk("Call stack leading to lockdep invocation was:\n");
                 print_stack_trace(&lockdep_init_trace, 0);
         }
 #endif
 }
 
 static void
 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
                      const void *mem_to, struct held_lock *hlock)
 {
         if (!debug_locks_off())
                 return;
         if (debug_locks_silent)
                 return;
 
         printk("\n=========================\n");
         printk(  "[ BUG: held lock freed! ]\n");
         printk(  "-------------------------\n");
         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
         print_lock(hlock);
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 }
 
 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
                                 const void* lock_from, unsigned long lock_len)
 {
         return lock_from + lock_len <= mem_from ||
                 mem_from + mem_len <= lock_from;
 }
 
 /*
  * Called when kernel memory is freed (or unmapped), or if a lock
  * is destroyed or reinitialized - this code checks whether there is
  * any held lock in the memory range of <from> to <to>:
  */
 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
 {
         struct task_struct *curr = current;
         struct held_lock *hlock;
         unsigned long flags;
         int i;
 
         if (unlikely(!debug_locks))
                 return;
 
         local_irq_save(flags);
         for (i = 0; i < curr->lockdep_depth; i++) {
                 hlock = curr->held_locks + i;
 
                 if (not_in_range(mem_from, mem_len, hlock->instance,
                                         sizeof(*hlock->instance)))
                         continue;
 
                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
                 break;
         }
         local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
 
 static void print_held_locks_bug(struct task_struct *curr)
 {
         if (!debug_locks_off())
                 return;
         if (debug_locks_silent)
                 return;
 
         printk("\n=====================================\n");
         printk(  "[ BUG: lock held at task exit time! ]\n");
         printk(  "-------------------------------------\n");
         printk("%s/%d is exiting with locks still held!\n",
                 curr->comm, task_pid_nr(curr));
         lockdep_print_held_locks(curr);
 
         printk("\nstack backtrace:\n");
         dump_stack();
 }
 
 void debug_check_no_locks_held(struct task_struct *task)
 {
         if (unlikely(task->lockdep_depth > 0))
                 print_held_locks_bug(task);
 }
 
 void debug_show_all_locks(void)
 {
         struct task_struct *g, *p;
         int count = 10;
         int unlock = 1;
 
         if (unlikely(!debug_locks)) {
                 printk("INFO: lockdep is turned off.\n");
                 return;
         }
         printk("\nShowing all locks held in the system:\n");
 
         /*
          * Here we try to get the tasklist_lock as hard as possible,
          * if not successful after 2 seconds we ignore it (but keep
          * trying). This is to enable a debug printout even if a
          * tasklist_lock-holding task deadlocks or crashes.
          */
 retry:
         if (!read_trylock(&tasklist_lock)) {
                 if (count == 10)
                         printk("hm, tasklist_lock locked, retrying... ");
                 if (count) {
                         count--;
                         printk(" #%d", 10-count);
                         mdelay(200);
                         goto retry;
                 }
                 printk(" ignoring it.\n");
                 unlock = 0;
         }
         if (count != 10)
                 printk(" locked it.\n");
 
         do_each_thread(g, p) {
                 /*
                  * It's not reliable to print a task's held locks
                  * if it's not sleeping (or if it's not the current
                  * task):
                  */
                 if (p->state == TASK_RUNNING && p != current)
                         continue;
                 if (p->lockdep_depth)
                         lockdep_print_held_locks(p);
                 if (!unlock)
                         if (read_trylock(&tasklist_lock))
                                 unlock = 1;
         } while_each_thread(g, p);
 
         printk("\n");
         printk("=============================================\n\n");
 
         if (unlock)
                 read_unlock(&tasklist_lock);
 }
 
 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)
 {
         if (unlikely(!debug_locks)) {
                 printk("INFO: lockdep is turned off.\n");
                 return;
         }
         if (task == current)
                 lockdep_print_held_locks(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)
 {
         struct task_struct *curr = current;
 
         if (unlikely(curr->lockdep_depth)) {
                 if (!debug_locks_off())
                         return;
                 printk("\n================================================\n");
                 printk(  "[ BUG: lock held when returning to user space! ]\n");
                 printk(  "------------------------------------------------\n");
                 printk("%s/%d is leaving the kernel with locks still held!\n",
                                 curr->comm, curr->pid);
                 lockdep_print_held_locks(curr);
         }
 }