blob: c6d0c1dc625324cd8bbbaaf78f1c2709f30dd345 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
/*
* 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
*
* 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.
*/
#define DISABLE_BRANCH_PROFILING
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/sched/task.h>
#include <linux/sched/mm.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 <linux/stringify.h>
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/gfp.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/nmi.h>
#include <linux/rcupdate.h>
#include <linux/kprobes.h>
#include <asm/sections.h>
#include "lockdep_internals.h"
#define CREATE_TRACE_POINTS
#include <trace/events/lock.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
DEFINE_PER_CPU(unsigned int, lockdep_recursion);
EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
static __always_inline bool lockdep_enabled(void)
{
if (!debug_locks)
return false;
if (this_cpu_read(lockdep_recursion))
return false;
if (current->lockdep_recursion)
return false;
return true;
}
/*
* 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 arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
static struct task_struct *__owner;
static inline void lockdep_lock(void)
{
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
__this_cpu_inc(lockdep_recursion);
arch_spin_lock(&__lock);
__owner = current;
}
static inline void lockdep_unlock(void)
{
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
return;
__owner = NULL;
arch_spin_unlock(&__lock);
__this_cpu_dec(lockdep_recursion);
}
static inline bool lockdep_assert_locked(void)
{
return DEBUG_LOCKS_WARN_ON(__owner != current);
}
static struct task_struct *lockdep_selftest_task_struct;
static int graph_lock(void)
{
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) {
lockdep_unlock();
return 0;
}
return 1;
}
static inline void graph_unlock(void)
{
lockdep_unlock();
}
/*
* 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();
lockdep_unlock();
return ret;
}
unsigned long nr_list_entries;
static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
/*
* All data structures here are protected by the global debug_lock.
*
* nr_lock_classes is the number of elements of lock_classes[] that is
* in use.
*/
#define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
#define KEYHASH_SIZE (1UL << KEYHASH_BITS)
static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
unsigned long nr_lock_classes;
unsigned long nr_zapped_classes;
#ifndef CONFIG_DEBUG_LOCKDEP
static
#endif
struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
static inline struct lock_class *hlock_class(struct held_lock *hlock)
{
unsigned int class_idx = hlock->class_idx;
/* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
barrier();
if (!test_bit(class_idx, lock_classes_in_use)) {
/*
* Someone passed in garbage, we give up.
*/
DEBUG_LOCKS_WARN_ON(1);
return NULL;
}
/*
* At this point, if the passed hlock->class_idx is still garbage,
* we just have to live with it
*/
return lock_classes + class_idx;
}
#ifdef CONFIG_LOCK_STAT
static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
static inline u64 lockstat_clock(void)
{
return local_clock();
}
static int lock_point(unsigned long points[], unsigned long ip)
{
int i;
for (i = 0; i < LOCKSTAT_POINTS; i++) {
if (points[i] == 0) {
points[i] = ip;
break;
}
if (points[i] == ip)
break;
}
return i;
}
static void lock_time_inc(struct lock_time *lt, u64 time)
{
if (time > lt->max)
lt->max = time;
if (time < lt->min || !lt->nr)
lt->min = time;
lt->total += time;
lt->nr++;
}
static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
{
if (!src->nr)
return;
if (src->max > dst->max)
dst->max = src->max;
if (src->min < dst->min || !dst->nr)
dst->min = src->min;
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(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];
for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
stats.contending_point[i] += pcs->contending_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(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));
memset(class->contending_point, 0, sizeof(class->contending_point));
}
static struct lock_class_stats *get_lock_stats(struct lock_class *class)
{
return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
}
static void lock_release_holdtime(struct held_lock *hlock)
{
struct lock_class_stats *stats;
u64 holdtime;
if (!lock_stat)
return;
holdtime = lockstat_clock() - hlock->holdtime_stamp;
stats = get_lock_stats(hlock_class(hlock));
if (hlock->read)
lock_time_inc(&stats->read_holdtime, holdtime);
else
lock_time_inc(&stats->write_holdtime, holdtime);
}
#else
static inline void lock_release_holdtime(struct held_lock *hlock)
{
}
#endif
/*
* We keep a global list of all lock classes. The list is only accessed with
* the lockdep spinlock lock held. free_lock_classes is a list with free
* elements. These elements are linked together by the lock_entry member in
* struct lock_class.
*/
LIST_HEAD(all_lock_classes);
static LIST_HEAD(free_lock_classes);
/**
* struct pending_free - information about data structures about to be freed
* @zapped: Head of a list with struct lock_class elements.
* @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
* are about to be freed.
*/
struct pending_free {
struct list_head zapped;
DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
};
/**
* struct delayed_free - data structures used for delayed freeing
*
* A data structure for delayed freeing of data structures that may be
* accessed by RCU readers at the time these were freed.
*
* @rcu_head: Used to schedule an RCU callback for freeing data structures.
* @index: Index of @pf to which freed data structures are added.
* @scheduled: Whether or not an RCU callback has been scheduled.
* @pf: Array with information about data structures about to be freed.
*/
static struct delayed_free {
struct rcu_head rcu_head;
int index;
int scheduled;
struct pending_free pf[2];
} delayed_free;
/*
* 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 hlist_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 hlist_head chainhash_table[CHAINHASH_SIZE];
/*
* the id of held_lock
*/
static inline u16 hlock_id(struct held_lock *hlock)
{
BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
}
static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
{
return hlock_id & (MAX_LOCKDEP_KEYS - 1);
}
/*
* 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.
*/
static inline u64 iterate_chain_key(u64 key, u32 idx)
{
u32 k0 = key, k1 = key >> 32;
__jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
return k0 | (u64)k1 << 32;
}
void lockdep_init_task(struct task_struct *task)
{
task->lockdep_depth = 0; /* no locks held yet */
task->curr_chain_key = INITIAL_CHAIN_KEY;
task->lockdep_recursion = 0;
}
static __always_inline void lockdep_recursion_inc(void)
{
__this_cpu_inc(lockdep_recursion);
}
static __always_inline void lockdep_recursion_finish(void)
{
if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
__this_cpu_write(lockdep_recursion, 0);
}
void lockdep_set_selftest_task(struct task_struct *task)
{
lockdep_selftest_task_struct = task;
}
/*
* 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;
}
static void print_lockdep_off(const char *bug_msg)
{
printk(KERN_DEBUG "%s\n", bug_msg);
printk(KERN_DEBUG "turning off the locking correctness validator.\n");
#ifdef CONFIG_LOCK_STAT
printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
#endif
}
unsigned long nr_stack_trace_entries;
#ifdef CONFIG_PROVE_LOCKING
/**
* struct lock_trace - single stack backtrace
* @hash_entry: Entry in a stack_trace_hash[] list.
* @hash: jhash() of @entries.
* @nr_entries: Number of entries in @entries.
* @entries: Actual stack backtrace.
