1 files changed, 2702 insertions, 0 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
new file mode 100644
index 000000000000..f32ca78c198d
--- /dev/null
+++ b/kernel/lockdep.c
@@ -0,0 +1,2702 @@
+/*
+ * kernel/lockdep.c
+ *
+ * Runtime locking correctness validator
+ *
+ * Started by Ingo Molnar:
+ *
+ *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@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 <asm/sections.h>
+
+#include "lockdep_internals.h"
+
+/*
+ * hash_lock: protects the lockdep hashes and 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 hash_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+
+static int lockdep_initialized;
+
+unsigned long nr_list_entries;
+static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
+
+/*
+ * Allocate a lockdep entry. (assumes hash_lock held, returns
+ * with NULL on failure)
+ */
+static struct lock_list *alloc_list_entry(void)
+{
+        if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
+                __raw_spin_unlock(&hash_lock);
+                debug_locks_off();
+                printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
+                printk("turning off the locking correctness validator.\n");
+                return NULL;
+        }
+        return list_entries + nr_list_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];
+
+/*
+ * 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 CLASSHASH_MASK          (CLASSHASH_SIZE - 1)
+#define __classhashfn(key)      ((((unsigned long)key >> CLASSHASH_BITS) + (unsigned long)key) & CLASSHASH_MASK)
+#define classhashentry(key)     (classhash_table + __classhashfn((key)))
+
+static struct list_head classhash_table[CLASSHASH_SIZE];
+
+unsigned long nr_lock_chains;
+static struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
+
+/*
+ * 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 CHAINHASH_MASK          (CHAINHASH_SIZE - 1)
+#define __chainhashfn(chain) \
+                (((chain >> CHAINHASH_BITS) + chain) & CHAINHASH_MASK)
+#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/2) ^ \
+        ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS/2)) ^ \
+        (key2))
+
+void lockdep_off(void)
+{
+        current->lockdep_recursion++;
+}
+
+EXPORT_SYMBOL(lockdep_off);
+
+void lockdep_on(void)
+{
+        current->lockdep_recursion--;
+}
+
+EXPORT_SYMBOL(lockdep_on);
+
+int lockdep_internal(void)
+{
+        return current->lockdep_recursion != 0;
+}
+
+EXPORT_SYMBOL(lockdep_internal);
+
+/*
+ * Debugging switches:
+ */
+
+#define VERBOSE                 0
+#ifdef VERBOSE
+# define VERY_VERBOSE           0
+#endif
+
+#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 (class->name_version == 1 &&
+                        !strcmp(class->name, "&rl->lock"))
+                return 1;
+        if (class->name_version == 1 &&
+                        !strcmp(class->name, "&ni->mrec_lock"))
+                return 1;
+        if (class->name_version == 1 &&
+                        !strcmp(class->name, "mft_ni_runlist_lock"))
+                return 1;
+        if (class->name_version == 1 &&
+                        !strcmp(class->name, "mft_ni_mrec_lock"))
+                return 1;
+        if (class->name_version == 1 &&
+                        !strcmp(class->name, "&vol->lcnbmp_lock"))
+                return 1;
+        return 0;
+}
+#endif
+
+static int verbose(struct lock_class *class)
+{
+#if VERBOSE
+        return class_filter(class);
+#endif
+        return 0;
+}
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+
+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;
+}
+
+#endif
+
+/*
+ * Stack-trace: tightly packed array of stack backtrace
+ * addresses. Protected by the hash_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;
+
+        save_stack_trace(trace, NULL, 0, 3);
+
+        trace->max_entries = trace->nr_entries;
+
+        nr_stack_trace_entries += trace->nr_entries;
+        if (DEBUG_LOCKS_WARN_ON(nr_stack_trace_entries > MAX_STACK_TRACE_ENTRIES))
+                return 0;
+
+        if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
+                __raw_spin_unlock(&hash_lock);
+                if (debug_locks_off()) {
+                        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;
+
+/*
+ * 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)
+{
+        unsigned long offs, size;
+        char *modname;
+
+        return kallsyms_lookup((unsigned long)key, &size, &offs, &modname, 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[128], 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[128];
+
+        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 = curr->lockdep_depth;
+
+        if (!depth) {
+                printk("no locks held by %s/%d.\n", curr->comm, curr->pid);
+                return;
+        }
+        printk("%d lock%s held by %s/%d:\n",
