Count lock contention events per lock class. Additionally track the first four callsites that resulted in the contention. /proc/lock_contentions - gives a single line per lock class: <(write) contentions> Followed by another three columns per contention point: writing a '0' to the file will clear the stats. example output: [root@taijtu ~]# cat /proc/lock_contentions | sort -rnk 2 | head dcache_lock: 3000 0 [618] [] _atomic_dec_and_lock+0x39/0x58 [17] [] sysfs_open_file+0x28/0x25a [160] [] d_instantiate+0x2a/0xad [52] [] __link_path_walk+0x270/0xde9 &inode->i_mutex: 235 0 [15] [] pipe_read+0x74/0x39d [23] [] pipe_wait+0x86/0x8d [105] [] do_lookup+0x81/0x1ae [85] [] vfs_readdir+0x5c/0xa9 &zone->lru_lock: 141 0 [11] [] activate_page+0x37/0xd6 [75] [] release_pages+0xb2/0x16c [42] [] __pagevec_lru_add_active+0x62/0xe5 [12] [] __pagevec_lru_add+0x63/0xe2 &rq->rq_lock_key: 93 0 [66] [] task_rq_lock+0x42/0x74 [24] [] __sched_text_start+0x17a/0x869 [2] [] double_rq_lock+0x38/0x3d [1] [] double_lock_balance+0x41/0x52 &rq->rq_lock_key: 59 0 [15] [] __sched_text_start+0x17a/0x869 [27] [] task_rq_lock+0x42/0x74 [17] [] __sched_text_start+0x2e0/0x869 files_lock: 57 0 [28] [] file_move+0x1d/0x51 [29] [] file_kill+0x15/0x39 &inode->i_data.i_mmap_lock: 52 0 [16] [] copy_process+0xe10/0x1684 [5] [] vma_link+0x40/0x107 [20] [] unlink_file_vma+0x2c/0x53 [11] [] vma_adjust+0x154/0x452 &q->__queue_lock: 47 0 [16] [] __make_request+0x5e/0x663 [4] [] __make_request+0x5bc/0x663 [2] [] generic_unplug_device+0x18/0x25 [1] [] generic_unplug_device+0x10/0x25 &dentry->d_lock: 26 0 [22] [] __d_lookup+0x7d/0x136 [4] [] dnotify_parent+0x1f/0x6d vfsmount_lock: 17 0 [16] [] lookup_mnt+0x19/0x4c [1] [] __d_path+0xae/0x14c Signed-off-by: Peter Zijlstra --- include/linux/lockdep.h | 33 ++++++++++++++++ kernel/lockdep.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++ kernel/lockdep_proc.c | 79 +++++++++++++++++++++++++++++++++++++++ kernel/mutex.c | 7 +++ kernel/rwsem.c | 8 ++-- kernel/spinlock.c | 28 +++++++------- lib/Kconfig.debug | 13 ++++++ 7 files changed, 245 insertions(+), 18 deletions(-) Index: linux-2.6/include/linux/lockdep.h =================================================================== --- linux-2.6.orig/include/linux/lockdep.h 2007-05-22 23:29:08.000000000 +0200 +++ linux-2.6/include/linux/lockdep.h 2007-05-22 23:46:47.000000000 +0200 @@ -16,6 +16,7 @@ struct task_struct; #include #include #include +#include /* * Lock-class usage-state bits: @@ -71,6 +72,11 @@ struct lock_class_key { struct lockdep_subclass_key subkeys[MAX_LOCKDEP_SUBCLASSES]; }; +struct lock_contention_point { + unsigned long ip; + atomic_t count; +}; + /* * The lock-class itself: */ @@ -114,6 +120,12 @@ struct lock_class { const char *name; int name_version; + +#ifdef CONFIG_LOCK_STAT + atomic_t read_contentions; + atomic_t write_contentions; + struct lock_contention_point contention_point[4]; +#endif }; /* @@ -281,6 +293,27 @@ struct lock_class_key { }; #endif /* !LOCKDEP */ +#ifdef CONFIG_LOCK_STAT + +extern void lock_contended(struct lockdep_map *lock, unsigned long ip); + +#define LOCK_CONTENDED(_lock, try, lock) \ +do { \ + if (!try(_lock)) { \ + lock_contended(&(_lock)->dep_map, _RET_IP_); \ + lock(_lock); \ + } \ +} while (0) + +#else /* CONFIG_LOCK_STAT */ + +#define lock_contended(l, i) do { } while (0) + +#define LOCK_CONTENDED(_lock, try, lock) \ + lock(_lock) + +#endif /* CONFIG_LOCK_STAT */ + #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_GENERIC_HARDIRQS) extern void early_init_irq_lock_class(void); #else Index: linux-2.6/kernel/lockdep.c =================================================================== --- linux-2.6.orig/kernel/lockdep.c 2007-05-22 23:46:23.000000000 +0200 +++ linux-2.6/kernel/lockdep.c 2007-05-22 23:46:47.000000000 +0200 @@ -2274,6 +2274,35 @@ print_unlock_inbalance_bug(struct task_s return 0; } +#ifdef CONFIG_LOCK_STAT +static int +print_lock_contention_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 contention detected! ]\n"); + printk( "---------------------------------\n"); + printk("%s/%d is trying to contend lock (", + curr->comm, curr->pid); + print_lockdep_cache(lock); + printk(") at:\n"); + print_ip_sym(ip); + printk("but there are no locks held!