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-rw-r--r--lib/rwsem.c26
1 files changed, 12 insertions, 14 deletions
diff --git a/lib/rwsem.c b/lib/rwsem.c
index 0d50e46d5b0c..9a675fa9d78e 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -68,20 +68,17 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
signed long woken, loop, adjustment;
waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
- if (waiter->type != RWSEM_WAITING_FOR_WRITE)
- goto readers_only;
-
- if (wake_type == RWSEM_WAKE_READ_OWNED)
- /* Another active reader was observed, so wakeup is not
- * likely to succeed. Save the atomic op.
- */
+ if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
+ if (wake_type != RWSEM_WAKE_READ_OWNED)
+ /* Wake writer at the front of the queue, but do not
+ * grant it the lock yet as we want other writers
+ * to be able to steal it. Readers, on the other hand,
+ * will block as they will notice the queued writer.
+ */
+ wake_up_process(waiter->task);
goto out;
+ }
- /* Wake up the writing waiter and let the task grab the sem: */
- wake_up_process(waiter->task);
- goto out;
-
- readers_only:
/* If we come here from up_xxxx(), another thread might have reached
* rwsem_down_failed_common() before we acquired the spinlock and
* woken up a waiter, making it now active. We prefer to check for
@@ -125,7 +122,8 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
rwsem_atomic_add(adjustment, sem);
next = sem->wait_list.next;
- for (loop = woken; loop > 0; loop--) {
+ loop = woken;
+ do {
waiter = list_entry(next, struct rwsem_waiter, list);
next = waiter->list.next;
tsk = waiter->task;
@@ -133,7 +131,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
- }
+ } while (--loop);
sem->wait_list.next = next;
next->prev = &sem->wait_list;

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