+                depth, depth > 1 ? "s" : "", curr->comm, curr->pid);
+
+        for (i = 0; i < depth; i++) {
+                printk(" #%d: ", i);
+                print_lock(curr->held_locks + i);
+        }
+}
+/*
+ * Helper to print a nice hierarchy of lock dependencies:
+ */
+static void print_spaces(int nr)
+{
+        int i;
+
+        for (i = 0; i < nr; i++)
+                printk("  ");
+}
+
+static void print_lock_class_header(struct lock_class *class, int depth)
+{
+        int bit;
+
+        print_spaces(depth);
+        printk("->");
+        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;
+
+                        print_spaces(depth);
+                        len += printk("   %s", usage_str[bit]);
+                        len += printk(" at:\n");
+                        print_stack_trace(class->usage_traces + bit, len);
+                }
+        }
+        print_spaces(depth);
+        printk(" }\n");
+
+        print_spaces(depth);
+        printk(" ... key      at: ");
+        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) {
+                DEBUG_LOCKS_WARN_ON(!entry->class);
+                print_lock_dependencies(entry->class, depth + 1);
+
+                print_spaces(depth);
+                printk(" ... acquired at:\n");
+                print_stack_trace(&entry->trace, 2);
+                printk("\n");
+        }
+}
+
+/*
+ * 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)
+{
+        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;
+        save_trace(&entry->trace);
+
+        /*
+         * 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;
+
+        __raw_spin_unlock(&hash_lock);
+        debug_locks_off();
+        if (debug_locks_silent)
+                return 0;
+
+        printk("\n=======================================================\n");
+        printk(  "[ INFO: possible circular locking dependency detected ]\n");
+        printk(  "-------------------------------------------------------\n");
+        printk("%s/%d is trying to acquire lock:\n",
+                curr->comm, curr->pid);
+        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;
+        save_trace(&this.trace);
+        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;
+}
+
+static int noinline print_infinite_recursion_bug(void)
+{
+        __raw_spin_unlock(&hash_lock);
+        DEBUG_LOCKS_WARN_ON(1);
+
+        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 >= 20)
+                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;
+}
+
+static int very_verbose(struct lock_class *class)
+{
+#if VERY_VERBOSE
+        return class_filter(class);
+#endif
+        return 0;
+}
+#ifdef CONFIG_TRACE_IRQFLAGS
+
+/*
+ * 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 >= 20)
+                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 (depth > max_recursion_depth)
+                max_recursion_depth = depth;
+        if (depth >= 20)
+                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;
+}
+
+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)
+{
+        __raw_spin_unlock(&hash_lock);
+        debug_locks_off();
+        if (debug_locks_silent)
+                return 0;
+
+        printk("\n======================================================\n");
+        printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
+                irqclass, irqclass);
+        printk(  "------------------------------------------------------\n");
+        printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
+                curr->comm, curr->pid,
+                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;
+}
+
+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);
+}
+
+#endif
+
+static int
+print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
+                   struct held_lock *next)
+{
+        debug_locks_off();
+        __raw_spin_unlock(&hash_lock);
+        if (debug_locks_silent)
+                return 0;
+
+        printk("\n=============================================\n");
+        printk(  "[ INFO: possible recursive locking detected ]\n");
+        printk(  "---------------------------------------------\n");
+        printk("%s/%d is trying to acquire lock:\n",
+                curr->comm, curr->pid);
+        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)
+{
+        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();
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+        /*
+         * 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;
+#endif
+        /*
+         * 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)
+                        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);
+        if (!ret)
+                return 0;
+        /*
+         * Return value of 2 signals 'dependency already added',
+         * in that case we dont have to add the backlink either.
