In __rwsem_down_write_failed_common(), the same wake_q variable name
is defined twice, with the inner wake_q hiding the one in outer scope.
We can either use different names for the two wake_q's. Even better,
we can use the same wake_q twice, if necessary. To enable the latter
change, we need to define a new helper function wake_q_init() to
enable reinitalization of wake_q after use.
Signed-off-by: Waiman Long <long...@redhat.com>
---
include/linux/sched.h | 6 ++++++
kernel/locking/rwsem-xadd.c | 7 +++++--
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8a9bbb6..3640bde 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1019,6 +1019,12 @@ struct wake_q_head {
#define DEFINE_WAKE_Q(name) \
struct wake_q_head name = { WAKE_Q_TAIL, &name.first }
+static inline void wake_q_init(struct wake_q_head *head)
+{
+ head->first = WAKE_Q_TAIL;
+ head->lastp = &head->first;
+}
+
extern void wake_q_add(struct wake_q_head *head,
struct task_struct *task);
extern void wake_up_q(struct wake_q_head *head);
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index a3a381a..2ad8d8d 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -502,8 +502,6 @@ static inline bool rwsem_has_spinner(struct rw_semaphore
*sem)
* wake any read locks that were queued ahead of us.
*/
if (count > RWSEM_WAITING_BIAS) {
- DEFINE_WAKE_Q(wake_q);
-
__rwsem_mark_wake(sem, RWSEM_WAKE_READERS, &wake_q);
/*
* The wakeup is normally called _after_ the wait_lock
@@ -513,6 +511,11 @@ static inline bool rwsem_has_spinner(struct rw_semaphore
*sem)
* for attempting rwsem_try_write_lock().
*/
wake_up_q(&wake_q);
+
+ /*
+ * Reinitialize wake_q after use.
+ */
+ wake_q_init(&wake_q);
}
} else
--
1.8.3.1
