diff options
Diffstat (limited to 'kernel/lockdep.c')
| -rw-r--r-- | kernel/lockdep.c | 248 |
1 files changed, 201 insertions, 47 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 8c24294e477f..e69434b070da 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -96,8 +96,13 @@ static int graph_lock(void) static inline int graph_unlock(void) { - if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) + if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) { + /* + * The lockdep graph lock isn't locked while we expect it to + * be, we're confused now, bye! + */ return DEBUG_LOCKS_WARN_ON(1); + } current->lockdep_recursion--; arch_spin_unlock(&lockdep_lock); @@ -134,6 +139,9 @@ static struct lock_class lock_classes[MAX_LOCKDEP_KEYS]; static inline struct lock_class *hlock_class(struct held_lock *hlock) { if (!hlock->class_idx) { + /* + * Someone passed in garbage, we give up. + */ DEBUG_LOCKS_WARN_ON(1); return NULL; } @@ -687,6 +695,10 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass) */ list_for_each_entry(class, hash_head, hash_entry) { if (class->key == key) { + /* + * Huh! same key, different name? Did someone trample + * on some memory? We're most confused. + */ WARN_ON_ONCE(class->name != lock->name); return class; } @@ -800,6 +812,10 @@ out_unlock_set: 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; @@ -926,7 +942,7 @@ static inline void mark_lock_accessed(struct lock_list *lock, unsigned long nr; nr = lock - list_entries; - WARN_ON(nr >= nr_list_entries); + WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */ lock->parent = parent; lock->class->dep_gen_id = lockdep_dependency_gen_id; } @@ -936,7 +952,7 @@ static inline unsigned long lock_accessed(struct lock_list *lock) unsigned long nr; nr = lock - list_entries; - WARN_ON(nr >= nr_list_entries); + WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */ return lock->class->dep_gen_id == lockdep_dependency_gen_id; } @@ -1129,10 +1145,11 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth, if (debug_locks_silent) return 0; - printk("\n=======================================================\n"); - printk( "[ INFO: possible circular locking dependency detected ]\n"); + printk("\n"); + printk("======================================================\n"); + printk("[ INFO: possible circular locking dependency detected ]\n"); print_kernel_version(); - printk( "-------------------------------------------------------\n"); + printk("-------------------------------------------------------\n"); printk("%s/%d is trying to acquire lock:\n", curr->comm, task_pid_nr(curr)); print_lock(check_src); @@ -1196,6 +1213,9 @@ static noinline int print_bfs_bug(int ret) if (!debug_locks_off_graph_unlock()) return 0; + /* + * Breadth-first-search failed, graph got corrupted? + */ WARN(1, "lockdep bfs error:%d\n", ret); return 0; @@ -1463,11 +1483,12 @@ print_bad_irq_dependency(struct task_struct *curr, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return 0; - printk("\n======================================================\n"); - printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n", + printk("\n"); + printk("======================================================\n"); + printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n", irqclass, irqclass); print_kernel_version(); - printk( "------------------------------------------------------\n"); + printk("------------------------------------------------------\n"); printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n", curr->comm, task_pid_nr(curr), curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT, @@ -1692,10 +1713,11 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return 0; - printk("\n=============================================\n"); - printk( "[ INFO: possible recursive locking detected ]\n"); + printk("\n"); + printk("=============================================\n"); + printk("[ INFO: possible recursive locking detected ]\n"); print_kernel_version(); - printk( "---------------------------------------------\n"); + printk("---------------------------------------------\n"); printk("%s/%d is trying to acquire lock:\n", curr->comm, task_pid_nr(curr)); print_lock(next); @@ -1944,6 +1966,11 @@ 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; @@ -1975,6 +2002,11 @@ static inline int lookup_chain_cache(struct task_struct *curr, struct held_lock *hlock_curr, *hlock_next; int i, j; + /* + * We might need to take the graph lock, ensure we've got IRQs + * disabled to make this an IRQ-safe lock.. for recursion reasons + * lockdep won't complain about its own locking errors. + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return 0; /* @@ -2126,6 +2158,10 @@ static void check_chain_key(struct task_struct *curr) hlock = curr->held_locks + i; if (chain_key != hlock->prev_chain_key) { debug_locks_off(); + /* + * We got mighty confused, our chain keys