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-rw-r--r--lib/rwsem.c29
1 files changed, 8 insertions, 21 deletions
diff --git a/lib/rwsem.c b/lib/rwsem.c
index c73bd96dc30..2360bf20409 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);