*/
struct lock_trace {
struct hlist_node hash_entry;
u32 hash;
u32 nr_entries;
unsigned long entries[] __aligned(sizeof(unsigned long));
};
#define LOCK_TRACE_SIZE_IN_LONGS \
(sizeof(struct lock_trace) / sizeof(unsigned long))
/*
* Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
*/
static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
{
return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
memcmp(t1->entries, t2->entries,
t1->nr_entries * sizeof(t1->entries[0])) == 0;
}
static struct lock_trace *save_trace(void)
{
struct lock_trace *trace, *t2;
struct hlist_head *hash_head;
u32 hash;
int max_entries;
BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
LOCK_TRACE_SIZE_IN_LONGS;
if (max_entries <= 0) {
if (!debug_locks_off_graph_unlock())
return NULL;
print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
dump_stack();
return NULL;
}
trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
hash = jhash(trace->entries, trace->nr_entries *
sizeof(trace->entries[0]), 0);
trace->hash = hash;
hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
hlist_for_each_entry(t2, hash_head, hash_entry) {
if (traces_identical(trace, t2))
return t2;
}
nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
hlist_add_head(&trace->hash_entry, hash_head);
return trace;
}
/* Return the number of stack traces in the stack_trace[] array. */
u64 lockdep_stack_trace_count(void)
{
struct lock_trace *trace;
u64 c = 0;
int i;
for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
c++;
}
}
return c;
}
/* Return the number of stack hash chains that have at least one stack trace. */
u64 lockdep_stack_hash_count(void)
{
u64 c = 0;
int i;
for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
if (!hlist_empty(&stack_trace_hash[i]))
c++;
return c;
}
#endif
unsigned int nr_hardirq_chains;
unsigned int nr_softirq_chains;
unsigned int nr_process_chains;
unsigned int max_lockdep_depth;
#ifdef CONFIG_DEBUG_LOCKDEP
/*
* Various lockdep statistics:
*/
DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
#endif
#ifdef CONFIG_PROVE_LOCKING
/*
* Locking printouts:
*/
#define __USAGE(__STATE) \
[LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
[LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
[LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
[LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
static const char *usage_str[] =
{
#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
#include "lockdep_states.h"
#undef LOCKDEP_STATE
[LOCK_USED] = "INITIAL USE",
[LOCK_USED_READ] = "INITIAL READ USE",
/* abused as string storage for verify_lock_unused() */
[LOCK_USAGE_STATES] = "IN-NMI",
};
#endif
const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
{
return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
}
static inline unsigned long lock_flag(enum lock_usage_bit bit)
{
return 1UL << bit;
}
static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
{
/*
* The usage character defaults to '.' (i.e., irqs disabled and not in
* irq context), which is the safest usage category.
*/
char c = '.';
/*
* The order of the following usage checks matters, which will
* result in the outcome character as follows:
*
* - '+': irq is enabled and not in irq context
* - '-': in irq context and irq is disabled
* - '?': in irq context and irq is enabled
*/
if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
c = '+';
if (class->usage_mask & lock_flag(bit))
c = '?';
} else if (class->usage_mask & lock_flag(bit))
c = '-';
return c;
}
void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
{
int i = 0;
#define LOCKDEP_STATE(__STATE) \
usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
#include "lockdep_states.h"
#undef LOCKDEP_STATE
usage[i] = '\0';
}
static void __print_lock_name(struct lock_class *class)
{
char str[KSYM_NAME_LEN];
const char *name;
name = class->name;
if (!name) {
name = __get_key_name(class->key, str);
printk(KERN_CONT "%s", name);
} else {
printk(KERN_CONT "%s", name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
if (class->subclass)
printk(KERN_CONT "/%d", class->subclass);
}
}
static void print_lock_name(struct lock_class *class)
{
char usage[LOCK_USAGE_CHARS];
get_usage_chars(class, usage);
printk(KERN_CONT " (");
__print_lock_name(class);
printk(KERN_CONT "){%s}-{%hd:%hd}", usage,
class->wait_type_outer ?: class->wait_type_inner,
class->wait_type_inner);
}
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(KERN_CONT "%s", name);
}
static void print_lock(struct held_lock *hlock)
{
/*
* We can be called locklessly through debug_show_all_locks() so be
* extra careful, the hlock might have been released and cleared.
*
* If this indeed happens, lets pretend it does not hurt to continue
* to print the lock unless the hlock class_idx does not point to a
* registered class. The rationale here is: since we don't attempt
* to distinguish whether we are in this situation, if it just
* happened we can't count on class_idx to tell either.
*/
struct lock_class *lock = hlock_class(hlock);
if (!lock) {
printk(KERN_CONT "<RELEASED>\n");
return;
}
printk(KERN_CONT "%px", hlock->instance);
print_lock_name(lock);
printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
}
static void lockdep_print_held_locks(struct task_struct *p)
{
int i, depth = READ_ONCE(p->lockdep_depth);
if (!depth)
printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
else
printk("%d lock%s held by %s/%d:\n", depth,
depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
/*
* It's not reliable to print a task's held locks if it's not sleeping
* and it's not the current task.
*/
if (p->state == TASK_RUNNING && p != current)
return;
for (i = 0; i < depth; i++) {
printk(" #%d: ", i);
print_lock(p->held_locks + i);
}
}
static void print_kernel_ident(void)
{
printk("%s %.*s %s\n", init_utsname()->release,
(int)strcspn(init_utsname()->version, " "),
init_utsname()->version,
print_tainted());
}
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:
*/
#ifdef __KERNEL__
static int static_obj(const void *obj)
{
unsigned long start = (unsigned long) &_stext,
end = (unsigned long) &_end,
addr = (unsigned long) obj;
if (arch_is_kernel_initmem_freed(addr))
return 0;
/*
* static variable?
*/
if ((addr >= start) && (addr < end))
return 1;
if (arch_is_kernel_data(addr))
return 1;
/*
* in-kernel percpu var?
*/
if (is_kernel_percpu_address(addr))
return 1;
/*
* module static or percpu var?
*/
return is_module_address(addr) || is_module_percpu_address(addr);
}
#endif
/*
* To make lock name printouts unique, we calculate a unique
* class->name_version generation counter. The caller must hold the graph
* lock.
*/
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;
}
/* used from NMI context -- must be lockless */
static __always_inline struct lock_class *
look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
{
struct lockdep_subclass_key *key;
struct hlist_head *hash_head;
struct lock_class *class;
if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
debug_locks_off();
printk(KERN_ERR
"BUG: looking up invalid subclass: %u\n", subclass);
printk(KERN_ERR
"turning off the locking correctness validator.\n");
dump_stack();
return NULL;
}
/*
* If it is not initialised then it has never been locked,
* so it won't be present in the hash table.
*/
if (unlikely(!lock->key))
return NULL;
/*
* 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 do an RCU walk of the hash, see lockdep_free_key_range().
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return NULL;
hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
if (class->key == key) {
/*
* Huh! same key, different name? Did someone trample
* on some memory? We're most confused.
*/
WARN_ON_ONCE(class->name != lock->name &&
lock->key != &__lockdep_no_validate__);
return class;
}
}
return NULL;
}
/*
* Static locks do not have their class-keys yet - for them the key is
* the lock object itself. If the lock is in the per cpu area, the
* canonical address of the lock (per cpu offset removed) is used.
*/
static bool assign_lock_key(struct lockdep_map *lock)
{
unsigned long can_addr, addr = (unsigned long)lock;
#ifdef __KERNEL__
/*
* lockdep_free_key_range() assumes that struct lock_class_key
* objects do not overlap. Since we use the address of lock
* objects as class key for static objects, check whether the
* size of lock_class_key objects does not exceed the size of
* the smallest lock object.
