linux-kernel - [patch 24/50] locking/spinlock: Provide RT specific spinlock type

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Message-Id: <20210713160748.288862984@linutronix.de>
Date:   Tue, 13 Jul 2021 17:11:18 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Davidlohr Bueso <dave@...olabs.net>
Subject: [patch 24/50] locking/spinlock: Provide RT specific spinlock type

From: Thomas Gleixner <tglx@...utronix.de>

RT replaces spinlocks with a simple wrapper around a rtmutex which turns
spinlocks on RT into 'sleeping' spinlocks. The actual implementation of the
spinlock API differs from a regular rtmutex as it does neither handle
timeouts nor signals and it is state preserving accross the lock operation.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 include/linux/spinlock_types.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
---
diff --git a/include/linux/spinlock_types.h b/include/linux/spinlock_types.h
index 7c8107c280c0..98d498f9e4fc 100644
--- a/include/linux/spinlock_types.h
+++ b/include/linux/spinlock_types.h
@@ -51,6 +51,9 @@
 
 #define DEFINE_RAW_SPINLOCK(x)	raw_spinlock_t x = __RAW_SPIN_LOCK_UNLOCKED(x)
 
+#ifndef CONFIG_PREEMPT_RT
+
+/* Non PREEMPT_RT kernels map spinlock to raw_spinlock */
 typedef struct spinlock {
 	union {
 		struct raw_spinlock rlock;
@@ -79,6 +82,29 @@ typedef struct spinlock {
 
 #define DEFINE_SPINLOCK(x)	spinlock_t x = __SPIN_LOCK_UNLOCKED(x)
 
+#else /* !CONFIG_PREEMPT_RT */
+
+/* PREEMPT_RT kernels map spinlock to rt_mutex */
+#include <linux/rtmutex.h>
+
+typedef struct spinlock {
+	struct rt_mutex		lock;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map	dep_map;
+#endif
+} spinlock_t;
+
+#define __SPIN_LOCK_UNLOCKED(name)				\
+	{							\
+		.lock = __RT_MUTEX_INITIALIZER(name.lock),	\
+		SPIN_DEP_MAP_INIT(name)				\
+	}
+
+#define DEFINE_SPINLOCK(name)					\
+	spinlock_t name = __SPIN_LOCK_UNLOCKED(name)
+
+#endif /* CONFIG_PREEMPT_RT */
+
 #include <linux/rwlock_types.h>
 
 #endif /* __LINUX_SPINLOCK_TYPES_H */