Add lock contention tracking to lockdep
[root@taijtu ~]# cat /proc/lockdep_contentions | sort -rnk 2 | head
dcache_lock: 3000 0 [618] [<ffffffff8033badd>] _atomic_dec_and_lock+0x39/0x58 [17] [<ffffffff802d6dce>] sysfs_open_file+0x28/0x25a [160] [<ffffffff802a5b61>] d_instantiate+0x2a/0xad [52] [<ffffffff8029d926>] __link_path_walk+0x270/0xde9
&inode->i_mutex: 235 0 [15] [<ffffffff8029b053>] pipe_read+0x74/0x39d [23] [<ffffffff8029a9f8>] pipe_wait+0x86/0x8d [105] [<ffffffff8029bc9a>] do_lookup+0x81/0x1ae [85] [<ffffffff802a0be7>] vfs_readdir+0x5c/0xa9
&zone->lru_lock: 141 0 [11] [<ffffffff8027366b>] activate_page+0x37/0xd6 [75] [<ffffffff80273327>] release_pages+0xb2/0x16c [42] [<ffffffff80273443>] __pagevec_lru_add_active+0x62/0xe5 [12] [<ffffffff80273529>] __pagevec_lru_add+0x63/0xe2
&rq->rq_lock_key: 93 0 [66] [<ffffffff8022b202>] task_rq_lock+0x42/0x74 [24] [<ffffffff80461f2a>] __sched_text_start+0x17a/0x869 [2] [<ffffffff8022a58e>] double_rq_lock+0x38/0x3d [1] [<ffffffff8022b1af>] double_lock_balance+0x41/0x52
&rq->rq_lock_key: 59 0 [15] [<ffffffff80461f2a>] __sched_text_start+0x17a/0x869 [27] [<ffffffff8022b202>] task_rq_lock+0x42/0x74 [17] [<ffffffff80462090>] __sched_text_start+0x2e0/0x869
files_lock: 57 0 [28] [<ffffffff8029581d>] file_move+0x1d/0x51 [29] [<ffffffff802957dc>] file_kill+0x15/0x39
&inode->i_data.i_mmap_lock: 52 0 [16] [<ffffffff8023149f>] copy_process+0xe10/0x1684 [5] [<ffffffff8027e38d>] vma_link+0x40/0x107 [20] [<ffffffff8027d866>] unlink_file_vma+0x2c/0x53 [11] [<ffffffff8027da53>] vma_adjust+0x154/0x452
&q->__queue_lock: 47 0 [16] [<ffffffff8033348a>] __make_request+0x5e/0x663 [4] [<ffffffff803339e8>] __make_request+0x5bc/0x663 [2] [<ffffffff803320c3>] generic_unplug_device+0x18/0x25 [1] [<ffffffff803320bb>] generic_unplug_device+0x10/0x25
&dentry->d_lock: 26 0 [22] [<ffffffff802a58be>] __d_lookup+0x7d/0x136 [4] [<ffffffff802ccd61>] dnotify_parent+0x1f/0x6d
vfsmount_lock: 17 0 [16] [<ffffffff802ab31d>] lookup_mnt+0x19/0x4c [1] [<ffffffff802a51df>] __d_path+0xae/0x14c
read as:
<lock name> <(write) contentiond> <read contentions>
(<contentions> <ip> <symbol>){,4}
The 4 points are the first 4 unique callsites that cause lock contention
for the specified lock class.
