| // 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 <linux/lockdep.h> |
| #include <linux/context_tracking.h> |
| |
| #include <asm/sections.h> |
| |
| #include "lockdep_internals.h" |
| |
| #include <trace/events/lock.h> |
| |
| #ifdef CONFIG_PROVE_LOCKING |
| static int prove_locking = 1; |
| module_param(prove_locking, int, 0644); |
| #else |
| #define prove_locking 0 |
| #endif |
| |
| #ifdef CONFIG_LOCK_STAT |
| static int lock_stat = 1; |
| module_param(lock_stat, int, 0644); |
| #else |
| #define lock_stat 0 |
| #endif |
| |
| #ifdef CONFIG_SYSCTL |
| static struct ctl_table kern_lockdep_table[] = { |
| #ifdef CONFIG_PROVE_LOCKING |
| { |
| .procname = "prove_locking", |
| .data = &prove_locking, |
| .maxlen = sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec, |
| }, |
| #endif /* CONFIG_PROVE_LOCKING */ |
| #ifdef CONFIG_LOCK_STAT |
| { |
| .procname = "lock_stat", |
| .data = &lock_stat, |
| .maxlen = sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec, |
| }, |
| #endif /* CONFIG_LOCK_STAT */ |
| { } |
| }; |
| |
| static __init int kernel_lockdep_sysctls_init(void) |
| { |
| register_sysctl_init("kernel", kern_lockdep_table); |
| return 0; |
| } |
| late_initcall(kernel_lockdep_sysctls_init); |
| #endif /* CONFIG_SYSCTL */ |
| |
| 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; |
| unsigned long max_lock_class_idx; |
| struct lock_class lock_classes[MAX_LOCKDEP_KEYS]; |
| 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. |
| */ |
| static 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}-{%d:%d}", 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 != current && task_is_running(p)) |
| 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 addr = (unsigned long) obj; |
| |
| if (is_kernel_core_data(addr)) |
| return 1; |
| |
| /* |
| * keys are allowed in the __ro_after_init section. |
| */ |
| if (is_kernel_rodata(addr)) |
| return 1; |
| |
| /* |
| * in initdata section and used during bootup only? |
| * NOTE: On some platforms the initdata section is |
| * outside of the _stext ... _end range. |
| */ |
| if (system_state < SYSTEM_FREEING_INITMEM && |
| init_section_contains((void *)addr, 1)) |
| 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 noinstr 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)) { |
| instrumentation_begin(); |
| 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(); |
| instrumentation_end(); |
| 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_notrace(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_ONCE(class->name != lock->name && |
| lock->key != &__lockdep_no_validate__, |
| "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n", |
| lock->name, lock->key, class->name); |
| 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, or maybe\n"); |
| pr_err("you didn't initialize this object before use?\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; |
| int idx; |
| |
| 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); |
| idx = class - lock_classes; |
| if (idx > max_lock_class_idx) |
| max_lock_class_idx = idx; |
| |
| 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, |
| 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 (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS) |
| #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 dependencies 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 redundant. |
| * |
| * 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); |
| } |
| |
| /* |
| * Dependency path printing: |
| * |
| * After BFS we get a lock dependency path (linked via ->parent of lock_list), |
| * printing out each lock in the dependency path will help on understanding how |
| * the deadlock could happen. Here are some details about dependency path |
| * printing: |
| * |
| * 1) A lock_list can be either forwards or backwards for a lock dependency, |
| * for a lock dependency A -> B, there are two lock_lists: |
| * |
| * a) lock_list in the ->locks_after list of A, whose ->class is B and |
| * ->links_to is A. In this case, we can say the lock_list is |
| * "A -> B" (forwards case). |
| * |
| * b) lock_list in the ->locks_before list of B, whose ->class is A |
| * and ->links_to is B. In this case, we can say the lock_list is |
| * "B <- A" (bacwards case). |
| * |
| * The ->trace of both a) and b) point to the call trace where B was |