don't match + * with what we expect, someone trample on our task state? + */ WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n", curr->lockdep_depth, i, (unsigned long long)chain_key, @@ -2133,6 +2169,9 @@ static void check_chain_key(struct task_struct *curr) return; } id = hlock->class_idx - 1; + /* + * Whoops ran out of static storage again? + */ if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)) return; @@ -2144,6 +2183,10 @@ static void check_chain_key(struct task_struct *curr) } if (chain_key != curr->curr_chain_key) { debug_locks_off(); + /* + * More smoking hash instead of calculating it, damn see these + * numbers float.. I bet that a pink elephant stepped on my memory. + */ WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n", curr->lockdep_depth, i, (unsigned long long)chain_key, @@ -2177,10 +2220,11 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return 0; - printk("\n=================================\n"); - printk( "[ INFO: inconsistent lock state ]\n"); + printk("\n"); + printk("=================================\n"); + printk("[ INFO: inconsistent lock state ]\n"); print_kernel_version(); - printk( "---------------------------------\n"); + printk("---------------------------------\n"); printk("inconsistent {%s} -> {%s} usage.\n", usage_str[prev_bit], usage_str[new_bit]); @@ -2241,10 +2285,11 @@ print_irq_inversion_bug(struct task_struct *curr, if (!debug_locks_off_graph_unlock() || debug_locks_silent) return 0; - printk("\n=========================================================\n"); - printk( "[ INFO: possible irq lock inversion dependency detected ]\n"); + printk("\n"); + printk("=========================================================\n"); + printk("[ INFO: possible irq lock inversion dependency detected ]\n"); print_kernel_version(); - printk( "---------------------------------------------------------\n"); + printk("---------------------------------------------------------\n"); printk("%s/%d just changed the state of lock:\n", curr->comm, task_pid_nr(curr)); print_lock(this); @@ -2525,12 +2570,24 @@ void trace_hardirqs_on_caller(unsigned long ip) return; } + /* + * We're enabling irqs and according to our state above irqs weren't + * already enabled, yet we find the hardware thinks they are in fact + * enabled.. someone messed up their IRQ state tracing. + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return; + /* + * See the fine text that goes along with this variable definition. + */ if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled))) return; + /* + * Can't allow enabling interrupts while in an interrupt handler, + * that's general bad form and such. Recursion, limited stack etc.. + */ if (DEBUG_LOCKS_WARN_ON(current->hardirq_context)) return; @@ -2558,6 +2615,10 @@ void trace_hardirqs_off_caller(unsigned long ip) if (unlikely(!debug_locks || current->lockdep_recursion)) return; + /* + * So we're supposed to get called after you mask local IRQs, but for + * some reason the hardware doesn't quite think you did a proper job. + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return; @@ -2590,6 +2651,10 @@ void trace_softirqs_on(unsigned long ip) if (unlikely(!debug_locks || current->lockdep_recursion)) return; + /* + * We fancy IRQs being disabled here, see softirq.c, avoids + * funny state and nesting things. + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return; @@ -2626,6 +2691,9 @@ void trace_softirqs_off(unsigned long ip) if (unlikely(!debug_locks || current->lockdep_recursion)) return; + /* + * We fancy IRQs being disabled here, see softirq.c + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return; @@ -2637,6 +2705,9 @@ void trace_softirqs_off(unsigned long ip) curr->softirq_disable_ip = ip; curr->softirq_disable_event = ++curr->irq_events; debug_atomic_inc(softirqs_off_events); + /* + * Whoops, we wanted softirqs off, so why aren't they? + */ DEBUG_LOCKS_WARN_ON(!softirq_count()); } else debug_atomic_inc(redundant_softirqs_off); @@ -2661,6 +2732,9 @@ static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags) if (!(gfp_mask & __GFP_FS)) return; + /* + * Oi! Can't be having __GFP_FS allocations with IRQs disabled. + */ if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))) return; @@ -2773,13 +2847,13 @@ static int separate_irq_context(struct task_struct *curr, return 0; } -#else +#else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */ static inline int mark_lock_irq(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit new_bit) { - WARN_ON(1); + WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */ return 1; } @@ -2799,7 +2873,7 @@ void lockdep_trace_alloc(gfp_t gfp_mask) { } -#endif +#endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */ /* * Mark a lock with a usage bit, and validate the state transition: @@ -2880,6 +2954,9 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name, lock->cpu = raw_smp_processor_id(); #endif + /* + * Can't be having no nameless bastards around this place! + */ if (DEBUG_LOCKS_WARN_ON(!name)) { lock->name = "NULL"; return; @@ -2887,6 +2964,9 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name, lock->name = name; + /* + * No key, no joy, we need to hash something. + */ if (DEBUG_LOCKS_WARN_ON(!key)) return; /* @@ -2894,6 +2974,9 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name, */ if (!static_obj(key)) { printk("BUG: key %p not in .data!