writing a 0 to /proc/lockdep_contentions clears the stats
Signed-off-by: Peter Zijlstra <[email protected]>
---
include/linux/lockdep.h | 14 +++++++
kernel/lockdep.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
kernel/lockdep_proc.c | 77 ++++++++++++++++++++++++++++++++++++++
kernel/mutex.c | 7 +++
kernel/rwsem.c | 20 ++++++++--
kernel/spinlock.c | 70 ++++++++++++++++++++++++++++-------
6 files changed, 266 insertions(+), 18 deletions(-)
Index: linux-2.6/include/linux/lockdep.h
===================================================================
--- linux-2.6.orig/include/linux/lockdep.h 2007-04-03 13:58:27.000000000 +0200
+++ linux-2.6/include/linux/lockdep.h 2007-05-19 10:26:44.000000000 +0200
@@ -16,6 +16,7 @@ struct task_struct;
#include <linux/list.h>
#include <linux/debug_locks.h>
#include <linux/stacktrace.h>
+#include <asm/atomic.h>
/*
* Lock-class usage-state bits:
@@ -71,6 +72,11 @@ struct lock_class_key {
struct lockdep_subclass_key subkeys[MAX_LOCKDEP_SUBCLASSES];
};
+struct lockdep_contention_point {
+ unsigned long ip;
+ atomic_t count;
+};
+
/*
* The lock-class itself:
*/
@@ -114,6 +120,10 @@ struct lock_class {
const char *name;
int name_version;
+
+ atomic_t read_contentions;
+ atomic_t write_contentions;
+ struct lockdep_contention_point contention_point[4];
};
/*
@@ -243,6 +253,9 @@ extern void lock_acquire(struct lockdep_
extern void lock_release(struct lockdep_map *lock, int nested,
unsigned long ip);
+extern void lock_contended(struct lockdep_map *lock, int read,
+ unsigned long ip);
+
# define INIT_LOCKDEP .lockdep_recursion = 0,
#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
@@ -259,6 +272,7 @@ static inline void lockdep_on(void)
# define lock_acquire(l, s, t, r, c, i) do { } while (0)
# define lock_release(l, n, i) do { } while (0)
+# define lock_contended(l, r, i) do { } while (0)
# define lockdep_init() do { } while (0)
# define lockdep_info() do { } while (0)
# define lockdep_init_map(lock, name, key, sub) do { (void)(key); } while (0)
Index: linux-2.6/kernel/lockdep.c
===================================================================
--- linux-2.6.orig/kernel/lockdep.c 2007-05-10 17:24:41.000000000 +0200
+++ linux-2.6/kernel/lockdep.c 2007-05-19 10:58:40.000000000 +0200
@@ -2261,6 +2261,33 @@ print_unlock_inbalance_bug(struct task_s
return 0;
}
+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 content 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;
+}
+
/*
* Common debugging checks for both nested and non-nested unlock:
*/
@@ -2401,6 +2428,59 @@ __lock_release(struct lockdep_map *lock,
check_chain_key(curr);
}
+static void
+__lock_contended(struct lockdep_map *lock, int read, unsigned long ip)
+{
+ struct task_struct *curr = current;
+ struct held_lock *hlock, *prev_hlock;
+ struct lock_class *class;
+ unsigned int depth;
+ int i;
+
+ class = lock->class_cache;
+ if (class)
+ goto found_it;
+
+ 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) {
+ class = hlock->class;
+ goto found_it;
+ }
+ prev_hlock = hlock;
+ }
+ print_lock_contention_bug(curr, lock, ip);
+ return;
+
+found_it:
+ if (read)
+ atomic_inc(&class->read_contentions);
+ else
+ atomic_inc(&class->write_contentions);
+
+ for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
+ if (class->contention_point[i].ip == 0) {
+ class->contention_point[i].ip = ip;
+ atomic_set(&class->contention_point[i].count, 1);
+ break;
+ }
+ if (class->contention_point[i].ip == ip) {
+ atomic_inc(&class->contention_point[i].count);
+ break;
+ }
+ }
+}
+
/*
* Check whether we follow the irq-flags state precisely:
*/
@@ -2473,6 +2553,22 @@ void lock_release(struct lockdep_map *lo
EXPORT_SYMBOL_GPL(lock_release);