*/
BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
#endif
if (__is_kernel_percpu_address(addr, &can_addr))
lock->key = (void *)can_addr;
else if (__is_module_percpu_address(addr, &can_addr))
lock->key = (void *)can_addr;
else if (static_obj(lock))
lock->key = (void *)lock;
else {
/* Debug-check: all keys must be persistent! */
debug_locks_off();
pr_err("INFO: trying to register non-static key.\n");
pr_err("the code is fine but needs lockdep annotation.\n");
pr_err("turning off the locking correctness validator.\n");
dump_stack();
return false;
}
return true;
}
#ifdef CONFIG_DEBUG_LOCKDEP
/* Check whether element @e occurs in list @h */
static bool in_list(struct list_head *e, struct list_head *h)
{
struct list_head *f;
list_for_each(f, h) {
if (e == f)
return true;
}
return false;
}
/*
* Check whether entry @e occurs in any of the locks_after or locks_before
* lists.
*/
static bool in_any_class_list(struct list_head *e)
{
struct lock_class *class;
int i;
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
class = &lock_classes[i];
if (in_list(e, &class->locks_after) ||
in_list(e, &class->locks_before))
return true;
}
return false;
}
static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
{
struct lock_list *e;
list_for_each_entry(e, h, entry) {
if (e->links_to != c) {
printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
c->name ? : "(?)",
(unsigned long)(e - list_entries),
e->links_to && e->links_to->name ?
e->links_to->name : "(?)",
e->class && e->class->name ? e->class->name :
"(?)");
return false;
}
}
return true;
}
#ifdef CONFIG_PROVE_LOCKING
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
#endif
static bool check_lock_chain_key(struct lock_chain *chain)
{
#ifdef CONFIG_PROVE_LOCKING
u64 chain_key = INITIAL_CHAIN_KEY;
int i;
for (i = chain->base; i < chain->base + chain->depth; i++)
chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
/*
* The 'unsigned long long' casts avoid that a compiler warning
* is reported when building tools/lib/lockdep.
*/
if (chain->chain_key != chain_key) {
printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
(unsigned long long)(chain - lock_chains),
(unsigned long long)chain->chain_key,
(unsigned long long)chain_key);
return false;
}
#endif
return true;
}
static bool in_any_zapped_class_list(struct lock_class *class)
{
struct pending_free *pf;
int i;
for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
if (in_list(&class->lock_entry, &pf->zapped))
return true;
}
return false;
}
static bool __check_data_structures(void)
{
struct lock_class *class;
struct lock_chain *chain;
struct hlist_head *head;
struct lock_list *e;
int i;
/* Check whether all classes occur in a lock list. */
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
class = &lock_classes[i];
if (!in_list(&class->lock_entry, &all_lock_classes) &&
!in_list(&class->lock_entry, &free_lock_classes) &&
!in_any_zapped_class_list(class)) {
printk(KERN_INFO "class %px/%s is not in any class list\n",
class, class->name ? : "(?)");
return false;
}
}
/* Check whether all classes have valid lock lists. */
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
class = &lock_classes[i];
if (!class_lock_list_valid(class, &class->locks_before))
return false;
if (!class_lock_list_valid(class, &class->locks_after))
return false;
}
/* Check the chain_key of all lock chains. */
for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
head = chainhash_table + i;
hlist_for_each_entry_rcu(chain, head, entry) {
if (!check_lock_chain_key(chain))
return false;
}
}
/*
* Check whether all list entries that are in use occur in a class
* lock list.
*/
for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
e = list_entries + i;
if (!in_any_class_list(&e->entry)) {
printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
(unsigned int)(e - list_entries),
e->class->name ? : "(?)",
e->links_to->name ? : "(?)");
return false;
}
}
/*
* Check whether all list entries that are not in use do not occur in
* a class lock list.
*/
for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
e = list_entries + i;
if (in_any_class_list(&e->entry)) {
printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
(unsigned int)(e - list_entries),
e->class && e->class->name ? e->class->name :
"(?)",
e->links_to && e->links_to->name ?
e->links_to->name : "(?)");
return false;
}
}
return true;
}
int check_consistency = 0;
module_param(check_consistency, int, 0644);
static void check_data_structures(void)
{
static bool once = false;
if (check_consistency && !once) {
if (!__check_data_structures()) {
once = true;
WARN_ON(once);
}
}
}
#else /* CONFIG_DEBUG_LOCKDEP */
static inline void check_data_structures(void) { }
#endif /* CONFIG_DEBUG_LOCKDEP */
static void init_chain_block_buckets(void);
/*
* Initialize the lock_classes[] array elements, the free_lock_classes list
* and also the delayed_free structure.
*/
static void init_data_structures_once(void)
{
static bool __read_mostly ds_initialized, rcu_head_initialized;
int i;
if (likely(rcu_head_initialized))
return;
if (system_state >= SYSTEM_SCHEDULING) {
init_rcu_head(&delayed_free.rcu_head);
rcu_head_initialized = true;
}
if (ds_initialized)
return;
ds_initialized = true;
INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
INIT_LIST_HEAD(&lock_classes[i].locks_after);
INIT_LIST_HEAD(&lock_classes[i].locks_before);
}
init_chain_block_buckets();
}
static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
{
unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
return lock_keys_hash + hash;
}
/* Register a dynamically allocated key. */
void lockdep_register_key(struct lock_class_key *key)
{
struct hlist_head *hash_head;
struct lock_class_key *k;
unsigned long flags;
if (WARN_ON_ONCE(static_obj(key)))
return;
hash_head = keyhashentry(key);
raw_local_irq_save(flags);
if (!graph_lock())
goto restore_irqs;
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (WARN_ON_ONCE(k == key))
goto out_unlock;
}
hlist_add_head_rcu(&key->hash_entry, hash_head);
out_unlock:
graph_unlock();
restore_irqs:
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lockdep_register_key);
/* Check whether a key has been registered as a dynamic key. */
static bool is_dynamic_key(const struct lock_class_key *key)
{
struct hlist_head *hash_head;
struct lock_class_key *k;
bool found = false;
if (WARN_ON_ONCE(static_obj(key)))
return false;
/*
* If lock debugging is disabled lock_keys_hash[] may contain
* pointers to memory that has already been freed. Avoid triggering
* a use-after-free in that case by returning early.
*/
if (!debug_locks)
return true;
hash_head = keyhashentry(key);
rcu_read_lock();
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (k == key) {
found = true;
break;
}
}
rcu_read_unlock();
return found;
}
/*
* 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 struct lock_class *
register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
{
struct lockdep_subclass_key *key;
struct hlist_head *hash_head;
struct lock_class *class;
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
class = look_up_lock_class(lock, subclass);
if (likely(class))
goto out_set_class_cache;
if (!lock->key) {
if (!assign_lock_key(lock))
return NULL;
} else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
return NULL;
}
key = lock->key->subkeys + subclass;
hash_head = classhashentry(key);
if (!graph_lock()) {
return NULL;
}
/*
* We have to do the hash-walk again, to avoid races
* with another CPU:
*/
hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
if (class->key == key)
goto out_unlock_set;
}
init_data_structures_once();
/* Allocate a new lock class and add it to the hash. */
class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
lock_entry);
if (!class) {
if (!debug_locks_off_graph_unlock()) {
return NULL;
}
print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
dump_stack();
return NULL;
}
nr_lock_classes++;
__set_bit(class - lock_classes, lock_classes_in_use);
debug_atomic_inc(nr_unused_locks);
class->key = key;
class->name = lock->name;
class->subclass = subclass;
WARN_ON_ONCE(!list_empty(&class->locks_before));
WARN_ON_ONCE(!list_empty(&class->locks_after));
class->name_version = count_matching_names(class);
class->wait_type_inner = lock->wait_type_inner;
class->wait_type_outer = lock->wait_type_outer;
class->lock_type = lock->lock_type;
/*
* We use RCU's safe list-add method to make
* parallel walking of the hash-list safe:
*/
hlist_add_head_rcu(&class->hash_entry, hash_head);
/*
* Remove the class from the free list and add it to the global list
* of classes.
