diff options
| -rw-r--r-- | lib/rwsem.c | 29 |
1 files changed, 8 insertions, 21 deletions
diff --git a/lib/rwsem.c b/lib/rwsem.c index c73bd96dc30c..2360bf204098 100644 --- a/lib/rwsem.c +++ b/lib/rwsem.c @@ -143,20 +143,12 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type) } /* Try to get write sem, caller holds sem->wait_lock: */ -static int try_get_writer_sem(struct rw_semaphore *sem, - struct rwsem_waiter *waiter) +static int try_get_writer_sem(struct rw_semaphore *sem) { - struct rwsem_waiter *fwaiter; long oldcount, adjustment; - /* only steal when first waiter is writing */ - fwaiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list); - if (fwaiter->type != RWSEM_WAITING_FOR_WRITE) - return 0; - adjustment = RWSEM_ACTIVE_WRITE_BIAS; - /* Only one waiter in the queue: */ - if (fwaiter == waiter && waiter->list.next == &sem->wait_list) + if (list_is_singular(&sem->wait_list)) adjustment -= RWSEM_WAITING_BIAS; try_again_write: @@ -233,23 +225,18 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) /* we're now waiting on the lock, but no longer actively locking */ count = rwsem_atomic_update(adjustment, sem); - /* If there are no active locks, wake the front queued process(es) up. - * - * Alternatively, if we're called from a failed down_write(), there - * were already threads queued before us and there are no active - * writers, the lock must be read owned; so we try to wake any read - * locks that were queued ahead of us. */ - if (count == RWSEM_WAITING_BIAS) - sem = __rwsem_do_wake(sem, RWSEM_WAKE_NO_ACTIVE); - else if (count > RWSEM_WAITING_BIAS && - adjustment == -RWSEM_ACTIVE_WRITE_BIAS) + /* If there were already threads queued before us and there are no + * active writers, the lock must be read owned; so we try to wake + * any read locks that were queued ahead of us. */ + if (count > RWSEM_WAITING_BIAS && + adjustment == -RWSEM_ACTIVE_WRITE_BIAS) sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED); /* wait until we successfully acquire the lock */ while (true) { set_task_state(tsk, TASK_UNINTERRUPTIBLE); - if (try_get_writer_sem(sem, &waiter)) + if (try_get_writer_sem(sem)) break; raw_spin_unlock_irq(&sem->wait_lock); |