+void lock_contended(struct lockdep_map *lock, int read, 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, read, ip);
+ current->lockdep_recursion = 0;
+ raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_contended);
+
/*
* 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 2007-05-10 10:19:03.000000000 +0200
+++ linux-2.6/kernel/mutex.c 2007-05-18 21:47:38.000000000 +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, 0, _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 2007-04-03 13:58:27.000000000 +0200
+++ linux-2.6/kernel/lockdep_proc.c 2007-05-19 10:50:18.000000000 +0200
@@ -15,6 +15,7 @@
#include <linux/seq_file.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
+#include <asm/uaccess.h>
#include "lockdep_internals.h"
@@ -342,6 +343,78 @@ static const struct file_operations proc
.release = seq_release,
};
+static int lockdep_contentions_show(struct seq_file *m, void *v)
+{
+ struct lock_class *class;
+
+ list_for_each_entry(class, &all_lock_classes, lock_entry) {
+ int r, w;
+
+ r = atomic_read(&class->read_contentions);
+ w = atomic_read(&class->write_contentions);
+
+ if (r || w) {
+ int i;
+ char sym[KSYM_SYMBOL_LEN];
+
+ seq_printf(m, "%s: %d %d", class->name, w, r);
+ for (i = 0; i < ARRAY_SIZE(class->contention_point);
+ i++) {
+ struct lockdep_contention_point *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 lockdep_contentions_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, lockdep_contentions_show, NULL);
+}
+
+ssize_t lockdep_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_lockdep_contentions_operations = {
+ .open = lockdep_contentions_open,
+ .write = lockdep_contentions_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
static int __init lockdep_proc_init(void)
{
struct proc_dir_entry *entry;
@@ -354,6 +427,10 @@ static int __init lockdep_proc_init(void
if (entry)
entry->proc_fops = &proc_lockdep_stats_operations;
+ entry = create_proc_entry("lockdep_contentions", S_IRUSR, NULL);
+ if (entry)
+ entry->proc_fops = &proc_lockdep_contentions_operations;
+
return 0;
}
Index: linux-2.6/kernel/rwsem.c
===================================================================
--- linux-2.6.orig/kernel/rwsem.c 2007-05-19 10:06:44.000000000 +0200
+++ linux-2.6/kernel/rwsem.c 2007-05-19 10:37:59.000000000 +0200
@@ -20,7 +20,10 @@ void down_read(struct rw_semaphore *sem)
might_sleep();
rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
- __down_read(sem);
+ if (!__down_read_trylock(sem)) {
+ lock_contended(&sem->dep_map, 1, _RET_IP_);
+ __down_read(sem);
+ }
}
EXPORT_SYMBOL(down_read);
@@ -47,7 +50,10 @@ void down_write(struct rw_semaphore *sem
might_sleep();
rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
- __down_write(sem);
+ if (!__down_write_trylock(sem)) {
+ lock_contended(&sem->dep_map, 0, _RET_IP_);
+ __down_write(sem);
+ }
}
EXPORT_SYMBOL(down_write);
@@ -111,7 +117,10 @@ void down_read_nested(struct rw_semaphor
might_sleep();
rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
- __down_read(sem);
+ if (!__down_read_trylock(sem)) {
+ lock_contended(&sem->dep_map, 1, _RET_IP_);
+ __down_read(sem);
+ }
}
EXPORT_SYMBOL(down_read_nested);
@@ -130,7 +139,10 @@ void down_write_nested(struct rw_semapho
might_sleep();
rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
- __down_write_nested(sem, subclass);
+ if (!__down_write_trylock(sem)) {
+ lock_contended(&sem->dep_map, 0, _RET_IP_);
+ __down_write_nested(sem, subclass);
+ }
}
EXPORT_SYMBOL(down_write_nested);
Index: linux-2.6/kernel/spinlock.c
===================================================================
--- linux-2.6.orig/kernel/spinlock.c 2007-05-10 10:19:03.000000000 +0200
