The rwsem wakeup logic has been modified by commit d3681e269fff
("locking/rwsem: Wake up almost all readers in wait queue") to wake up
all readers in the wait queue if the first waiter is a reader. In the
case of RWSEM_WAKE_READ_OWNED, not all readers can be woken up if the
first waiter happens to be a writer. Complete the logic by waking up
all readers even for this case.
Signed-off-by: Waiman Long <long...@redhat.com>
---
kernel/locking/rwsem.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 930dd4af3639..23654e3950b5 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -426,7 +426,12 @@ static void rwsem_mark_wake(struct rw_semaphore *sem,
lockevent_inc(rwsem_wake_writer);
}
- return;
+ /*
+ * If rwsem has already been owned by reader, wake up other
+ * readers in the wait queue even if first one is a writer.
+ */
+ if (wake_type != RWSEM_WAKE_READ_OWNED)
+ return;
}
/*
@@ -1052,8 +1057,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int
state, long count)
if (rwsem_optimistic_spin(sem, false)) {
/* rwsem_optimistic_spin() implies ACQUIRE on success */
/*
- * Wake up other readers in the wait list if the front
- * waiter is a reader.
+ * Wake up other readers in the wait queue.
*/
wake_readers:
if ((atomic_long_read(&sem->count) & RWSEM_FLAG_WAITERS)) {
--
2.18.1