+         */
+        if (ret == 2)
+                return 2;
+        ret = add_lock_to_list(next->class, prev->class,
+                               &next->class->locks_before, next->acquire_ip);
+
+        /*
+         * Debugging printouts:
+         */
+        if (verbose(prev->class) || verbose(next->class)) {
+                __raw_spin_unlock(&hash_lock);
+                printk("\n new dependency: ");
+                print_lock_name(prev->class);
+                printk(" => ");
+                print_lock_name(next->class);
+                printk("\n");
+                dump_stack();
+                __raw_spin_lock(&hash_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 (;;) {
+                hlock = curr->held_locks + depth-1;
+                /*
+                 * Only non-recursive-read entries get new dependencies
+                 * added:
+                 */
+                if (hlock->read != 2) {
+                        check_prev_add(curr, hlock, next);
+                        /*
+                         * 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:
+        __raw_spin_unlock(&hash_lock);
+        DEBUG_LOCKS_WARN_ON(1);
+
+        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_end   + 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;
+}
+
+extern void __error_too_big_MAX_LOCKDEP_SUBCLASSES(void);
+
+/*
+ * 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)
+{
+        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;
+        }
+#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.
+         */
+        if (sizeof(struct lock_class_key) > sizeof(struct lock_class))
+                __error_too_big_MAX_LOCKDEP_SUBCLASSES();
+
+        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)
+                        goto out_set;
+
+        /*
+         * 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;
+        }
+
+        __raw_spin_lock(&hash_lock);
+        /*
+         * 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) {
+                __raw_spin_unlock(&hash_lock);
+                debug_locks_off();
+                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);
+
+        if (verbose(class)) {
+                __raw_spin_unlock(&hash_lock);
+                printk("\nnew class %p: %s", class->key, class->name);
+                if (class->name_version > 1)
+                        printk("#%d", class->name_version);
+                printk("\n");
+                dump_stack();
+                __raw_spin_lock(&hash_lock);
+        }
+out_unlock_set:
+        __raw_spin_unlock(&hash_lock);
+
+out_set:
+        lock->class[subclass] = class;
+
+        DEBUG_LOCKS_WARN_ON(class->subclass != subclass);
+
+        return class;
+}
+
+/*
+ * Look up a dependency chain. If the key is not present yet then
+ * add it and return 0 - in this case the new dependency chain is
+ * validated. If the key is already hashed, return 1.
+ */
+static inline int lookup_chain_cache(u64 chain_key)
+{
+        struct list_head *hash_head = chainhashentry(chain_key);
+        struct lock_chain *chain;
+
+        DEBUG_LOCKS_WARN_ON(!irqs_disabled());
+        /*
+         * 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);
+                        /*
+                         * In the debugging case, force redundant checking
+                         * by returning 1:
+                         */
+#ifdef CONFIG_DEBUG_LOCKDEP
+                        __raw_spin_lock(&hash_lock);
+                        return 1;
+#endif
+                        return 0;
+                }
+        }
+        /*
+         * Allocate a new chain entry from the static array, and add
+         * it to the hash:
+         */
+        __raw_spin_lock(&hash_lock);
+        /*
+         * 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) {
+                        __raw_spin_unlock(&hash_lock);
+                        goto cache_hit;
+                }
+        }
+        if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
+                __raw_spin_unlock(&hash_lock);
+                debug_locks_off();
+                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);
+#ifdef CONFIG_TRACE_IRQFLAGS
+        if (current->hardirq_context)
+                nr_hardirq_chains++;
+        else {
+                if (current->softirq_context)
+                        nr_softirq_chains++;
+                else
+                        nr_process_chains++;
+        }
+#else
+        nr_process_chains++;
+#endif
+
+        return 1;
+}
+
+/*
+ * 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;
+                DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS);
+                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
+}
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+
+/*
+ * 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)
+{
+        __raw_spin_unlock(&hash_lock);
+        debug_locks_off();
+        if (debug_locks_silent)
+                return 0;
+
+        printk("\n=========================================================\n");
+        printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
+        printk(  "---------------------------------------------------------\n");
+        printk("%s/%d just changed the state of lock:\n",
+                curr->comm, curr->pid);
+        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);
+}
+
+static inline 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);
+}
+
+#else
+static inline void print_irqtrace_events(struct task_struct *curr)
+{
+}
+#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)
+{
+        __raw_spin_unlock(&hash_lock);
+        debug_locks_off();
+        if (debug_locks_silent)
+                return 0;
+
+        printk("\n=================================\n");
+        printk(  "[ INFO: inconsistent lock state ]\n");