+++ linux-2.6/kernel/spinlock.c 2007-05-19 10:20:47.000000000 +0200
@@ -72,7 +72,10 @@ void __lockfunc _read_lock(rwlock_t *loc
{
preempt_disable();
rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
- _raw_read_lock(lock);
+ if (!_raw_read_trylock(lock)) {
+ lock_contended(&lock->dep_map, 1, _RET_IP_);
+ _raw_read_lock(lock);
+ }
}
EXPORT_SYMBOL(_read_lock);
@@ -89,7 +92,10 @@ unsigned long __lockfunc _spin_lock_irqs
* that interrupts are not re-enabled during lock-acquire:
*/
#ifdef CONFIG_PROVE_LOCKING
- _raw_spin_lock(lock);
+ if (!_raw_spin_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_spin_lock(lock);
+ }
#else
_raw_spin_lock_flags(lock, &flags);
#endif
@@ -102,7 +108,10 @@ void __lockfunc _spin_lock_irq(spinlock_
local_irq_disable();
preempt_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
- _raw_spin_lock(lock);
+ if (!_raw_spin_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_spin_lock(lock);
+ }
}
EXPORT_SYMBOL(_spin_lock_irq);
@@ -111,7 +120,10 @@ 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);
+ if (!_raw_spin_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_spin_lock(lock);
+ }
}
EXPORT_SYMBOL(_spin_lock_bh);
@@ -122,7 +134,10 @@ 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);
+ if (!_raw_read_trylock(lock)) {
+ lock_contended(&lock->dep_map, 1, _RET_IP_);
+ _raw_read_lock(lock);
+ }
return flags;
}
EXPORT_SYMBOL(_read_lock_irqsave);
@@ -132,7 +147,10 @@ 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);
+ if (!_raw_read_trylock(lock)) {
+ lock_contended(&lock->dep_map, 1, _RET_IP_);
+ _raw_read_lock(lock);
+ }
}
EXPORT_SYMBOL(_read_lock_irq);
@@ -141,7 +159,10 @@ 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);
+ if (!_raw_read_trylock(lock)) {
+ lock_contended(&lock->dep_map, 1, _RET_IP_);
+ _raw_read_lock(lock);
+ }
}
EXPORT_SYMBOL(_read_lock_bh);
@@ -152,7 +173,10 @@ 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);
+ if (!_raw_write_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_write_lock(lock);
+ }
return flags;
}
EXPORT_SYMBOL(_write_lock_irqsave);
@@ -162,7 +186,10 @@ 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);
+ if (!_raw_write_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_write_lock(lock);
+ }
}
EXPORT_SYMBOL(_write_lock_irq);
@@ -171,7 +198,10 @@ 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);
+ if (!_raw_write_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_write_lock(lock);
+ }
}
EXPORT_SYMBOL(_write_lock_bh);
@@ -179,7 +209,10 @@ void __lockfunc _spin_lock(spinlock_t *l
{
preempt_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
- _raw_spin_lock(lock);
+ if (!_raw_spin_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_spin_lock(lock);
+ }
}
EXPORT_SYMBOL(_spin_lock);
@@ -188,7 +221,10 @@ void __lockfunc _write_lock(rwlock_t *lo
{
preempt_disable();
rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
- _raw_write_lock(lock);
+ if (!_raw_write_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_write_lock(lock);
+ }
}
EXPORT_SYMBOL(_write_lock);
@@ -289,7 +325,10 @@ void __lockfunc _spin_lock_nested(spinlo
{
preempt_disable();
spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
- _raw_spin_lock(lock);
+ if (!_raw_spin_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_spin_lock(lock);
+ }
}
EXPORT_SYMBOL(_spin_lock_nested);
@@ -306,7 +345,10 @@ unsigned long __lockfunc _spin_lock_irqs
* that interrupts are not re-enabled during lock-acquire:
*/
#ifdef CONFIG_PROVE_SPIN_LOCKING
- _raw_spin_lock(lock);
+ if (!_raw_spin_trylock(lock)) {
+ lock_contended(&lock->dep_map, 0, _RET_IP_);
+ _raw_spin_lock(lock);
+ }
#else
_raw_spin_lock_flags(lock, &flags);
#endif
-
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