Commit-ID: bcc9a76d5ac426bc45c9e863b1830347827ca77a
Gitweb: http://git.kernel.org/tip/bcc9a76d5ac426bc45c9e863b1830347827ca77a
Author: Waiman Long <longman@xxxxxxxxxx>
AuthorDate: Sat, 21 Jan 2017 21:33:35 -0500
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sun, 22 Jan 2017 09:54:00 +0100
locking/rwsem: Reinit wake_q after use
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 <longman@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1485052415-9611-1-git-send-email-longman@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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 f4f9d32..4e62b37 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1021,6 +1021,12 @@ 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 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
* 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 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
* for attempting rwsem_try_write_lock().
*/
wake_up_q(&wake_q);
+
+ /*
+ * Reinitialize wake_q after use.
+ */
+ wake_q_init(&wake_q);
}
} else
--
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