+        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, curr->pid,
+                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;
+}
+
+#define STRICT_READ_CHECKS      1
+
+/*
+ * 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 long ip)
+{
+        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;
+
+        __raw_spin_lock(&hash_lock);
+        /*
+         * Make sure we didnt race:
+         */
+        if (unlikely(this->class->usage_mask & new_mask)) {
+                __raw_spin_unlock(&hash_lock);
+                return 1;
+        }
+
+        this->class->usage_mask |= new_mask;
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+        if (new_bit == LOCK_ENABLED_HARDIRQS ||
+                        new_bit == LOCK_ENABLED_HARDIRQS_READ)
+                ip = curr->hardirq_enable_ip;
+        else if (new_bit == LOCK_ENABLED_SOFTIRQS ||
+                        new_bit == LOCK_ENABLED_SOFTIRQS_READ)
+                ip = curr->softirq_enable_ip;
+#endif
+        if (!save_trace(this->class->usage_traces + new_bit))
+                return 0;
+
+        switch (new_bit) {
+#ifdef CONFIG_TRACE_IRQFLAGS
+        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;
+#endif
+        case LOCK_USED:
+                /*
+                 * Add it to the global list of classes:
+                 */
+                list_add_tail_rcu(&this->class->lock_entry, &all_lock_classes);
+                debug_atomic_dec(&nr_unused_locks);
+                break;
+        default:
+                debug_locks_off();
+                WARN_ON(1);
+                return 0;
+        }
+
+        __raw_spin_unlock(&hash_lock);
+
+        /*
+         * We must printk outside of the hash_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;
+}
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+/*
+ * Mark all held locks with a usage bit:
+ */
+static int
+mark_held_locks(struct task_struct *curr, int hardirq, unsigned long ip)
+{
+        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, ip))
+                        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(void)
+{
+        struct task_struct *curr = current;
+        unsigned long ip;
+
+        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, ip))
+                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, ip))
+                        return;
+
+        curr->hardirq_enable_ip = ip;
+        curr->hardirq_enable_event = ++curr->irq_events;
+        debug_atomic_inc(&hardirqs_on_events);
+}
+
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+/*
+ * Hardirqs were disabled:
+ */
+void trace_hardirqs_off(void)
+{
+        struct task_struct *curr = current;
+
+        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);
+
+/*
+ * 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, ip);
+}
+
+/*
+ * 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);
+}
+
+#endif
+
+/*
+ * 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)
+{
+        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;
+        memset(lock->class, 0, sizeof(lock->class[0])*MAX_LOCKDEP_SUBCLASSES);
+}
+
+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 held_lock *hlock;
+        struct lock_class *class;
+        unsigned int depth, id;
+        int chain_head = 0;
+        u64 chain_key;
+
+        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;
+        }
+
+        class = lock->class[subclass];
+        /* not cached yet? */
+        if (unlikely(!class)) {
+                class = register_lock_class(lock, subclass);
+                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;
+
+        if (check != 2)
+                goto out_calc_hash;
+#ifdef CONFIG_TRACE_IRQFLAGS
+        /*
+         * If non-trylock use in a hardirq or softirq context, then
+         * mark the lock as used in these contexts:
+         */
+        if (!trylock) {
+                if (read) {
+                        if (curr->hardirq_context)
+                                if (!mark_lock(curr, hlock,
+                                                LOCK_USED_IN_HARDIRQ_READ, ip))
+                                        return 0;
+                        if (curr->softirq_context)
+                                if (!mark_lock(curr, hlock,
+                                                LOCK_USED_IN_SOFTIRQ_READ, ip))
+                                        return 0;
+                } else {
+                        if (curr->hardirq_context)
+                                if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ, ip))
+                                        return 0;
+                        if (curr->softirq_context)
+                                if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ, ip))
+                                        return 0;
+                }
+        }
+        if (!hardirqs_off) {
+                if (read) {
+                        if (!mark_lock(curr, hlock,
+                                        LOCK_ENABLED_HARDIRQS_READ, ip))
+                                return 0;
+                        if (curr->softirqs_enabled)
+                                if (!mark_lock(curr, hlock,
+                                                LOCK_ENABLED_SOFTIRQS_READ, ip))
+                                        return 0;
+                } else {
+                        if (!mark_lock(curr, hlock,
+                                        LOCK_ENABLED_HARDIRQS, ip))
+                                return 0;
+                        if (curr->softirqs_enabled)
+                                if (!mark_lock(curr, hlock,
+                                                LOCK_ENABLED_SOFTIRQS, ip))
+                                        return 0;
+                }
+        }
+#endif
