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