\n", key); + /* + * What it says above ^^^^^, I suggest you read it. + */ DEBUG_LOCKS_WARN_ON(1); return; } @@ -2932,6 +3015,11 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, if (unlikely(!debug_locks)) return 0; + /* + * Lockdep should run with IRQs disabled, otherwise we could + * get an interrupt which would want to take locks, which would + * end up in lockdep and have you got a head-ache already? + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return 0; @@ -2963,6 +3051,9 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, * dependency checks are done) */ depth = curr->lockdep_depth; + /* + * Ran out of static storage for our per-task lock stack again have we? + */ if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH)) return 0; @@ -2981,6 +3072,10 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, } hlock = curr->held_locks + depth; + /* + * Plain impossible, we just registered it and checked it weren't no + * NULL like.. I bet this mushroom I ate was good! + */ if (DEBUG_LOCKS_WARN_ON(!class)) return 0; hlock->class_idx = class_idx; @@ -3015,11 +3110,17 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, * the hash, not class->key. */ id = class - lock_classes; + /* + * Whoops, we did it again.. ran straight out of our static allocation. + */ if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)) return 0; chain_key = curr->curr_chain_key; if (!depth) { + /* + * How can we have a chain hash when we ain't got no keys?! + */ if (DEBUG_LOCKS_WARN_ON(chain_key != 0)) return 0; chain_head = 1; @@ -3065,9 +3166,10 @@ print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock, if (debug_locks_silent) return 0; - printk("\n=====================================\n"); - printk( "[ BUG: bad unlock balance detected! ]\n"); - printk( "-------------------------------------\n"); + printk("\n"); + printk("=====================================\n"); + printk("[ BUG: bad unlock balance detected! ]\n"); + printk("-------------------------------------\n"); printk("%s/%d is trying to release lock (", curr->comm, task_pid_nr(curr)); print_lockdep_cache(lock); @@ -3091,6 +3193,9 @@ static int check_unlock(struct task_struct *curr, struct lockdep_map *lock, { if (unlikely(!debug_locks)) return 0; + /* + * Lockdep should run with IRQs disabled, recursion, head-ache, etc.. + */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return 0; @@ -3111,9 +3216,20 @@ static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock) if (!class) class = look_up_lock_class(lock, 0); - if (DEBUG_LOCKS_WARN_ON(!class)) + /* + * If look_up_lock_class() failed to find a class, we're trying + * to test if we hold a lock that has never yet been acquired. + * Clearly if the lock hasn't been acquired _ever_, we're not + * holding it either, so report failure. + */ + if (!class) return 0; + /* + * References, but not a lock we're actually ref-counting? + * State got messed up, follow the sites that change ->references + * and try to make sense of it. + */ if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock)) return 0; @@ -3136,6 +3252,10 @@ __lock_set_class(struct lockdep_map *lock, const char *name, int i; depth = curr->lockdep_depth; + /* + * This function is about (re)setting the class of a held lock, + * yet we're not actually holding any locks. Naughty user! + */ if (DEBUG_LOCKS_WARN_ON(!depth)) return 0; @@ -3171,6 +3291,10 @@ found_it: return 0; } + /* + * I took it apart and put it back together again, except now I have + * these 'spare' parts.. where shall I put them. + */ if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth)) return 0; return 1; @@ -3195,6 +3319,10 @@ lock_release_non_nested(struct task_struct *curr, * of held locks: */ depth = curr->lockdep_depth; + /* + * So we're all set to release this lock.. wait what lock? We don't + * own any locks, you've been drinking again? + */ if (DEBUG_LOCKS_WARN_ON(!depth)) return 0; @@ -3247,6 +3375,10 @@ found_it: return 0; } + /* + * We had N bottles of beer on the wall, we drank one, but now + * there's not N-1 bottles of beer left on the wall... + */ if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1)) return 0; return 1; @@ -3277,6 +3409,9 @@ static int lock_release_nested(struct task_struct *curr, return lock_release_non_nested(curr, lock, ip); curr->lockdep_depth--; + /* + * No more locks, but somehow we've got hash