[patch V4 19/68] locking/rtmutex: Provide rt_wake_q and helpers

Thomas Gleixner
2021-08-11T12:24:07Z

To handle the difference of wakeups for regular sleeping locks (mutex,
rtmutex, rw_semaphore) and the wakeups for 'sleeping' spin/rwlocks on
PREEMPT_RT enabled kernels correctly, it is required to provide a
wake_q construct which allows to keep them separate.

Provide a wrapper around wake_q and the required helpers, which will be
extended with the state handling later.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V2: Rename according to PeterZ
---
kernel/locking/rtmutex.c | 15 +++++++++++++++
kernel/locking/rtmutex_common.h | 14 ++++++++++++++
2 files changed, 29 insertions(+)
---
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -347,6 +347,21 @@ static __always_inline void rt_mutex_adj
rt_mutex_setprio(p, pi_task);
}

+/* RT mutex specific wake_q wrappers */
+static __always_inline void rt_mutex_wake_q_add(struct rt_wake_q_head *wqh,
+ struct rt_mutex_waiter *w)
+{
+ wake_q_add(&wqh->head, w->task);
+}
+
+static __always_inline void rt_mutex_wake_up_q(struct rt_wake_q_head *wqh)
+{
+ wake_up_q(&wqh->head);
+
+ /* Pairs with preempt_disable() in mark_wakeup_next_waiter() */
+ preempt_enable();
+}
+
/*
* Deadlock detection is conditional:
*
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -39,6 +39,20 @@ struct rt_mutex_waiter {
u64 deadline;
};

+/**
+ * rt_wake_q_head - Wrapper around regular wake_q_head to support
+ * "sleeping" spinlocks on RT
+ * @head: The regular wake_q_head for sleeping lock variants
+ */
+struct rt_wake_q_head {
+ struct wake_q_head head;
+};
+
+#define DEFINE_RT_WAKE_Q(name) \
+ struct rt_wake_q_head name = { \
+ .head = WAKE_Q_HEAD_INITIALIZER(name.head), \
+ }
+
/*
* PI-futex support (proxy locking functions, etc.):
*/