*/
list_move_tail(&class->lock_entry, &all_lock_classes);
if (verbose(class)) {
graph_unlock();
printk("\nnew class %px: %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
if (!graph_lock()) {
return NULL;
}
}
out_unlock_set:
graph_unlock();
out_set_class_cache:
if (!subclass || force)
lock->class_cache[0] = class;
else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
lock->class_cache[subclass] = class;
/*
* Hash collision, did we smoke some? We found a class with a matching
* hash but the subclass -- which is hashed in -- didn't match.
*/
if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
return NULL;
return class;
}
#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)
{
int idx = find_first_zero_bit(list_entries_in_use,
ARRAY_SIZE(list_entries));
if (idx >= ARRAY_SIZE(list_entries)) {
if (!debug_locks_off_graph_unlock())
return NULL;
print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
dump_stack();
return NULL;
}
nr_list_entries++;
__set_bit(idx, list_entries_in_use);
return list_entries + idx;
}
/*
* Add a new dependency to the head of the list:
*/
static int add_lock_to_list(struct lock_class *this,
struct lock_class *links_to, struct list_head *head,
unsigned long ip, u16 distance, u8 dep,
const struct lock_trace *trace)
{
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->links_to = links_to;
entry->dep = dep;
entry->distance = distance;
entry->trace = trace;
/*
* Both allocation and removal are done under the graph lock; but
* iteration is under RCU-sched; see look_up_lock_class() and
* lockdep_free_key_range().
*/
list_add_tail_rcu(&entry->entry, head);
return 1;
}
/*
* For good efficiency of modular, we use power of 2
*/
#define MAX_CIRCULAR_QUEUE_SIZE 4096UL
#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
/*
* The circular_queue and helpers are used to implement graph
* breadth-first search (BFS) algorithm, by which we can determine
* whether there is a path from a lock to another. In deadlock checks,
* a path from the next lock to be acquired to a previous held lock
* indicates that adding the <prev> -> <next> lock dependency will
* produce a circle in the graph. Breadth-first search instead of
* depth-first search is used in order to find the shortest (circular)
* path.
*/
struct circular_queue {
struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
unsigned int front, rear;
};
static struct circular_queue lock_cq;
unsigned int max_bfs_queue_depth;
static unsigned int lockdep_dependency_gen_id;
static inline void __cq_init(struct circular_queue *cq)
{
cq->front = cq->rear = 0;
lockdep_dependency_gen_id++;
}
static inline int __cq_empty(struct circular_queue *cq)
{
return (cq->front == cq->rear);
}
static inline int __cq_full(struct circular_queue *cq)
{
return ((cq->rear + 1) & CQ_MASK) == cq->front;
}
static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
{
if (__cq_full(cq))
return -1;
cq->element[cq->rear] = elem;
cq->rear = (cq->rear + 1) & CQ_MASK;
return 0;
}
/*
* Dequeue an element from the circular_queue, return a lock_list if
* the queue is not empty, or NULL if otherwise.
*/
static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
{
struct lock_list * lock;
if (__cq_empty(cq))
return NULL;
lock = cq->element[cq->front];
cq->front = (cq->front + 1) & CQ_MASK;
return lock;
}
static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
{
return (cq->rear - cq->front) & CQ_MASK;
}
static inline void mark_lock_accessed(struct lock_list *lock)
{
lock->class->dep_gen_id = lockdep_dependency_gen_id;
}
static inline void visit_lock_entry(struct lock_list *lock,
struct lock_list *parent)
{
lock->parent = parent;
}
static inline unsigned long lock_accessed(struct lock_list *lock)
{
return lock->class->dep_gen_id == lockdep_dependency_gen_id;
}
static inline struct lock_list *get_lock_parent(struct lock_list *child)
{
return child->parent;
}
static inline int get_lock_depth(struct lock_list *child)
{
int depth = 0;
struct lock_list *parent;
while ((parent = get_lock_parent(child))) {
child = parent;
depth++;
}
return depth;
}
/*
* Return the forward or backward dependency list.
*
* @lock: the lock_list to get its class's dependency list
* @offset: the offset to struct lock_class to determine whether it is
* locks_after or locks_before
*/
static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
{
void *lock_class = lock->class;
return lock_class + offset;
}
/*
* Return values of a bfs search:
*
* BFS_E* indicates an error
* BFS_R* indicates a result (match or not)
*
* BFS_EINVALIDNODE: Find a invalid node in the graph.
*
* BFS_EQUEUEFULL: The queue is full while doing the bfs.
*
* BFS_RMATCH: Find the matched node in the graph, and put that node into
* *@target_entry.
*
* BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
* _unchanged_.
*/
enum bfs_result {
BFS_EINVALIDNODE = -2,
BFS_EQUEUEFULL = -1,
BFS_RMATCH = 0,
BFS_RNOMATCH = 1,
};
/*
* bfs_result < 0 means error
*/
static inline bool bfs_error(enum bfs_result res)
{
return res < 0;
}
/*
* DEP_*_BIT in lock_list::dep
*
* For dependency @prev -> @next:
*
* SR: @prev is shared reader (->read != 0) and @next is recursive reader
* (->read == 2)
* ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
* SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
* EN: @prev is exclusive locker and @next is non-recursive locker
*
* Note that we define the value of DEP_*_BITs so that:
* bit0 is prev->read == 0
* bit1 is next->read != 2
*/
#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
#define DEP_SR_MASK (1U << (DEP_SR_BIT))
#define DEP_ER_MASK (1U << (DEP_ER_BIT))
#define DEP_SN_MASK (1U << (DEP_SN_BIT))
#define DEP_EN_MASK (1U << (DEP_EN_BIT))
static inline unsigned int
__calc_dep_bit(struct held_lock *prev, struct held_lock *next)
{
return (prev->read == 0) + ((next->read != 2) << 1);
}
static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
{
return 1U << __calc_dep_bit(prev, next);
}
/*
* calculate the dep_bit for backwards edges. We care about whether @prev is
* shared and whether @next is recursive.
*/
static inline unsigned int
__calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
{
return (next->read != 2) + ((prev->read == 0) << 1);
}
static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
{
return 1U << __calc_dep_bitb(prev, next);
}
/*
* Initialize a lock_list entry @lock belonging to @class as the root for a BFS
* search.
*/
static inline void __bfs_init_root(struct lock_list *lock,
struct lock_class *class)
{
lock->class = class;
lock->parent = NULL;
lock->only_xr = 0;
}
/*
* Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
* root for a BFS search.
*
* ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
* that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
* and -(S*)->.
*/
static inline void bfs_init_root(struct lock_list *lock,
struct held_lock *hlock)
{
__bfs_init_root(lock, hlock_class(hlock));
lock->only_xr = (hlock->read == 2);
}
/*
* Similar to bfs_init_root() but initialize the root for backwards BFS.
*
* ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
* that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
* -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
*/
static inline void bfs_init_rootb(struct lock_list *lock,
struct held_lock *hlock)
{
__bfs_init_root(lock, hlock_class(hlock));
lock->only_xr = (hlock->read != 0);
}
static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
{
if (!lock || !lock->parent)
return NULL;
return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
&lock->entry, struct lock_list, entry);
}
/*
* Breadth-First Search to find a strong path in the dependency graph.