\n"); + printk("\nother info that might help us debug this:\n"); + lockdep_print_held_locks(curr); + + printk("\nstack backtrace:\n"); + dump_stack(); + + return 0; +} +#endif + /* * Common debugging checks for both nested and non-nested unlock: */ @@ -2414,6 +2443,54 @@ __lock_release(struct lockdep_map *lock, check_chain_key(curr); } +#ifdef CONFIG_LOCK_STAT +static void +__lock_contended(struct lockdep_map *lock, unsigned long ip) +{ + struct task_struct *curr = current; + struct held_lock *hlock, *prev_hlock; + unsigned int depth; + int i; + + depth = curr->lockdep_depth; + if (DEBUG_LOCKS_WARN_ON(!depth)) + return; + + 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; + } + print_lock_contention_bug(curr, lock, ip); + return; + +found_it: + if (hlock->read) + atomic_inc(&hlock->class->read_contentions); + else + atomic_inc(&hlock->class->write_contentions); + + for (i = 0; i < ARRAY_SIZE(hlock->class->contention_point); i++) { + if (hlock->class->contention_point[i].ip == 0) { + hlock->class->contention_point[i].ip = ip; + atomic_set(&hlock->class->contention_point[i].count, 1); + break; + } + if (hlock->class->contention_point[i].ip == ip) { + atomic_inc(&hlock->class->contention_point[i].count); + break; + } + } +} +#endif + /* * Check whether we follow the irq-flags state precisely: */ @@ -2486,6 +2563,24 @@ void lock_release(struct lockdep_map *lo EXPORT_SYMBOL_GPL(lock_release); +#ifdef CONFIG_LOCK_STAT +void lock_contended(struct lockdep_map *lock, 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_contended(lock, ip); + current->lockdep_recursion = 0; + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_contended); +#endif + /* * Used by the testsuite, sanitize the validator state * after a simulated failure: Index: linux-2.6/kernel/mutex.c =================================================================== --- linux-2.6.orig/kernel/mutex.c 2007-05-22 23:29:08.000000000 +0200 +++ linux-2.6/kernel/mutex.c 2007-05-22 23:46:47.000000000 +0200 @@ -139,6 +139,12 @@ __mutex_lock_common(struct mutex *lock, list_add_tail(&waiter.list, &lock->wait_list); waiter.task = task; + old_val = atomic_xchg(&lock->count, -1); + if (old_val == 1) + goto done; + + lock_contended(&lock->dep_map, _RET_IP_); + for (;;) { /* * Lets try to take the lock again - this is needed even if @@ -174,6 +180,7 @@ __mutex_lock_common(struct mutex *lock, spin_lock_mutex(&lock->wait_lock, flags); } +done: /* got the lock - rejoice! */ mutex_remove_waiter(lock, &waiter, task_thread_info(task)); debug_mutex_set_owner(lock, task_thread_info(task)); Index: linux-2.6/kernel/lockdep_proc.c =================================================================== --- linux-2.6.orig/kernel/lockdep_proc.c 2007-05-22 23:29:08.000000000 +0200 +++ linux-2.6/kernel/lockdep_proc.c 2007-05-22 23:46:47.000000000 +0200 @@ -15,6 +15,7 @@ #include #include #include +#include #include "lockdep_internals.h" @@ -342,6 +343,78 @@ static const struct file_operations proc .release = seq_release, }; +#ifdef CONFIG_LOCK_STAT +static int lock_contentions_show(struct seq_file *m, void *v) +{ + struct lock_contention_point *cp; + char sym[KSYM_SYMBOL_LEN]; + struct lock_class *class; + int r, w, i; + + list_for_each_entry(class, &all_lock_classes, lock_entry) { + r = atomic_read(&class->read_contentions); + w = atomic_read(&class->write_contentions); + + if (r || w) { + seq_printf(m, "%s: %d %d", class->name, w, r); + for (i = 0; i < ARRAY_SIZE(class->contention_point); + i++) { + cp = &class->contention_point[i]; + + if (cp->ip == 0) + break; + sprint_symbol(sym, cp->ip); + seq_printf(m, " [%d] [<%p>] %s", + atomic_read(&cp->count), + (void *)cp->ip, sym); + } + seq_printf(m, "\n"); + } + } + + return 0; +} + +static int lock_contentions_open(struct inode *inode, struct file *file) +{ + return single_open(file, lock_contentions_show, NULL); +} + +ssize_t lock_contentions_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct lock_class *class; + char c; + int i; + + if (count) { + if (get_user(c, buf)) + return -EFAULT; + + if (c != '0') + return count; + + list_for_each_entry(class, &all_lock_classes, lock_entry) { + atomic_set(&class->write_contentions, 0); + atomic_set(&class->read_contentions, 0); + for (i = 0; i < ARRAY_SIZE(class->contention_point); + i++) { + class->contention_point[i].ip = 0; + } + } + } + return count; +} + +static const struct file_operations proc_lock_contentions_operations = { + .open = lock_contentions_open, + .write = lock_contentions_write, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; +#endif /* CONFIG_LOCK_STAT */ + static int __init lockdep_proc_init(void) { struct proc_dir_entry *entry; @@ -354,6 +427,12 @@ static int __init lockdep_proc_init(void if (entry) entry->proc_fops = &proc_lockdep_stats_operations; +#ifdef CONFIG_LOCK_STAT + entry = create_proc_entry("lock_contentions", S_IRUSR, NULL); + if (entry) + entry->proc_fops = &proc_lock_contentions_operations; +#endif + return 0; } Index: linux-2.6/kernel/rwsem.c =================================================================== --- linux-2.6.orig/kernel/rwsem.c 2007-05-22 23:29:08.000000000 +0200 +++ linux-2.6/kernel/rwsem.c 2007-05-22 23:46:47.000000000 +0200 @@ -20,7 +20,7 @@ void down_read(struct rw_semaphore *sem) might_sleep(); rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); - __down_read(sem); + LOCK_CONTENDED(sem, __down_read_trylock, __down_read); } EXPORT_SYMBOL(down_read); @@ -47,7 +47,7 @@ void down_write(struct rw_semaphore *sem might_sleep(); rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); - __down_write(sem); + LOCK_CONTENDED(sem, __down_write_trylock, __down_write); } EXPORT_SYMBOL(down_write); @@ -111,7 +111,7 @@ void down_read_nested(struct rw_semaphor might_sleep(); rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); - __down_read(sem); + LOCK_CONTENDED(sem, __down_read_trylock, __down_read); } EXPORT_SYMBOL(down_read_nested); @@ -130,7 +130,7 @@ void down_write_nested(struct rw_semapho might_sleep(); rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); - __down_write_nested(sem, subclass); + LOCK_CONTENDED(sem, __down_write_trylock, __down_write); } EXPORT_SYMBOL(down_write_nested); Index: linux-2.6/kernel/spinlock.c =================================================================== --- linux-2.6.orig/kernel/spinlock.c 2007-05-22 23:29:08.000000000 +0200 +++ linux-2.6/kernel/spinlock.c 2007-05-22 23:46:47.000000000 +0200 @@ -72,7 +72,7 @@ void __lockfunc _read_lock(rwlock_t *loc { preempt_disable(); rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_); - _raw_read_lock(lock); + LOCK_CONTENDED(lock, _raw_read_trylock, _raw_read_lock); } EXPORT_SYMBOL(_read_lock); @@ -89,7 +89,7 @@ unsigned long __lockfunc _spin_lock_irqs * that interrupts are not re-enabled during lock-acquire: */ #ifdef CONFIG_PROVE_LOCKING - _raw_spin_lock(lock); + LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock); #else _raw_spin_lock_flags(lock, &flags); #endif @@ -102,7 +102,7 @@ void __lockfunc _spin_lock_irq(spinlock_ local_irq_disable(); preempt_disable(); spin_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_spin_lock(lock); + LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock); } EXPORT_SYMBOL(_spin_lock_irq); @@ -111,7 +111,7 @@ void __lockfunc _spin_lock_bh(spinlock_t local_bh_disable(); preempt_disable(); spin_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_spin_lock(lock); + LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock); } EXPORT_SYMBOL(_spin_lock_bh); @@ -122,7 +122,7 @@ unsigned long __lockfunc _read_lock_irqs local_irq_save(flags); preempt_disable(); rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_); - _raw_read_lock(lock); + LOCK_CONTENDED(lock, _raw_read_trylock, _raw_read_lock); return flags; } EXPORT_SYMBOL(_read_lock_irqsave); @@ -132,7 +132,7 @@ void __lockfunc _read_lock_irq(rwlock_t local_irq_disable(); preempt_disable(); rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_); - _raw_read_lock(lock); + LOCK_CONTENDED(lock, _raw_read_trylock, _raw_read_lock); } EXPORT_SYMBOL(_read_lock_irq); @@ -141,7 +141,7 @@ void __lockfunc _read_lock_bh(rwlock_t * local_bh_disable(); preempt_disable(); rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_); - _raw_read_lock(lock); + LOCK_CONTENDED(lock, _raw_read_trylock, _raw_read_lock); } EXPORT_SYMBOL(_read_lock_bh); @@ -152,7 +152,7 @@ unsigned long __lockfunc _write_lock_irq local_irq_save(flags); preempt_disable(); rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_write_lock(lock); + LOCK_CONTENDED(lock, _raw_write_trylock, _raw_write_lock); return flags; } EXPORT_SYMBOL(_write_lock_irqsave); @@ -162,7 +162,7 @@ void __lockfunc _write_lock_irq(rwlock_t local_irq_disable(); preempt_disable(); rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_write_lock(lock); + LOCK_CONTENDED(lock, _raw_write_trylock, _raw_write_lock); } EXPORT_SYMBOL(_write_lock_irq); @@ -171,7 +171,7 @@ void __lockfunc _write_lock_bh(rwlock_t local_bh_disable(); preempt_disable(); rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_write_lock(lock); + LOCK_CONTENDED(lock, _raw_write_trylock, _raw_write_lock); } EXPORT_SYMBOL(_write_lock_bh); @@ -179,7 +179,7 @@ void __lockfunc _spin_lock(spinlock_t *l { preempt_disable(); spin_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_spin_lock(lock); + LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock); } EXPORT_SYMBOL(_spin_lock); @@ -188,7 +188,7 @@ void __lockfunc _write_lock(rwlock_t *lo { preempt_disable(); rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_); - _raw_write_lock(lock); + LOCK_CONTENDED(lock, _raw_write_trylock, _raw_write_lock); } EXPORT_SYMBOL(_write_lock); @@ -289,7 +289,7 @@ void __lockfunc _spin_lock_nested(spinlo { preempt_disable(); spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_); - _raw_spin_lock(lock); + LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock); } EXPORT_SYMBOL(_spin_lock_nested); @@ -306,7 +306,7 @@ unsigned long __lockfunc _spin_lock_irqs * that interrupts are not re-enabled during lock-acquire: */ #ifdef CONFIG_PROVE_SPIN_LOCKING - _raw_spin_lock(lock); + LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock); #else _raw_spin_lock_flags(lock, &flags); #endif Index: linux-2.6/lib/Kconfig.debug =================================================================== --- linux-2.6.orig/lib/Kconfig.debug 2007-05-22 23:29:08.000000000 +0200 +++ linux-2.6/lib/Kconfig.debug 2007-05-22 23:46:47.000000000 +0200 @@ -258,6 +258,17 @@ config LOCKDEP select KALLSYMS select KALLSYMS_ALL +config LOCK_STAT + bool "Lock usage statisitics" + depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT + select LOCKDEP + select DEBUG_SPINLOCK + select DEBUG_MUTEXES + select DEBUG_LOCK_ALLOC + default n + help + This feature enables tracking lock contention points + config DEBUG_LOCKDEP bool "Lock dependency engine debugging" depends on DEBUG_KERNEL && LOCKDEP @@ -442,3 +453,5 @@ config FAULT_INJECTION_STACKTRACE_FILTER select FRAME_POINTER help Provide stacktrace filter for fault-injection capabilities + + -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/