The setting of owner field is specific to rwsem-xadd code, it is not needed
for rwsem-spinlock. This patch moves all the owner setting code closer
to the rwsem-xadd fast paths directly within rwsem.h file.
For __down_read() and __down_read_killable(), it is assumed that
rwsem will be marked as reader-owned when the functions return. That
is currently true except in the transient case that the waiter queue
just becomes empty. So a rwsem_set_reader_owned() call is added for
this case. The __rwsem_set_reader_owned() call in __rwsem_mark_wake()
is now necessary.
Signed-off-by: Waiman Long <long...@redhat.com>
---
kernel/locking/rwsem-xadd.c | 6 +++---
kernel/locking/rwsem.c | 19 ++-----------------
kernel/locking/rwsem.h | 17 +++++++++++++++--
3 files changed, 20 insertions(+), 22 deletions(-)
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index 0d518b5..c213869 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -176,9 +176,8 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem,
goto try_reader_grant;
}
/*
- * It is not really necessary to set it to reader-owned here,
- * but it gives the spinners an early indication that the
- * readers now have the lock.
+ * Set it to reader-owned to give spinners an early
+ * indication that readers now have the lock.
*/
__rwsem_set_reader_owned(sem, waiter->task);
}
@@ -441,6 +440,7 @@ static inline bool rwsem_has_spinner(struct rw_semaphore
*sem)
*/
if (atomic_long_read(&sem->count) >= 0) {
raw_spin_unlock_irq(&sem->wait_lock);
+ rwsem_set_reader_owned(sem);
return sem;
}
adjustment += RWSEM_WAITING_BIAS;
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index e586f0d..59e5848 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -24,7 +24,6 @@ void __sched down_read(struct rw_semaphore *sem)
rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
- rwsem_set_reader_owned(sem);
}
EXPORT_SYMBOL(down_read);
@@ -39,7 +38,6 @@ int __sched down_read_killable(struct rw_semaphore *sem)
return -EINTR;
}
- rwsem_set_reader_owned(sem);
return 0;
}
@@ -52,10 +50,8 @@ int down_read_trylock(struct rw_semaphore *sem)
{
int ret = __down_read_trylock(sem);
- if (ret == 1) {
+ if (ret == 1)
rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
- rwsem_set_reader_owned(sem);
- }
return ret;
}
@@ -70,7 +66,6 @@ void __sched down_write(struct rw_semaphore *sem)
rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
- rwsem_set_owner(sem);
}
EXPORT_SYMBOL(down_write);
@@ -88,7 +83,6 @@ int __sched down_write_killable(struct rw_semaphore *sem)
return -EINTR;
}
- rwsem_set_owner(sem);
return 0;
}
@@ -101,10 +95,8 @@ int down_write_trylock(struct rw_semaphore *sem)
{
int ret = __down_write_trylock(sem);
- if (ret == 1) {
+ if (ret == 1)
rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
- rwsem_set_owner(sem);
- }
return ret;
}
@@ -119,7 +111,6 @@ void up_read(struct rw_semaphore *sem)
rwsem_release(&sem->dep_map, 1, _RET_IP_);
DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED));
- rwsem_clear_reader_owned(sem);
__up_read(sem);
}
@@ -133,7 +124,6 @@ void up_write(struct rw_semaphore *sem)
rwsem_release(&sem->dep_map, 1, _RET_IP_);
DEBUG_RWSEMS_WARN_ON(sem->owner != current);
- rwsem_clear_owner(sem);
__up_write(sem);
}
@@ -147,7 +137,6 @@ void downgrade_write(struct rw_semaphore *sem)
lock_downgrade(&sem->dep_map, _RET_IP_);
DEBUG_RWSEMS_WARN_ON(sem->owner != current);
- rwsem_set_reader_owned(sem);
__downgrade_write(sem);
}
@@ -161,7 +150,6 @@ void down_read_nested(struct rw_semaphore *sem, int
subclass)
rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
- rwsem_set_reader_owned(sem);
}
EXPORT_SYMBOL(down_read_nested);
@@ -172,7 +160,6 @@ void _down_write_nest_lock(struct rw_semaphore *sem, struct
lockdep_map *nest)
rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
- rwsem_set_owner(sem);
}
EXPORT_SYMBOL(_down_write_nest_lock);
@@ -193,7 +180,6 @@ void down_write_nested(struct rw_semaphore *sem, int
subclass)
rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
- rwsem_set_owner(sem);
}
EXPORT_SYMBOL(down_write_nested);
@@ -208,7 +194,6 @@ int __sched down_write_killable_nested(struct rw_semaphore
*sem, int subclass)
return -EINTR;
}
- rwsem_set_owner(sem);
return 0;
}
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
index 067e265..f568391 100644
--- a/kernel/locking/rwsem.h
+++ b/kernel/locking/rwsem.h
@@ -161,6 +161,8 @@ static inline void __down_read(struct rw_semaphore *sem)
{
if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0))
rwsem_down_read_failed(sem);
+ else
+ rwsem_set_reader_owned(sem);
}
static inline int __down_read_killable(struct rw_semaphore *sem)
@@ -168,8 +170,9 @@ static inline int __down_read_killable(struct rw_semaphore
*sem)
if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) {
if (IS_ERR(rwsem_down_read_failed_killable(sem)))
return -EINTR;
+ } else {
+ rwsem_set_reader_owned(sem);
}
-
return 0;
}
@@ -180,6 +183,7 @@ static inline int __down_read_trylock(struct rw_semaphore
*sem)
while ((tmp = atomic_long_read(&sem->count)) >= 0) {
if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
tmp + RWSEM_ACTIVE_READ_BIAS)) {
+ rwsem_set_reader_owned(sem);
return 1;
}
}
@@ -197,6 +201,7 @@ static inline void __down_write(struct rw_semaphore *sem)
&sem->count);
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
rwsem_down_write_failed(sem);
+ rwsem_set_owner(sem);
}
static inline int __down_write_killable(struct rw_semaphore *sem)
@@ -208,6 +213,7 @@ static inline int __down_write_killable(struct rw_semaphore
*sem)
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
if (IS_ERR(rwsem_down_write_failed_killable(sem)))
return -EINTR;
+ rwsem_set_owner(sem);
return 0;
}
@@ -217,7 +223,11 @@ static inline int __down_write_trylock(struct rw_semaphore
*sem)
tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
- return tmp == RWSEM_UNLOCKED_VALUE;
+ if (tmp == RWSEM_UNLOCKED_VALUE) {
+ rwsem_set_owner(sem);
+ return true;
+ }
+ return false;
}
/*
@@ -227,6 +237,7 @@ static inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
+ rwsem_clear_reader_owned(sem);
tmp = atomic_long_dec_return_release(&sem->count);
if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
rwsem_wake(sem);
@@ -237,6 +248,7 @@ static inline void __up_read(struct rw_semaphore *sem)
*/
static inline void __up_write(struct rw_semaphore *sem)
{
+ rwsem_clear_owner(sem);
if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
&sem->count) < 0))
rwsem_wake(sem);
@@ -257,6 +269,7 @@ static inline void __downgrade_write(struct rw_semaphore
*sem)
* write side. As such, rely on RELEASE semantics.
*/
tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count);
+ rwsem_set_reader_owned(sem);
if (tmp < 0)
rwsem_downgrade_wake(sem);
}
--
1.8.3.1