*
* @source_entry: the source of the path we are searching for.
* @data: data used for the second parameter of @match function
* @match: match function for the search
* @target_entry: pointer to the target of a matched path
* @offset: the offset to struct lock_class to determine whether it is
* locks_after or locks_before
*
* We may have multiple edges (considering different kinds of dependencies,
* e.g. ER and SN) between two nodes in the dependency graph. But
* only the strong dependency path in the graph is relevant to deadlocks. A
* strong dependency path is a dependency path that doesn't have two adjacent
* dependencies as -(*R)-> -(S*)->, please see:
*
* Documentation/locking/lockdep-design.rst
*
* for more explanation of the definition of strong dependency paths
*
* In __bfs(), we only traverse in the strong dependency path:
*
* In lock_list::only_xr, we record whether the previous dependency only
* has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
* filter out any -(S*)-> in the current dependency and after that, the
* ->only_xr is set according to whether we only have -(*R)-> left.
*/
static enum bfs_result __bfs(struct lock_list *source_entry,
void *data,
bool (*match)(struct lock_list *entry, void *data),
bool (*skip)(struct lock_list *entry, void *data),
struct lock_list **target_entry,
int offset)
{
struct circular_queue *cq = &lock_cq;
struct lock_list *lock = NULL;
struct lock_list *entry;
struct list_head *head;
unsigned int cq_depth;
bool first;
lockdep_assert_locked();
__cq_init(cq);
__cq_enqueue(cq, source_entry);
while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
if (!lock->class)
return BFS_EINVALIDNODE;
/*
* Step 1: check whether we already finish on this one.
*
* If we have visited all the dependencies from this @lock to
* others (iow, if we have visited all lock_list entries in
* @lock->class->locks_{after,before}) we skip, otherwise go
* and visit all the dependencies in the list and mark this
* list accessed.
*/
if (lock_accessed(lock))
continue;
else
mark_lock_accessed(lock);
/*
* Step 2: check whether prev dependency and this form a strong
* dependency path.
*/
if (lock->parent) { /* Parent exists, check prev dependency */
u8 dep = lock->dep;
bool prev_only_xr = lock->parent->only_xr;
/*
* Mask out all -(S*)-> if we only have *R in previous
* step, because -(*R)-> -(S*)-> don't make up a strong
* dependency.
*/
if (prev_only_xr)
dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
/* If nothing left, we skip */
if (!dep)
continue;
/* If there are only -(*R)-> left, set that for the next step */
lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
}
/*
* Step 3: we haven't visited this and there is a strong
* dependency path to this, so check with @match.
* If @skip is provide and returns true, we skip this
* lock (and any path this lock is in).
*/
if (skip && skip(lock, data))
continue;
if (match(lock, data)) {
*target_entry = lock;
return BFS_RMATCH;
}
/*
* Step 4: if not match, expand the path by adding the
* forward or backwards dependencis in the search
*
*/
first = true;
head = get_dep_list(lock, offset);
list_for_each_entry_rcu(entry, head, entry) {
visit_lock_entry(entry, lock);
/*
* Note we only enqueue the first of the list into the
* queue, because we can always find a sibling
* dependency from one (see __bfs_next()), as a result
* the space of queue is saved.
*/
if (!first)
continue;
first = false;
if (__cq_enqueue(cq, entry))
return BFS_EQUEUEFULL;
cq_depth = __cq_get_elem_count(cq);
if (max_bfs_queue_depth < cq_depth)
max_bfs_queue_depth = cq_depth;
}
}
return BFS_RNOMATCH;
}
static inline enum bfs_result
__bfs_forwards(struct lock_list *src_entry,
void *data,
bool (*match)(struct lock_list *entry, void *data),
bool (*skip)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
{
return __bfs(src_entry, data, match, skip, target_entry,
offsetof(struct lock_class, locks_after));
}
static inline enum bfs_result
__bfs_backwards(struct lock_list *src_entry,
void *data,
bool (*match)(struct lock_list *entry, void *data),
bool (*skip)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
{
return __bfs(src_entry, data, match, skip, target_entry,
offsetof(struct lock_class, locks_before));
}
static void print_lock_trace(const struct lock_trace *trace,
unsigned int spaces)
{
stack_trace_print(trace->entries, trace->nr_entries, spaces);
}
/*
* Print a dependency chain entry (this is only done when a deadlock
* has been detected):
*/
static noinline void
print_circular_bug_entry(struct lock_list *target, int depth)
{
if (debug_locks_silent)
return;
printk("\n-> #%u", depth);
print_lock_name(target->class);
printk(KERN_CONT ":\n");
print_lock_trace(target->trace, 6);
}
static void
print_circular_lock_scenario(struct held_lock *src,
struct held_lock *tgt,
struct lock_list *prt)
{
struct lock_class *source = hlock_class(src);
struct lock_class *target = hlock_class(tgt);
struct lock_class *parent = prt->class;
/*
* A direct locking problem where unsafe_class lock is taken
* directly by safe_class lock, then all we need to show
* is the deadlock scenario, as it is obvious that the
* unsafe lock is taken under the safe lock.
*
* But if there is a chain instead, where the safe lock takes
* an intermediate lock (middle_class) where this lock is
* not the same as the safe lock, then the lock chain is
* used to describe the problem. Otherwise we would need
* to show a different CPU case for each link in the chain
* from the safe_class lock to the unsafe_class lock.
*/
if (parent != source) {
printk("Chain exists of:\n ");
__print_lock_name(source);
printk(KERN_CONT " --> ");
__print_lock_name(parent);
printk(KERN_CONT " --> ");
__print_lock_name(target);
printk(KERN_CONT "\n\n");
}
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
__print_lock_name(target);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(parent);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(target);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(source);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
/*
* When a circular dependency is detected, print the
* header first:
*/
static noinline void
print_circular_bug_header(struct lock_list *entry, unsigned int depth,
struct held_lock *check_src,
struct held_lock *check_tgt)
{
struct task_struct *curr = current;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("======================================================\n");
pr_warn("WARNING: possible circular locking dependency detected\n");
print_kernel_ident();
pr_warn("------------------------------------------------------\n");
pr_warn("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(check_src);
pr_warn("\nbut task is already holding lock:\n");
print_lock(check_tgt);
pr_warn("\nwhich lock already depends on the new lock.\n\n");
pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
print_circular_bug_entry(entry, depth);
}
/*
* We are about to add A -> B into the dependency graph, and in __bfs() a
* strong dependency path A -> .. -> B is found: hlock_class equals
* entry->class.
*
* If A -> .. -> B can replace A -> B in any __bfs() search (means the former
* is _stronger_ than or equal to the latter), we consider A -> B as redundant.
* For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
* -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
* dependency graph, as any strong path ..-> A -> B ->.. we can get with
* having dependency A -> B, we could already get a equivalent path ..-> A ->
* .. -> B -> .. with A -> .. -> B. Therefore A -> B is reduntant.
*
* We need to make sure both the start and the end of A -> .. -> B is not
* weaker than A -> B. For the start part, please see the comment in
* check_redundant(). For the end part, we need:
*
* Either
*
* a) A -> B is -(*R)-> (everything is not weaker than that)
*
* or
*
* b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
*
*/
static inline bool hlock_equal(struct lock_list *entry, void *data)
{
struct held_lock *hlock = (struct held_lock *)data;
return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
(hlock->read == 2 || /* A -> B is -(*R)-> */
!entry->only_xr); /* A -> .. -> B is -(*N)-> */
}
/*
* We are about to add B -> A into the dependency graph, and in __bfs() a
* strong dependency path A -> .. -> B is found: hlock_class equals
* entry->class.
