提交 c8fe8b05 编写于 作者: W Waiman Long 提交者: Peter Zijlstra

locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath()

The atomic count value right after reader count increment can be useful
to determine the rwsem state at trylock time. So the count value is
passed down to rwsem_down_read_slowpath() to be used when appropriate.
Signed-off-by: NWaiman Long <longman@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NDavidlohr Bueso <dbueso@suse.de>
Link: https://lkml.kernel.org/r/20201121041416.12285-2-longman@redhat.com
上级 c995e638
...@@ -270,14 +270,14 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem) ...@@ -270,14 +270,14 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
owner | RWSEM_NONSPINNABLE)); owner | RWSEM_NONSPINNABLE));
} }
static inline bool rwsem_read_trylock(struct rw_semaphore *sem) static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
{ {
long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count); *cntp = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
if (WARN_ON_ONCE(cnt < 0)) if (WARN_ON_ONCE(*cntp < 0))
rwsem_set_nonspinnable(sem); rwsem_set_nonspinnable(sem);
if (!(cnt & RWSEM_READ_FAILED_MASK)) { if (!(*cntp & RWSEM_READ_FAILED_MASK)) {
rwsem_set_reader_owned(sem); rwsem_set_reader_owned(sem);
return true; return true;
} }
...@@ -1008,9 +1008,9 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable) ...@@ -1008,9 +1008,9 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
* Wait for the read lock to be granted * Wait for the read lock to be granted
*/ */
static struct rw_semaphore __sched * static struct rw_semaphore __sched *
rwsem_down_read_slowpath(struct rw_semaphore *sem, int state) rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state)
{ {
long count, adjustment = -RWSEM_READER_BIAS; long adjustment = -RWSEM_READER_BIAS;
struct rwsem_waiter waiter; struct rwsem_waiter waiter;
DEFINE_WAKE_Q(wake_q); DEFINE_WAKE_Q(wake_q);
bool wake = false; bool wake = false;
...@@ -1356,8 +1356,10 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem) ...@@ -1356,8 +1356,10 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
*/ */
static inline int __down_read_common(struct rw_semaphore *sem, int state) static inline int __down_read_common(struct rw_semaphore *sem, int state)
{ {
if (!rwsem_read_trylock(sem)) { long count;
if (IS_ERR(rwsem_down_read_slowpath(sem, state)))
if (!rwsem_read_trylock(sem, &count)) {
if (IS_ERR(rwsem_down_read_slowpath(sem, count, state)))
return -EINTR; return -EINTR;
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
} }
......
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