left over, who left it? + */ if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0))) return 0; @@ -3359,10 +3494,13 @@ static void check_flags(unsigned long flags) * check if not in hardirq contexts: */ if (!hardirq_count()) { - if (softirq_count()) + if (softirq_count()) { + /* like the above, but with softirqs */ DEBUG_LOCKS_WARN_ON(current->softirqs_enabled); - else + } else { + /* lick the above, does it taste good? */ DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled); + } } if (!debug_locks) @@ -3472,9 +3610,10 @@ print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock, if (debug_locks_silent) return 0; - printk("\n=================================\n"); - printk( "[ BUG: bad contention detected! ]\n"); - printk( "---------------------------------\n"); + printk("\n"); + printk("=================================\n"); + printk("[ BUG: bad contention detected! ]\n"); + printk("---------------------------------\n"); printk("%s/%d is trying to contend lock (", curr->comm, task_pid_nr(curr)); print_lockdep_cache(lock); @@ -3500,6 +3639,10 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip) int i, contention_point, contending_point; depth = curr->lockdep_depth; + /* + * Whee, we contended on this lock, except it seems we're not + * actually trying to acquire anything much at all.. + */ if (DEBUG_LOCKS_WARN_ON(!depth)) return; @@ -3549,6 +3692,10 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip) int i, cpu; depth = curr->lockdep_depth; + /* + * Yay, we acquired ownership of this lock we didn't try to + * acquire, how the heck did that happen? + */ if (DEBUG_LOCKS_WARN_ON(!depth)) return; @@ -3753,8 +3900,12 @@ void lockdep_reset_lock(struct lockdep_map *lock) match |= class == lock->class_cache[j]; if (unlikely(match)) { - if (debug_locks_off_graph_unlock()) + if (debug_locks_off_graph_unlock()) { + /* + * We all just reset everything, how did it match? + */ WARN_ON(1); + } goto out_restore; } } @@ -3833,9 +3984,10 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from, if (debug_locks_silent) return; - printk("\n=========================\n"); - printk( "[ BUG: held lock freed! ]\n"); - printk( "-------------------------\n"); + printk("\n"); + printk("=========================\n"); + printk("[ BUG: held lock freed! ]\n"); + printk("-------------------------\n"); printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n", curr->comm, task_pid_nr(curr), mem_from, mem_to-1); print_lock(hlock); @@ -3889,9 +4041,10 @@ static void print_held_locks_bug(struct task_struct *curr) if (debug_locks_silent) return; - printk("\n=====================================\n"); - printk( "[ BUG: lock held at task exit time! ]\n"); - printk( "-------------------------------------\n"); + printk("\n"); + printk("=====================================\n"); + printk("[ BUG: lock held at task exit time! ]\n"); + printk("-------------------------------------\n"); printk("%s/%d is exiting with locks still held!\n", curr->comm, task_pid_nr(curr)); lockdep_print_held_locks(curr); @@ -3985,16 +4138,17 @@ void lockdep_sys_exit(void) if (unlikely(curr->lockdep_depth)) { if (!debug_locks_off()) return; - printk("\n================================================\n"); - printk( "[ BUG: lock held when returning to user space! ]\n"); - printk( "------------------------------------------------\n"); + printk("\n"); + printk("================================================\n"); + printk("[ BUG: lock held when returning to user space! ]\n"); + printk("------------------------------------------------\n"); printk("%s/%d is leaving the kernel with locks still held!\n", curr->comm, curr->pid); lockdep_print_held_locks(curr); } } -void lockdep_rcu_dereference(const char *file, const int line) +void lockdep_rcu_suspicious(const char *file, const int line, const char *s) { struct task_struct *curr = current; @@ -4003,15 +4157,15 @@ void lockdep_rcu_dereference(const char *file, const int line) return; #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */ /* Note: the following can be executed concurrently, so be careful. */ - printk("\n===================================================\n"); - printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n"); - printk( "---------------------------------------------------\n"); - printk("%s:%d invoked rcu_dereference_check() without protection!\n", - file, line); + printk("\n"); + printk("===============================\n"); + printk("[ INFO: suspicious RCU usage. ]\n"); + printk("-------------------------------\n"); + printk("%s:%d %s!\n", file, line, s); printk("\nother info that might help us debug this:\n\n"); printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks); lockdep_print_held_locks(curr); printk("\nstack backtrace:\n"); dump_stack(); } -EXPORT_SYMBOL_GPL(lockdep_rcu_dereference); +EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious); |