*
* We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
* dependency cycle, that means:
*
* Either
*
* a) B -> A is -(E*)->
*
* or
*
* b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
*
* as then we don't have -(*R)-> -(S*)-> in the cycle.
*/
static inline bool hlock_conflict(struct lock_list *entry, void *data)
{
struct held_lock *hlock = (struct held_lock *)data;
return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
(hlock->read == 0 || /* B -> A is -(E*)-> */
!entry->only_xr); /* A -> .. -> B is -(*N)-> */
}
static noinline void print_circular_bug(struct lock_list *this,
struct lock_list *target,
struct held_lock *check_src,
struct held_lock *check_tgt)
{
struct task_struct *curr = current;
struct lock_list *parent;
struct lock_list *first_parent;
int depth;
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
this->trace = save_trace();
if (!this->trace)
return;
depth = get_lock_depth(target);
print_circular_bug_header(target, depth, check_src, check_tgt);
parent = get_lock_parent(target);
first_parent = parent;
while (parent) {
print_circular_bug_entry(parent, --depth);
parent = get_lock_parent(parent);
}
printk("\nother info that might help us debug this:\n\n");
print_circular_lock_scenario(check_src, check_tgt,
first_parent);
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
dump_stack();
}
static noinline void print_bfs_bug(int ret)
{
if (!debug_locks_off_graph_unlock())
return;
/*
* Breadth-first-search failed, graph got corrupted?
*/
WARN(1, "lockdep bfs error:%d\n", ret);
}
static bool noop_count(struct lock_list *entry, void *data)
{
(*(unsigned long *)data)++;
return false;
}
static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
{
unsigned long count = 0;
struct lock_list *target_entry;
__bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
return count;
}
unsigned long lockdep_count_forward_deps(struct lock_class *class)
{
unsigned long ret, flags;
struct lock_list this;
__bfs_init_root(&this, class);
raw_local_irq_save(flags);
lockdep_lock();
ret = __lockdep_count_forward_deps(&this);
lockdep_unlock();
raw_local_irq_restore(flags);
return ret;
}
static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
{
unsigned long count = 0;
struct lock_list *target_entry;
__bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
return count;
}
unsigned long lockdep_count_backward_deps(struct lock_class *class)
{
unsigned long ret, flags;
struct lock_list this;
__bfs_init_root(&this, class);
raw_local_irq_save(flags);
lockdep_lock();
ret = __lockdep_count_backward_deps(&this);
lockdep_unlock();
raw_local_irq_restore(flags);
return ret;
}
/*
* Check that the dependency graph starting at <src> can lead to
* <target> or not.
*/
static noinline enum bfs_result
check_path(struct held_lock *target, struct lock_list *src_entry,
bool (*match)(struct lock_list *entry, void *data),
bool (*skip)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
{
enum bfs_result ret;
ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
if (unlikely(bfs_error(ret)))
print_bfs_bug(ret);
return ret;
}
/*
* Prove that the dependency graph starting at <src> can not
* lead to <target>. If it can, there is a circle when adding
* <target> -> <src> dependency.
*
* Print an error and return BFS_RMATCH if it does.
*/
static noinline enum bfs_result
check_noncircular(struct held_lock *src, struct held_lock *target,
struct lock_trace **const trace)
{
enum bfs_result ret;
struct lock_list *target_entry;
struct lock_list src_entry;
bfs_init_root(&src_entry, src);
debug_atomic_inc(nr_cyclic_checks);
ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
if (unlikely(ret == BFS_RMATCH)) {
if (!*trace) {
/*
* If save_trace fails here, the printing might
* trigger a WARN but because of the !nr_entries it
* should not do bad things.
*/
*trace = save_trace();
}
print_circular_bug(&src_entry, target_entry, src, target);
}
return ret;
}
#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.
*
* A irq safe->unsafe deadlock happens with the following conditions:
*
* 1) We have a strong dependency path A -> ... -> B
*
* 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
* irq can create a new dependency B -> A (consider the case that a holder
* of B gets interrupted by an irq whose handler will try to acquire A).
*
* 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
* strong circle:
*
* For the usage bits of B:
* a) if A -> B is -(*N)->, then B -> A could be any type, so any
* ENABLED_IRQ usage suffices.
* b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
* ENABLED_IRQ_*_READ usage suffices.
*
* For the usage bits of A:
* c) if A -> B is -(E*)->, then B -> A could be any type, so any
* USED_IN_IRQ usage suffices.
* d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
* USED_IN_IRQ_*_READ usage suffices.
*/
/*
* There is a strong dependency path in the dependency graph: A -> B, and now
* we need to decide which usage bit of A should be accumulated to detect
* safe->unsafe bugs.
*
* Note that usage_accumulate() is used in backwards search, so ->only_xr
* stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
*
* As above, if only_xr is false, which means A -> B has -(E*)-> dependency
* path, any usage of A should be considered. Otherwise, we should only
* consider _READ usage.
*/
static inline bool usage_accumulate(struct lock_list *entry, void *mask)
{
if (!entry->only_xr)
*(unsigned long *)mask |= entry->class->usage_mask;
else /* Mask out _READ usage bits */
*(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
return false;
}
/*
* There is a strong dependency path in the dependency graph: A -> B, and now
* we need to decide which usage bit of B conflicts with the usage bits of A,
* i.e. which usage bit of B may introduce safe->unsafe deadlocks.
*
* As above, if only_xr is false, which means A -> B has -(*N)-> dependency
* path, any usage of B should be considered. Otherwise, we should only
* consider _READ usage.
*/
static inline bool usage_match(struct lock_list *entry, void *mask)
{
if (!entry->only_xr)
return !!(entry->class->usage_mask & *(unsigned long *)mask);
else /* Mask out _READ usage bits */
return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
}
static inline bool usage_skip(struct lock_list *entry, void *mask)
{
/*
* Skip local_lock() for irq inversion detection.
*
* For !RT, local_lock() is not a real lock, so it won't carry any
* dependency.
*
* For RT, an irq inversion happens when we have lock A and B, and on
* some CPU we can have:
*
* lock(A);
* <interrupted>
* lock(B);
*
* where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
*
* Now we prove local_lock() cannot exist in that dependency. First we
* have the observation for any lock chain L1 -> ... -> Ln, for any
* 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
* wait context check will complain. And since B is not a sleep lock,
* therefore B.inner_wait_type >= 2, and since the inner_wait_type of
* local_lock() is 3, which is greater than 2, therefore there is no
* way the local_lock() exists in the dependency B -> ... -> A.
*
* As a result, we will skip local_lock(), when we search for irq
* inversion bugs.
*/
if (entry->class->lock_type == LD_LOCK_PERCPU) {
if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
return false;
return true;
}
return false;
}
/*
* Find a node in the forwards-direction dependency sub-graph starting
* at @root->class that matches @bit.
*
* Return BFS_MATCH if such a node exists in the subgraph, and put that node
* into *@target_entry.
*/
static enum bfs_result
find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
struct lock_list **target_entry)
{
enum bfs_result result;
debug_atomic_inc(nr_find_usage_forwards_checks);
result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
return result;
}
/*
* Find a node in the backwards-direction dependency sub-graph starting
* at @root->class that matches @bit.
