[RFC 3/4] locking/rwsem: additional lock information when dumping locks

Sasha Levin
2015-01-12T14:57:48Z

Show the counter and the owner of the lock when dumping held locks in the
system.

This is useful to figure out who really holds a lock and how many waiters
it has.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---
include/linux/lockdep.h | 2 +-
include/linux/rwsem.h | 3 ++-
kernel/locking/lockdep.c | 5 +++++
kernel/locking/rwsem-spinlock.c | 7 ++++++-
kernel/locking/rwsem-xadd.c | 2 +-
kernel/locking/rwsem.c | 15 +++++++++++++++
6 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index cab929b..4527f99 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -143,7 +143,7 @@ struct lock_class_stats lock_stats(struct lock_class *class);
void clear_lock_stats(struct lock_class *class);
#endif

-enum LOCK_TYPE { LOCKTYPE_NONE, LOCKTYPE_MUTEX, };
+enum LOCK_TYPE { LOCKTYPE_NONE, LOCKTYPE_MUTEX, LOCKTYPE_RWSEM, };

/*
* Map the lock object (the lock instance) to the lock-class object.
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 8f498cd..68732af 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -60,7 +60,8 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
/* Common initializer macros and functions */

#ifdef CONFIG_DEBUG_LOCK_ALLOC
-# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
+extern void rwsem_print_debug(const struct rw_semaphore *sem);
+# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname, .type = LOCKTYPE_RWSEM }
#else
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 07c337d..e75f83b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -511,6 +511,7 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
static void get_lock_info(enum LOCK_TYPE t, struct lockdep_map *map)
{
struct mutex *mtx;
+ struct rw_semaphore *rw;

switch (t) {
case LOCKTYPE_NONE: break;
@@ -518,6 +519,10 @@ static void get_lock_info(enum LOCK_TYPE t, struct lockdep_map *map)
mtx = container_of(map, struct mutex, dep_map);
mutex_print_debug(mtx);
break;
+ case LOCKTYPE_RWSEM:
+ rw = container_of(map, struct rw_semaphore, dep_map);
+ rwsem_print_debug(rw);
+ break;
}
}

diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c
index 2c93571..b07029e 100644
--- a/kernel/locking/rwsem-spinlock.c
+++ b/kernel/locking/rwsem-spinlock.c
@@ -44,7 +44,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
* Make sure we are not reinitializing a held semaphore:
*/
debug_check_no_locks_freed((void *)sem, sizeof(*sem));
- lockdep_init_map(&sem->dep_map, name, key, 0);
+ lockdep_init_map_type(&sem->dep_map, name, key, 0, LOCKTYPE_RWSEM);
#endif
sem->count = 0;
raw_spin_lock_init(&sem->wait_lock);
@@ -294,3 +294,8 @@ void __downgrade_write(struct rw_semaphore *sem)
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
}

+void rwsem_print_debug(const struct rw_semaphore *sem)
+{
+ printk("RWsem: count: %l\n", sem->count);
+}
+EXPORT_SYMBOL_GPL(rwsem_print_debug);
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index 7628c3f..8b00656 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -77,7 +77,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
* Make sure we are not reinitializing a held semaphore:
*/
debug_check_no_locks_freed((void *)sem, sizeof(*sem));
- lockdep_init_map(&sem->dep_map, name, key, 0);
+ lockdep_init_map_type(&sem->dep_map, name, key, 0, LOCKTYPE_RWSEM);
#endif
sem->count = RWSEM_UNLOCKED_VALUE;
raw_spin_lock_init(&sem->wait_lock);
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index e2d3bc7..24183cc 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -181,6 +181,21 @@ void up_read_non_owner(struct rw_semaphore *sem)

EXPORT_SYMBOL(up_read_non_owner);

+void rwsem_print_debug(const struct rw_semaphore *sem)
+{
+ const char *owner = "Unknown";
+
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+ if (sem->owner)
+ owner = sem->owner->comm;
+ else
+ owner = "None";
+#endif
+
+ printk("RWsem: count: %ld owner: %s\n", sem->count, owner);
+}
+EXPORT_SYMBOL_GPL(rwsem_print_debug);
+
#endif

--
1.7.10.4