linux-kernel - [tip: locking/core] locking/rtmutex: Provide rt_wake_q

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Date:   Tue, 17 Aug 2021 20:14:26 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/rtmutex: Provide rt_wake_q_head and helpers

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     b576e640ce5e22673e12949cf14ae3cb18d9b859
Gitweb:        https://git.kernel.org/tip/b576e640ce5e22673e12949cf14ae3cb18d9b859
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Sun, 15 Aug 2021 23:28:08 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 17 Aug 2021 17:18:15 +02:00

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@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20210815211303.139337655@linutronix.de
---
 kernel/locking/rtmutex.c        | 15 +++++++++++++++
 kernel/locking/rtmutex_common.h | 14 ++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index c13b9b8..35f7685 100644
--- 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
--- 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.):
  */