Skip to content

Commit

Permalink
locking/rwsem: Move owner setting code from rwsem.c to rwsem.h
Browse files Browse the repository at this point in the history 
Move all the owner setting code closer to the rwsem-xadd fast paths
directly within rwsem.h file as well as in the slowpaths where owner
setting is done after acquring the lock. This will enable us to add
DEBUG_RWSEMS check in a later patch to make sure that read lock is
really acquired when rwsem_down_read_failed() returns, for instance.

Signed-off-by: Waiman Long <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Acked-by: Davidlohr Bueso <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Will Deacon <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
  • Loading branch information
@Waiman-Long
Waiman-Long authored and Ingo Molnar committed Apr 10, 2019
1 parent eecec78 commit c7580c1
Show file tree
Hide file tree
Showing 3 changed files with 20 additions and 22 deletions.
6 changes: 3 additions & 3 deletions kernel/locking/rwsem-xadd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
}
Expand Down Expand Up @@ -441,6 +440,7 @@ __rwsem_down_read_failed_common(struct rw_semaphore *sem, int state)
*/
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;
Expand Down
19 changes: 2 additions & 17 deletions kernel/locking/rwsem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -39,7 +38,6 @@ int __sched down_read_killable(struct rw_semaphore *sem)
return -EINTR;
}

rwsem_set_reader_owned(sem);
return 0;
}

Expand All @@ -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;
}

Expand All @@ -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);
Expand All @@ -88,7 +83,6 @@ int __sched down_write_killable(struct rw_semaphore *sem)
return -EINTR;
}

rwsem_set_owner(sem);
return 0;
}

Expand All @@ -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;
}
Expand All @@ -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);
}

Expand All @@ -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);
}

Expand All @@ -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);
}

Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -208,7 +194,6 @@ int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
return -EINTR;
}

rwsem_set_owner(sem);
return 0;
}

Expand Down
17 changes: 15 additions & 2 deletions kernel/locking/rwsem.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -160,15 +160,18 @@ 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)
{
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;
}

Expand All @@ -182,6 +185,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
do {
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
tmp + RWSEM_ACTIVE_READ_BIAS)) {
rwsem_set_reader_owned(sem);
return 1;
}
} while (tmp >= 0);
Expand All @@ -199,6 +203,7 @@ 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)
Expand All @@ -210,6 +215,7 @@ 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;
}

Expand All @@ -219,7 +225,11 @@ 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;
}

/*
Expand All @@ -229,6 +239,7 @@ 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);
Expand All @@ -239,6 +250,7 @@ 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);
Expand All @@ -259,6 +271,7 @@ 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);
}

0 comments on commit c7580c1

Please sign in to comment.