| * acquired with A held. |
| * |
| * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't |
| * represent a certain lock dependency, it only provides an initial entry |
| * for BFS. For example, BFS may introduce a "helper" lock_list whose |
| * ->class is A, as a result BFS will search all dependencies starting with |
| * A, e.g. A -> B or A -> C. |
| * |
| * The notation of a forwards helper lock_list is like "-> A", which means |
| * we should search the forwards dependencies starting with "A", e.g A -> B |
| * or A -> C. |
| * |
| * The notation of a bacwards helper lock_list is like "<- B", which means |
| * we should search the backwards dependencies ending with "B", e.g. |
| * B <- A or B <- C. |
| */ |
| |
| /* |
| * printk the shortest lock dependencies from @root to @leaf in reverse order. |
| * |
| * We have a lock dependency path as follow: |
| * |
| * @root @leaf |
| * | | |
| * V V |
| * ->parent ->parent |
| * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list | |
| * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln| |
| * |
| * , so it's natural that we start from @leaf and print every ->class and |
| * ->trace until we reach the @root. |
| */ |
| 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)); |
| } |
| |
| /* |
| * printk the shortest lock dependencies from @leaf to @root. |
| * |
| * We have a lock dependency path (from a backwards search) as follow: |
| * |
| * @leaf @root |
| * | | |
| * V V |
| * ->parent ->parent |
| * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list | |
| * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln | |
| * |
| * , so when we iterate from @leaf to @root, we actually print the lock |
| * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order. |
| * |
| * Another thing to notice here is that ->class of L2 <- L1 is L1, while the |
| * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call |
| * trace of L1 in the dependency path, which is alright, because most of the |
| * time we can figure out where L1 is held from the call trace of L2. |
| */ |
| static void __used |
| print_shortest_lock_dependencies_backwards(struct lock_list *leaf, |
| struct lock_list *root) |
| { |
| struct lock_list *entry = leaf; |
| const struct lock_trace *trace = NULL; |
| int depth; |
| |
| /*compute depth from generated tree by BFS*/ |
| depth = get_lock_depth(leaf); |
| |
| do { |
| print_lock_class_header(entry->class, depth); |
| if (trace) { |
| printk("%*s ... acquired at:\n", depth, ""); |
| print_lock_trace(trace, 2); |
| printk("\n"); |
| } |
| |
| /* |
| * Record the pointer to the trace for the next lock_list |
| * entry, see the comments for the function. |
| */ |
| trace = entry->trace; |
| |
| 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); |
| print_shortest_lock_dependencies_backwards(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. |
| * |
| * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering |
| * the follow case: |
| * |
| * When trying to add A -> B to the graph, we find that there is a |
| * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M, |
| * that B -> ... -> M. However M is **softirq-safe**, if we use exact |
| * invert bits of M's usage_mask, we will find another lock N that is |
| * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not |
| * cause a inversion deadlock. |
| */ |
| backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL); |
| |
| 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_RNOMATCH 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. |
| * |
| * If we fail to return, we have inconsistency, i.e. |
| * <prev>::locks_after contains <next> while |
| * <next>::locks_before doesn't contain <prev>. In |
| * that case, we return after the inner and indicate |
| * something is wrong. |
| */ |
| list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) { |
| if (entry->class == hlock_class(prev)) { |
| if (distance == 1) |
| entry->distance = 1; |
| entry->dep |= calc_depb(prev, next); |
| return 1; |
| } |
| } |
| |
| /* <prev> is not found in <next>::locks_before */ |
| return 0; |
| } |
| } |
| |
| /* |
| * Is the <prev> -> <next> link redundant? |
| */ |
| ret = check_redundant(prev, next); |
| if (bfs_error(ret)) |
| return 0; |
| else if (ret == BFS_RMATCH) |
| return 2; |
| |
| if (!*trace) { |
| *trace = save_trace(); |
| if (!*trace) |
| return 0; |