*/
static enum bfs_result
find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
struct lock_list **target_entry)
{
enum bfs_result result;
debug_atomic_inc(nr_find_usage_backwards_checks);
result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
return result;
}
static void print_lock_class_header(struct lock_class *class, int depth)
{
int bit;
printk("%*s->", depth, "");
print_lock_name(class);
#ifdef CONFIG_DEBUG_LOCKDEP
printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
#endif
printk(KERN_CONT " {\n");
for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
if (class->usage_mask & (1 << bit)) {
int len = depth;
len += printk("%*s %s", depth, "", usage_str[bit]);
len += printk(KERN_CONT " at:\n");
print_lock_trace(class->usage_traces[bit], len);
}
}
printk("%*s }\n", depth, "");
printk("%*s ... key at: [<%px>] %pS\n",
depth, "", class->key, class->key);
}
/*
* printk the shortest lock dependencies from @start to @end in reverse order:
*/
static void __used
print_shortest_lock_dependencies(struct lock_list *leaf,
struct lock_list *root)
{
struct lock_list *entry = leaf;
int depth;
/*compute depth from generated tree by BFS*/
depth = get_lock_depth(leaf);
do {
print_lock_class_header(entry->class, depth);
printk("%*s ... acquired at:\n", depth, "");
print_lock_trace(entry->trace, 2);
printk("\n");
if (depth == 0 && (entry != root)) {
printk("lockdep:%s bad path found in chain graph\n", __func__);
break;
}
entry = get_lock_parent(entry);
depth--;
} while (entry && (depth >= 0));
}
static void
print_irq_lock_scenario(struct lock_list *safe_entry,
struct lock_list *unsafe_entry,
struct lock_class *prev_class,
struct lock_class *next_class)
{
struct lock_class *safe_class = safe_entry->class;
struct lock_class *unsafe_class = unsafe_entry->class;
struct lock_class *middle_class = prev_class;
if (middle_class == safe_class)
middle_class = next_class;
/*
* A direct locking problem where unsafe_class lock is taken
* directly by safe_class lock, then all we need to show
* is the deadlock scenario, as it is obvious that the
* unsafe lock is taken under the safe lock.
*
* But if there is a chain instead, where the safe lock takes
* an intermediate lock (middle_class) where this lock is
* not the same as the safe lock, then the lock chain is
* used to describe the problem. Otherwise we would need
* to show a different CPU case for each link in the chain
* from the safe_class lock to the unsafe_class lock.
*/
if (middle_class != unsafe_class) {
printk("Chain exists of:\n ");
__print_lock_name(safe_class);
printk(KERN_CONT " --> ");
__print_lock_name(middle_class);
printk(KERN_CONT " --> ");
__print_lock_name(unsafe_class);
printk(KERN_CONT "\n\n");
}
printk(" Possible interrupt unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
__print_lock_name(unsafe_class);
printk(KERN_CONT ");\n");
printk(" local_irq_disable();\n");
printk(" lock(");
__print_lock_name(safe_class);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(middle_class);
printk(KERN_CONT ");\n");
printk(" <Interrupt>\n");
printk(" lock(");
__print_lock_name(safe_class);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
static void
print_bad_irq_dependency(struct task_struct *curr,
struct lock_list *prev_root,
struct lock_list *next_root,
struct lock_list *backwards_entry,
struct lock_list *forwards_entry,
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;
pr_warn("\n");
pr_warn("=====================================================\n");
pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
irqclass, irqclass);
print_kernel_ident();
pr_warn("-----------------------------------------------------\n");
pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
curr->comm, task_pid_nr(curr),
lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
lockdep_hardirqs_enabled(),
curr->softirqs_enabled);
print_lock(next);
pr_warn("\nand this task is already holding:\n");
print_lock(prev);
pr_warn("which would create a new lock dependency:\n");
print_lock_name(hlock_class(prev));
pr_cont(" ->");
print_lock_name(hlock_class(next));
pr_cont("\n");
pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
irqclass);
print_lock_name(backwards_entry->class);
pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
print_lock_name(forwards_entry->class);
pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
pr_warn("...");
print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
pr_warn("\nother info that might help us debug this:\n\n");
print_irq_lock_scenario(backwards_entry, forwards_entry,
hlock_class(prev), hlock_class(next));
lockdep_print_held_locks(curr);
pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
prev_root->trace = save_trace();
if (!prev_root->trace)
return;
print_shortest_lock_dependencies(backwards_entry, prev_root);
pr_warn("\nthe dependencies between the lock to be acquired");
pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
next_root->trace = save_trace();
if (!next_root->trace)
return;
print_shortest_lock_dependencies(forwards_entry, next_root);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
static const char *state_names[] = {
#define LOCKDEP_STATE(__STATE) \
__stringify(__STATE),
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static const char *state_rnames[] = {
#define LOCKDEP_STATE(__STATE) \
__stringify(__STATE)"-READ",
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static inline const char *state_name(enum lock_usage_bit bit)
{
if (bit & LOCK_USAGE_READ_MASK)
return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
else
return state_names[bit >> LOCK_USAGE_DIR_MASK];
}
/*
* The bit number is encoded like:
*
* bit0: 0 exclusive, 1 read lock
* bit1: 0 used in irq, 1 irq enabled
* bit2-n: state
*/
static int exclusive_bit(int new_bit)
{
int state = new_bit & LOCK_USAGE_STATE_MASK;
int dir = new_bit & LOCK_USAGE_DIR_MASK;
/*
* keep state, bit flip the direction and strip read.
*/
return state | (dir ^ LOCK_USAGE_DIR_MASK);
}
/*
* Observe that when given a bitmask where each bitnr is encoded as above, a
* right shift of the mask transforms the individual bitnrs as -1 and
* conversely, a left shift transforms into +1 for the individual bitnrs.
*
* So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
* create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
* instead by subtracting the bit number by 2, or shifting the mask right by 2.
*
* Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
*
* So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
* all bits set) and recompose with bitnr1 flipped.
*/
static unsigned long invert_dir_mask(unsigned long mask)
{
unsigned long excl = 0;
/* Invert dir */
excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
return excl;
}
/*
* Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
* usage may cause deadlock too, for example:
*
* P1 P2
* <irq disabled>
* write_lock(l1); <irq enabled>
* read_lock(l2);
* write_lock(l2);
* <in irq>
* read_lock(l1);
*
* , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
* will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
* deadlock.
*
* In fact, all of the following cases may cause deadlocks:
*
* LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
* LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
* LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
* LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
*
* As a result, to calculate the "exclusive mask", first we invert the
* direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
* bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
* bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
*/
static unsigned long exclusive_mask(unsigned long mask)
{
unsigned long excl = invert_dir_mask(mask);
excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
return excl;
}
/*
* Retrieve the _possible_ original mask to which @mask is
* exclusive. Ie: this is the opposite of exclusive_mask().
* Note that 2 possible original bits can match an exclusive
* bit: one has LOCK_USAGE_READ_MASK set, the other has it
* cleared. So both are returned for each exclusive bit.
*/
static unsigned long original_mask(unsigned long mask)
{
unsigned long excl = invert_dir_mask(mask);
/* Include read in existing usages */
excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
return excl;
}
/*
* Find the first pair of bit match between an original
* usage mask and an exclusive usage mask.
*/
static int find_exclusive_match(unsigned long mask,
unsigned long excl_mask,
enum lock_usage_bit *bitp,
enum lock_usage_bit *excl_bitp)
{
int bit, excl, excl_read;
for_each_set_bit(bit, &mask, LOCK_USED) {
/*
* exclusive_bit() strips the read bit, however,
* LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
* to search excl | LOCK_USAGE_READ_MASK as well.