+        /* mark it as used: */
+        if (!mark_lock(curr, hlock, LOCK_USED, ip))
+                return 0;
+out_calc_hash:
+        /*
+         * Calculate the chain hash: it's the combined has 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;
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+        /*
+         * 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) {
+                        chain_key = 0;
+                        chain_head = 1;
+                }
+        }
+#endif
+        chain_key = iterate_chain_key(chain_key, id);
+        curr->curr_chain_key = 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
+         * hash_lock for us)
+         */
+        if (!trylock && (check == 2) && lookup_chain_cache(chain_key)) {
+                /*
+                 * 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, 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;
+                __raw_spin_unlock(&hash_lock);
+        }
+        curr->lockdep_depth++;
+        check_chain_key(curr);
+        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, curr->pid);
+        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;
+}
+
+/*
+ * 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:
+        /*
+         * 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;
+
+#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))
+                DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled);
+        else
+                DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled);
+
+        /*
+         * 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
+}
+
+/*
+ * 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(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(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);
+
+/*
+ * Used by the testsuite, sanitize the validator state
+ * after a simulated failure:
+ */
+
+void lockdep_reset(void)
+{
+        unsigned long flags;
+
+        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;
+        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(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;
+
+        raw_local_irq_save(flags);
+        __raw_spin_lock(&hash_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);
+        }
+
+        __raw_spin_unlock(&hash_lock);
+        raw_local_irq_restore(flags);
+}
+
+void lockdep_reset_lock(struct lockdep_map *lock)
+{
+        struct lock_class *class, *next, *entry;
+        struct list_head *head;
+        unsigned long flags;
+        int i, j;
+
+        raw_local_irq_save(flags);
+        __raw_spin_lock(&hash_lock);
+
+        /*
+         * Remove all classes this lock has:
+         */
+        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) {
+                        for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
+                                entry = lock->class[j];
+                                if (class == entry) {
+                                        zap_class(class);
+                                        lock->class[j] = NULL;
+                                        break;
+                                }
+                        }
+                }
+        }
+
+        /*
+         * Debug check: in the end all mapped classes should
+         * be gone.
+         */
+        for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
+                entry = lock->class[j];
+                if (!entry)
+                        continue;
+                __raw_spin_unlock(&hash_lock);
+                DEBUG_LOCKS_WARN_ON(1);
+                raw_local_irq_restore(flags);
+                return;
+        }
+
+        __raw_spin_unlock(&hash_lock);
+        raw_local_irq_restore(flags);
+}
+
+void __init 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:    %lu\n", MAX_LOCKDEP_SUBCLASSES);
+        printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
+        printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
+        printk("... CLASSHASH_SIZE:           %lu\n", CLASSHASH_SIZE);
+        printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
+        printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
+        printk("... CHAINHASH_SIZE:          %lu\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 didnt call lockdep_init() early enough?\n");
+#endif
+}
+
+static inline int in_range(const void *start, const void *addr, const void *end)
+{
+        return addr >= start && addr <= end;
+}
+
+static void
+print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
+                     const void *mem_to)
+{
+        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, curr->pid, mem_from, mem_to-1);
+        lockdep_print_held_locks(curr);
+
+        printk("\nstack backtrace:\n");
+        dump_stack();
+}
+
+/*
+ * 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)
+{
+        const void *mem_to = mem_from + mem_len, *lock_from, *lock_to;
+        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;
+
+                lock_from = (void *)hlock->instance;
+                lock_to = (void *)(hlock->instance + 1);
+
+                if (!in_range(mem_from, lock_from, mem_to) &&
+                                        !in_range(mem_from, lock_to, mem_to))
+                        continue;
+
+                print_freed_lock_bug(curr, mem_from, mem_to);
+                break;
+        }
+        local_irq_restore(flags);
+}
+
+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, curr->pid);
+        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;
+
+        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) {
+                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);
+
+void debug_show_held_locks(struct task_struct *task)
+{
+        lockdep_print_held_locks(task);
+}
+
+EXPORT_SYMBOL_GPL(debug_show_held_locks);
+