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:
<class name> <(write) contentions> <read contentions>
Followed by another three columns per contention point:
<contentions from this point> <IP> <symbol name>
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] [<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
Signed-off-by: Peter Zijlstra <[email protected]>
---
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 <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 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 <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,
};
+#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
+
+
--
-
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