*/
excl = exclusive_bit(bit);
excl_read = excl | LOCK_USAGE_READ_MASK;
if (excl_mask & lock_flag(excl)) {
*bitp = bit;
*excl_bitp = excl;
return 0;
} else if (excl_mask & lock_flag(excl_read)) {
*bitp = bit;
*excl_bitp = excl_read;
return 0;
}
}
return -1;
}
/*
* 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>:
*/
static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next)
{
unsigned long usage_mask = 0, forward_mask, backward_mask;
enum lock_usage_bit forward_bit = 0, backward_bit = 0;
struct lock_list *target_entry1;
struct lock_list *target_entry;
struct lock_list this, that;
enum bfs_result ret;
/*
* Step 1: gather all hard/soft IRQs usages backward in an
* accumulated usage mask.
*/
bfs_init_rootb(&this, prev);
ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
usage_mask &= LOCKF_USED_IN_IRQ_ALL;
if (!usage_mask)
return 1;
/*
* Step 2: find exclusive uses forward that match the previous
* backward accumulated mask.
*/
forward_mask = exclusive_mask(usage_mask);
bfs_init_root(&that, next);
ret = find_usage_forwards(&that, forward_mask, &target_entry1);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
if (ret == BFS_RNOMATCH)
return 1;
/*
* Step 3: we found a bad match! Now retrieve a lock from the backward
* list whose usage mask matches the exclusive usage mask from the
* lock found on the forward list.
*/
backward_mask = original_mask(target_entry1->class->usage_mask);
ret = find_usage_backwards(&this, backward_mask, &target_entry);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
return 1;
/*
* Step 4: narrow down to a pair of incompatible usage bits
* and report it.
*/
ret = find_exclusive_match(target_entry->class->usage_mask,
target_entry1->class->usage_mask,
&backward_bit, &forward_bit);
if (DEBUG_LOCKS_WARN_ON(ret == -1))
return 1;
print_bad_irq_dependency(curr, &this, &that,
target_entry, target_entry1,
prev, next,
backward_bit, forward_bit,
state_name(backward_bit));
return 0;
}
#else
static inline int check_irq_usage(struct task_struct *curr,
struct held_lock *prev, struct held_lock *next)
{
return 1;
}
static inline bool usage_skip(struct lock_list *entry, void *mask)
{
return false;
}
#endif /* CONFIG_TRACE_IRQFLAGS */
#ifdef CONFIG_LOCKDEP_SMALL
/*
* Check that the dependency graph starting at <src> can lead to
* <target> or not. If it can, <src> -> <target> dependency is already
* in the graph.
*
* Return BFS_RMATCH if it does, or BFS_RMATCH if it does not, return BFS_E* if
* any error appears in the bfs search.
*/
static noinline enum bfs_result
check_redundant(struct held_lock *src, struct held_lock *target)
{
enum bfs_result ret;
struct lock_list *target_entry;
struct lock_list src_entry;
bfs_init_root(&src_entry, src);
/*
* Special setup for check_redundant().
*
* To report redundant, we need to find a strong dependency path that
* is equal to or stronger than <src> -> <target>. So if <src> is E,
* we need to let __bfs() only search for a path starting at a -(E*)->,
* we achieve this by setting the initial node's ->only_xr to true in
* that case. And if <prev> is S, we set initial ->only_xr to false
* because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
*/
src_entry.only_xr = src->read == 0;
debug_atomic_inc(nr_redundant_checks);
/*
* Note: we skip local_lock() for redundant check, because as the
* comment in usage_skip(), A -> local_lock() -> B and A -> B are not
* the same.
*/
ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
if (ret == BFS_RMATCH)
debug_atomic_inc(nr_redundant);
return ret;
}
#else
static inline enum bfs_result
check_redundant(struct held_lock *src, struct held_lock *target)
{
return BFS_RNOMATCH;
}
#endif
static void inc_chains(int irq_context)
{
if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
nr_hardirq_chains++;
else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
nr_softirq_chains++;
else
nr_process_chains++;
}
static void dec_chains(int irq_context)
{
if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
nr_hardirq_chains--;
else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
nr_softirq_chains--;
else
nr_process_chains--;
}
static void
print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
{
struct lock_class *next = hlock_class(nxt);
struct lock_class *prev = hlock_class(prv);
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0\n");
printk(" ----\n");
printk(" lock(");
__print_lock_name(prev);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(next);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
printk(" May be due to missing lock nesting notation\n\n");
}
static void
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;
pr_warn("\n");
pr_warn("============================================\n");
pr_warn("WARNING: possible recursive locking detected\n");
print_kernel_ident();
pr_warn("--------------------------------------------\n");
pr_warn("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(next);
pr_warn("\nbut task is already holding lock:\n");
print_lock(prev);
pr_warn("\nother info that might help us debug this:\n");
print_deadlock_scenario(next, prev);
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
/*
* 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 if another lock with the same
* lock class is held but nest_lock is also held, i.e. we rely on the
* nest_lock to avoid the deadlock.
*/
static int
check_deadlock(struct task_struct *curr, struct held_lock *next)
{
struct held_lock *prev;
struct held_lock *nest = NULL;
int i;
for (i = 0; i < curr->lockdep_depth; i++) {
prev = curr->held_locks + i;
if (prev->instance == next->nest_lock)
nest = prev;
if (hlock_class(prev) != hlock_class(next))
continue;
/*
* Allow read-after-read recursion of the same
* lock class (i.e. read_lock(lock)+read_lock(lock)):
*/
if ((next->read == 2) && prev->read)
continue;
/*
* We're holding the nest_lock, which serializes this lock's
* nesting behaviour.
*/
if (nest)
return 2;
print_deadlock_bug(curr, prev, next);
return 0;
}
return 1;
}
/*
* There was a chain-cache miss, and we are about to add a new dependency
* to a previous lock. We 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, u16 distance,
struct lock_trace **const trace)
{
struct lock_list *entry;
enum bfs_result ret;
if (!hlock_class(prev)->key || !hlock_class(next)->key) {
/*
* The warning statements below may trigger a use-after-free
* of the class name. It is better to trigger a use-after free
* and to have the class name most of the time instead of not
* having the class name available.
*/
WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
"Detected use-after-free of lock class %px/%s\n",
hlock_class(prev),
hlock_class(prev)->name);
WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
"Detected use-after-free of lock class %px/%s\n",
hlock_class(next),
hlock_class(next)->name);
return 2;
}
/*
* Prove that the new <prev> -> <next> dependency would not
* create a circular dependency in the graph. (We do this by
* a breadth-first search into the graph starting at <next>,
* and check whether we can reach <prev>.)
*
* The search is limited by the size of the circular queue (i.e.,
* MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
* in the graph whose neighbours are to be checked.
*/
ret = check_noncircular(next, prev, trace);
if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
return 0;
if (!check_irq_usage(curr, prev, next))
return 0;
/*
* 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, &hlock_class(prev)->locks_after, entry) {
if (entry->class == hlock_class(next)) {
if (distance == 1)
entry->distance = 1;
entry->dep |= calc_dep(prev, next);
/*
* Also, update the reverse dependency in @next's
* ->locks_before list.
*
* Here we reuse @entry as the cursor, which is fine
* because we won't go to the next iteration of the
* outer loop:
*
* For normal cases, we return in the inner loop.
*</