| } |
| |
| /* |
| * Ok, all validations passed, add the new lock |
| * to the previous lock's dependency list: |
| */ |
| ret = add_lock_to_list(hlock_class(next), hlock_class(prev), |
| &hlock_class(prev)->locks_after, distance, |
| calc_dep(prev, next), *trace); |
| |
| if (!ret) |
| return 0; |
| |
| ret = add_lock_to_list(hlock_class(prev), hlock_class(next), |
| &hlock_class(next)->locks_before, distance, |
| calc_depb(prev, next), *trace); |
| if (!ret) |
| return 0; |
| |
| return 2; |
| } |
| |
| /* |
| * 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) |
| { |
| struct lock_trace *trace = NULL; |
| 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 (;;) { |
| u16 distance = curr->lockdep_depth - depth + 1; |
| hlock = curr->held_locks + depth - 1; |
| |
| if (hlock->check) { |
| int ret = check_prev_add(curr, hlock, next, distance, &trace); |
| if (!ret) |
| return 0; |
| |
| /* |
| * Stop after the first non-trylock entry, |
| * as non-trylock entries have added their |
| * own direct dependencies already, so this |
| * lock is connected to them indirectly: |
| */ |
| if (!hlock->trylock) |
| break; |
| } |
| |
| depth--; |
| /* |
| * End of lock-stack? |
| */ |
| if (!depth) |
| break; |
| /* |
| * Stop the search if we cross into another context: |
| */ |
| if (curr->held_locks[depth].irq_context != |
| curr->held_locks[depth-1].irq_context) |
| break; |
| } |
| return 1; |
| out_bug: |
| if (!debug_locks_off_graph_unlock()) |
| return 0; |
| |
| /* |
| * Clearly we all shouldn't be here, but since we made it we |
| * can reliable say we messed up our state. See the above two |
| * gotos for reasons why we could possibly end up here. |
| */ |
| WARN_ON(1); |
| |
| return 0; |
| } |
| |
| struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS]; |
| static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS); |
| static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS]; |
| unsigned long nr_zapped_lock_chains; |
| unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */ |
| unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */ |
| unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */ |
| |
| /* |
| * The first 2 chain_hlocks entries in the chain block in the bucket |
| * list contains the following meta data: |
| * |
| * entry[0]: |
| * Bit 15 - always set to 1 (it is not a class index) |
| * Bits 0-14 - upper 15 bits of the next block index |
| * entry[1] - lower 16 bits of next block index |
| * |
| * A next block index of all 1 bits means it is the end of the list. |
| * |
| * On the unsized bucket (bucket-0), the 3rd and 4th entries contain |
| * the chain block size: |
| * |
| * entry[2] - upper 16 bits of the chain block size |
| * entry[3] - lower 16 bits of the chain block size |
| */ |
| #define MAX_CHAIN_BUCKETS 16 |
| #define CHAIN_BLK_FLAG (1U << 15) |
| #define CHAIN_BLK_LIST_END 0xFFFFU |
| |
| static int chain_block_buckets[MAX_CHAIN_BUCKETS]; |
| |
| static inline int size_to_bucket(int size) |
| { |
| if (size > MAX_CHAIN_BUCKETS) |
| return 0; |
| |
| return size - 1; |
| } |
| |
| /* |
| * Iterate all the chain blocks in a bucket. |
| */ |
| #define for_each_chain_block(bucket, prev, curr) \ |
| for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \ |
| (curr) >= 0; \ |
| (prev) = (curr), (curr) = chain_block_next(curr)) |
| |
| /* |
| * next block or -1 |
| */ |
| static inline int chain_block_next(int offset) |
| { |
| int next = chain_hlocks[offset]; |
| |
| WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG)); |
| |
| if (next == CHAIN_BLK_LIST_END) |
| return -1; |
| |
| next &= ~CHAIN_BLK_FLAG; |
| next <<= 16; |
| next |= chain_hlocks[offset + 1]; |
| |
| return next; |
| } |
| |
| /* |
| * bucket-0 only |
| */ |
| static inline int chain_block_size(int offset) |
| { |
| return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3]; |
| } |
| |
| static inline void init_chain_block(int offset, int next, int bucket, int size) |
| { |
| chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG; |
| chain_hlocks[offset + 1] = (u16)next; |
| |
| if (size && !bucket) { |
| chain_hlocks[offset + 2] = size >> 16; |
| chain_hlocks[offset + 3] = (u16)size; |
| } |
| } |
| |
| static inline void add_chain_block(int offset, int size) |
| { |
| int bucket = size_to_bucket(size); |
| int next = chain_block_buckets[bucket]; |
|