locking/rtmutex: Provide rt_wake_q_head and helpers

To handle the difference between 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_head construct which allows to keep them separate.

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

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.139337655@linutronix.de

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index c13b9b8..35f7685 100644 (file)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -347,6 +347,21 @@ static __always_inline void rt_mutex_adjust_prio(struct task_struct *p)
        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:
  *

diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index fcc55de..9e2f1db 100644 (file)
--- 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.):
  */